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  • 101.
    Liu, J.
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Tan, M. -J
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Castagne, S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Aue-u-lan, Y.
    Singapore Institute of Manufacturing Technology.
    Fong, K. -S
    Singapore Institute of Manufacturing Technology.
    Jarfors, A. E. W.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Investigation of process parameters in superplastic forming of mechanical pre-formed sheet by FEM2010Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 447-448, s. 437-441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional superplastic forming has been applied in automotive and aerospace industries for a few decades. Recently, superplastic forming combined with mechanical pre-forming process has been reported to be capable of forming non-superplastic AA5083 at 400°C to a surface expansion of 200 % [1]. In this paper, finite element modeling (FEM) was used to develop the combined forming process by using the non-superplastic material AA5083-O. The simulation follows the experimental sequence and was divided into two phases (mechanical pre-forming and superplastic forming). A conventional creep equation based on tensile test data was adopted as a material model for the simulation. The pressure cycle and forming time was simulated according to the actual process route. The thickness distributions obtained from simulation validated the capability of the model to be used for this case. The influence of different parameters, such as holder force, friction, and punch depth was investigated by comparing the final sheet thickness and level of material draw-in. It was found that the punch depth played a significant effect on the uniformity of thickness distribution, from which a more uniform formed part can be obtained by using the punch with higher depth during mechanical pre-forming phase. © (2010) Trans Tech Publications.

  • 102.
    Liu, J.
    et al.
    Sch. of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Tan, M. -J
    Sch. of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Castagne, S.
    Sch. of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Aue-U-Lan, Y.
    Singapore Institute of Manufacturing Technology.
    Jarfors, A. E. W.
    Singapore Institute of Manufacturing Technology.
    Fong, K. -S
    Singapore Institute of Manufacturing Technology.
    Bayraktar, E.
    Supmeca-Paris, Mechanical Engineering School, France.
    Finite element modeling of a non-isothermal superplastic-like forming process2010Inngår i: AIP Conference Proceedings, Paris, 2010, Vol. 1315, s. 377-382Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Conventional superplastic forming (SPF) has been modified to increase the productivity and reduce some of the drawbacks, such as high forming temperature and high percentage thinning, to suit the automotive industries. One of the modifications was to combine between the conventional SPF and the use of a mechanical preformed blank to form the non-superplastic grade aluminum alloy (AA5083-O). The requirement of high temperature usually results in microstructural defects during forming process. In this paper, finite element modeling was adopted to investigate the superplastic-like forming process using the non-isothermal heating system. In the simulation, two phases (mechanical pre-forming and gas blow for ming) of the process were conducted under different temperatures, where the material was mechanically drawn into the die cavity at 200°C in the first phase, and it formed with gas pressure applied at a global temperature increasing from 400°C to 500°C. Because of the non-isothermal heating of material, it was found that it had enough ductility to flow more easily in the specific zones (die corners and radius). Additionally, FEM results showed that a better formed part can be obtained by the increasing temperature forming, compared to the stable temperature phase. © 2010 American Institute of Physics.

  • 103.
    Liu, J.
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Tan, M. -J
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Jarfors, A. -E.-W.
    Singapore Institute of Manufacturing Technology.
    Aue-u-lan, Y.
    Singapore Institute of Manufacturing Technology.
    Castagne, S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Formability in AA5083 and AA6061 alloys for light weight applications2010Inngår i: Materials & Design, ISSN 0261-3069, Vol. 31, nr SUPPL. 1, s. S66-S70Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With recent development in the automotive and aerospace industries, the lightweight, yet inexpensive aluminum alloys are of great demand in industrial applications. In this paper, considering the limited applications in non-superplastic materials, two typical alloys of AA5083 and AA6061 were investigated and compared during high temperature tensile tests to study their formability. The results of tensile tests and microstructures were shown, which indicated the deformation properties under different conditions. Both alloys exhibited relatively weak strain hardening effects especially at relatively lower strain rates. Furthermore, the highest strain rate sensitivity index (m value) was obtained, and the peak of percent elongation-to-failure also coincided with the ranges of highest m value. The flow stress coupled with the dynamic grain growth was related with the temperatures and strain rates. The grains appeared to be coarser in the deformed samples. Cavitation and recrystallization have also been found as a result of strain rate and temperature. © 2009 Elsevier Ltd.

  • 104.
    Malakizadi, Amir
    et al.
    Chalmers Institute of Technology, Gothenburg, Sweden.
    Ghasemi, Rohollah
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Behring, Carsten
    Chalmers Institute of Technology, Gothenburg, Sweden.
    Olofsson, Jakob
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Nyborg, Lars
    Chalmers Institute of Technology, Gothenburg, Sweden.
    Machinability of solid solution-strengthened compacted graphite iron: Influence of the microstructure, mechanical properties and cutting conditions on tool wear responseManuskript (preprint) (Annet vitenskapelig)
  • 105.
    Malakizadi, Amir
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Ghasemi, Rohollah
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Behring, Carsten
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Olofsson, Jakob
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Nyborg, Lars
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Krajnik, Peter
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron2018Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 410-411, s. 190-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.

  • 106.
    Maryam, Eslami
    et al.
    University of Trento, Italy.
    Payandeh, Mostafa
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Deflorian, Flavio
    University of Trento, Italy.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Zanella, Caterina
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys2018Inngår i: Metals, Vol. 8, nr 4, artikkel-id 209Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrosion properties of two Al–Si alloys processed by Rheo-high pressure die cast (HPDC) method were examined using polarization and electrochemical impedance spectroscopy (EIS) techniques on as-cast and ground surfaces. The effects of the silicon content, transverse and longitudinal macrosegregation on the corrosion resistance of the alloys were determined. Microstructural studies revealed that samples from different positions contain different fractions of solid and liquid parts of the initial slurry. Electrochemical behavior of as-cast, ground surface, and bulk material was shown to be different due to the presence of a segregated skin layer and surface quality.

  • 107.
    Matsushita, Taishi
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Saro, Albano Gómez
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Elmquist, Lennart
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    On Thermal Expansion and Density of CGI and SGI Cast Irons2015Inngår i: Metals, ISSN 2075-4701, Vol. 5, nr 2, s. 1000-1019, artikkel-id met5021000Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal expansion and density of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured in the temperature range of 25–500 °C using push-rod type dilatometer. The coefficient of the thermal expansion (CTE) of cast iron can be expressed by the following equation: CTE = 1.38 × 10−5 + 5.38 × 10−8 N − 5.85 × 10−7 G + 1.85 × 10−8 T − 2.41 × 10−6 RP/F − 1.28 × 10−8 NG − 2.97 × 10−7 GRP/F + 4.65 × 10−9 TRP/F + 1.08 × 10−7 G2 − 4.80 × 10−11 T2 (N: Nodularity, G: Area fraction of graphite (%), T: Temperature (°C), RP/F: Pearlite/Ferrite ratio in the matrix).

  • 108.
    Matsushita, Taishi
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Saro, Albano Gómez
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Elmquist, Lennart
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    On the specific heat and thermal diffusivity of CGI and SGI cast irons2017Inngår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 30, nr 5, s. 276-282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The specific heat and thermal diffusivity of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured at temperatures ranging between 373 and 773 K (100 and 500 °C) using differential scanning calorimetry (DSC) and between 298 and 773 K (25 and 500 °C) using the laser flash method, respectively. Specific heat increased with increasing amounts of graphite and pearlite, as well as with Si content. As a recommended value of the specific heat for fully ferritic high-silicon SGI, the following relation was suggested:(Formula presented.) where T is the temperature in Celsius, (Formula presented.) is the mass% of Si, and fg is the area fraction of graphite (%). The thermal diffusivity of cast irons tends to increase with increasing amounts of graphite, and decrease with greater nodularity. It was found that nodularity had a strong influence on thermal diffusivity in the nodularity range of 15–30%. 

  • 109.
    Matsushita, Taishi
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Saro, Albano Gómez
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Elmquist, Lennart
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    On the thermal conductivity of CGI and SGI cast irons2018Inngår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 31, nr 3, s. 135-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal conductivity of Compacted Graphite Iron (CGI) and spheroidal graphite iron (SGI) was established in the temperature range from room temperature up to 500 °C using the experimental thermal diffusivity, density and specific heat values. The influence of nodularity, graphite amount, silicon content and temperature on the thermal conductivity of fully ferritic high-silicon cast irons was investigated. It was found that the CGI materials showed higher thermal conductivity than the SGI materials. The thermal conductivity tended to increase with increasing temperature until it reached a maximum followed by a subsequent decrease as temperature was increased up to 500 °C. Conventional models were applied to estimate thermal conductivity and the predictive accuracy of each model was evaluated. The thermal conductivity could be estimated by the Helsing model. The Maxwell model, Bruggeman model and Hashin–Shtrikman model were also in fair agreement using the thermal conductivity value of graphite parallel to the basal planes in graphite. 

  • 110.
    Ng, B. S.
    et al.
    Sch. of Mech. and Prod. Engineering, Division of Materials Engineering, Nanyang Technol. Univ., 50 N., Singapore.
    Annergren, I.
    Singapore Inst. of Mfg. Technology.
    Soutar, A. M.
    Singapore Inst. of Mfg. Technology.
    Khor, K. A.
    Sch. of Mech. and Prod. Engineering, Division of Materials Engineering, Nanyang Technol. Univ., 50 N., Singapore.
    Jarfors, A. E. W.
    Singapore Inst. of Mfg. Technology.
    Characterisation of a duplex TiO2/CaP coating on Ti6Al4V for hard tissue replacement2005Inngår i: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 26, nr 10, s. 1087-1095Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An initial TiO2 coating was applied on Ti6Al4V by electrochemical anodisation in two dissimilar electrolytes. The secondary calcium phosphate (CaP) coating was subsequently applied by immersing the substrates in a simulated body fluid (SBF) with three times concentration (SBF×3), mimicking biomineralisation of biological bone. Electrochemical impedance spectroscopy and potentiodynamic polarisation assessments in SBF revealed that the anodic TiO2 layer is compact, exhibiting up to four-folds improvement in in vitro corrosion resistance over unanodised Ti6Al4V. X-ray photoelectron spectroscopy analysis indicates that the anodic Ti oxide is thicker than air-formed ones with a mixture of TiO2-x compound between the TiO2/Ti interfaces. The morphology of the dense CaP film formed, when observed using scanning electron microscopy, is made up of linked globules 0.1-0.5ÎŒm in diameter without observable delamination. Fourier transform infrared spectrometry with an attenuated total internal reflection analysis revealed that this film is an amorphous/poorly crystallised calcium-deficient-carbonated CaP system. The calculated Ca:P ratios of all samples (1.14-1.28) are lower than stoichiometric hydroxyapatite (1.67). These results show that a duplex coating consisting of (1) a compact TiO2 with enhanced in vitro corrosion resistance and (2) bone-like apatite coating can be applied on Ti6Al4V by anodisation and subsequent immersion in SBF. © 2004 Elsevier Ltd. All rights reserved.

  • 111.
    Ng, G. K. L.
    et al.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Jarfors, A. E. W.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Bi, G.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Zheng, H. Y.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Porosity formation and gas bubble retention in laser metal deposition2009Inngår i: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 97, nr 3, s. 641-649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. The study shows that the gas porosity is dependent on the process parameters and the melt pool dynamics. The flotation of entrapped gas bubbles was analysed, showing that in a stationary melt pool the gas would be retained by Marangoni-driven flow. The overall Marangoni-driven flow of the melt pool is in the order of five times higher than the flotation effect, and this is the reason why the melt pool geometry would tend to dominate the flow direction of the gas bubbles. Through optimisation, the gas porosity can be reduced to 0.037%. © 2009 Springer-Verlag.

  • 112.
    Pang, J. J.
    et al.
    Sch. of Mech. and Aerospace Eng., Nanyang Technological University, Singapore.
    Tan, M. J.
    Sch. of Mech. and Aerospace Eng., Nanyang Technological University, Singapore.
    Jarfors, A.
    Singapore Institute of Manufacturing Technology.
    Chuang, P. D.
    Miracle Machines Pte. Ltd., Singapore.
    Glass formation and structural study of Ti50Cu50 alloy by molecular dynamics2010Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 638-642, s. 1665-1670Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ti-based metallic glasses (MGs) due to their relative low densities exhibit ultrahigh specific characteristics. In this article the glass-forming behavior and atomic structure of Ti50Cu50 MG were investigated through molecular dynamics simulation (MDS) using the general embedded-atom method (GEAM) potential. As observed experimentally, simulated Ti 50Cu50 alloy undergoes three states on quenching: (i) equilibrium liquid; (ii) supercooled liquid and (iii) glassy solid. The atomic configuration of the glass was analysed based on the radial distribution function (RDF) and Voronoi tessellation (VT). It was found that there exist a variety of polyhedral units in Ti50Cu50 MG, where distorted icosohedral and bcc clusters are dominant. © (2010) Trans Tech Publications.

  • 113.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Belov, Ilja
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Jarfors, Anders E.W
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. RheoMetal.
    Effect of Material Inhomogeneity on Thermal Performance of a Rheocast Aluminum Heatsink for Electronics Cooling2016Inngår i: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 25, nr 6, s. 2116-2127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relation between microstructural inhomogeneity and thermal conductivity of a rheocast componentmanufactured from two different aluminum alloys was investigated. The formation of two different primarya-Al particles was observed and related to multistage solidification process during slurry preparationand die cavity filling process. The microstructural inhomogeneity of the component was quantified as thefraction of a1-Al particles in the primary Al phase. A high fraction of coarse solute-lean a1-Al particles inthe primary Al phase caused a higher thermal conductivity of the component in the near-to-gate region. Avariation in thermal conductivity through the rheocast component of 10% was discovered. The effect of aninhomogeneous temperature-dependent thermal conductivity on the thermal performance of a largerheocast heatsink for electronics cooling in an operation environment was studied by means of simulation.Design guidelines were developed to account for the thermal performance of heatsinks with inhomogeneousthermal conductivity, as caused by the rheocasting process. Under the modeling assumptions, the simulationresults showed over 2.5% improvement in heatsink thermal resistance when the higher conductivity nearto-gate region was located at the top of the heatsink. Assuming homogeneous thermo-physical properties ina rheocast heatsink may lead to greater than 3.5% error in the estimation of maximum thermal resistanceof the heatsink. The variation in thermal conductivity within a large rheocast heatsink was found to beimportant for obtaining of a robust component design.

  • 114.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Solidification sequence and evolution of microstructure during rheocasting of four Al-Si-Mg-Fe alloys with Low Si content2016Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47, nr 3, s. 1215-1228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four Al-Si-Mg-Fe alloys with Si contents varying from 1.6 to 4.5 wt pct were rheocast, using the RheoMetal™ process to prepare slurry and cast in a vertical high-pressure die casting machine. Particle size and Si concentration in the α-Al particles in the slurry and in the as-rheocast component were investigated. A uniform distribution of Si in the globular α 1-Al particles was achieved in the slurry. In the rheocast samples, measurement of the α 1-Al particles showed that these particles did not increase significantly in size during pouring and secondary solidification. The two additional α-Al particles types, α 2-Al particles and α 3-Al particles, were identified as being a result of two discrete nucleation events taking place after slurry production. The Si concentration in the α 2-Al and α 3-Al particles indicated that the larger α 2-Al particles precipitated before the α 3-Al particles. In addition, in the as-rheocast condition, the Si distribution inside the α 1-Al particles showed three distinct zones; an unaffected zone, a transition zone, and in some cases the start of a dendritic/cellular zone. The phenomenon of dendritic growth of globular α 1-Al particles during secondary solidification occurred concomitantly with the final eutectic reaction and increased with increasing amount of the Al-Si eutectic phase.

  • 115.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. RheoMetal.
    The effect of microstructural inhomogeneity on thermal diffusivity in a rheocast component2016Inngår i: La Metallurgia Italiana, ISSN 0026-0843, Vol. 108, nr 6, s. 57-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between microstructural characteristics and thermal diffusivity of a rheocast component was investigated for two Al-Si-Mg-Fe alloys with low Si contents. The microstructural investigation of the components clearly depicted the formation of coarse solute-lean globular α1-Al particles during the slurry fabrication process and fine solute-rich α2-Al and α3-Al particles during the secondary solidification in the die cavity. The microstructural characterization was quantified based on the amount of α1-Al particles in different locations of the component. The result clearly revealed a presence of both longitudinal and transverse macrosegregation of solute-lean α1-Al particles in the rheocast component. The study of thermal diffusivity and hardness revealed that the regions of the component with a high fraction of α1-Al particles had a higher thermal diffusivity but a lower hardness. Silicon in the solid solution was observed to be a critical factor in reducing the thermal diffusivity. The comparison between the effect of longitudinal and transverse segregation on thermal diffusivity showed that the transverse segregation had a stronger impact.

  • 116.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessen, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Effect of superheat on melting rate of EEM of Al alloys during stirring using the RheoMetal process2013Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 192-193, s. 392-397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The RheoMetal process (previously called the Rapid S- and RSF- process) is a novelmethod to produce cost effective, high quality, semisolid slurries for component casting. TheRheoMetal process uses an Enthalpy Exchange Material (EEM) as cooling agent to absorb heat andproduce a slurry. Critical process parameters to create a slurry by robust melting of the EEM arealloy content, stirring speed, EEM to melt ratio, EEM temperature, EEM microstructuralcharacteristics and melt superheat.In this paper, the melting sequence and melting rate of the EEM was studied experimentally. Theeffect of EEM composition, as well as superheat, on evolution of shape and dimension of the EEMduring stirring was investigated. Initial material freezing onto the EEM was observed, followed by astationary phase with subsequent gradual melting of the EEM. It was shown that the characteristicsof freeze-on layer were strongly correlated to melt superheat, EEM temperature, as well as materialcomposition, hence also has significant influence on the melting sequence.

  • 117.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content2015Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 217-218, s. 67-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the current paper, a low-Si aluminium alloy (1.4-2.4% Si) was used to fabricate acomplex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC),process. Microstructure and fracture characteristics were investigated. The cast material exhibitedmicrostructural inhomogeneity, in particular macrosegregation in the form of liquid surfacesegregation bands in addition to sub-surface pore bands and gross centre porosity. Tensilespecimens were taken from the cast components. Elongation and microstructural inhomogeneitywere investigated and correlated. Fracture surfaces of the tensile specimen were examined underscanning electron microscope (SEM). The study showed that both near surface liquid segregationbands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss ofductility was gross centre porosity. The centre porosity was found to be a combination of trappedgas and insufficient, irregular feeding patterns.

  • 118.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Sabzevar, Mohsen H.
    Department of Materials Engineering Ferdowsi University of Mashhad, Mashhad, Iran.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Solidification and re-melting phenomena during the slurry preparation stage using the RheoMetalTM process2016Rapport (Annet vitenskapelig)
    Abstract [en]

    The melting sequence of the Enthalpy Exchange Material (EEM) and formation of slurry in the RheoMetalTM process was investigated. The EEM was extracted, together with a portion of the slurry at different times before complete melting, and quenched. The EEM initially increased in size due to melt freezing onto its surface, forming a freeze-on layer. The initial growth of this layer was followed by a constant diameter of the EEM and thereafter subsequent melting. Microstructural characterization of the size and morphology of different phases in the EEM and the freeze-on layer was made. Dendritic equiaxed grains and eutectic regions containing Si particles and Cu-bearing particles were observed in the as-cast EEM. The freeze-on layer consisted of dendritic aluminum slightly tilted by about 30° toward the upstream direction, caused by the rotation of the EEM. Energy Dispersion Spectroscopy analysis showed that the freeze-on layer had a composition corresponding to a higher melting point than the EEM.

    Microstructural investigation of the EEM showed that the temperature rapidly increased to 495 ºC, causing incipient melting of Al2Cu and Al5Mg8Si6Cu2 phases in grain boundary regions. Following the incipient melting, the temperature in the EEM increased further and binary Al-Si eutectic started to melt to form a region of a fully developed coherent mushy state. Experimental results and a thermal model indicated that as the dendrites spheroidized and the interface at the EEM/freeze-on layer reached a mushy state with 25% solid fraction, coherency was lost and disintegration of the freeze-on layer took place. Subsequently, in the absence of the shielding effect from the freeze-on Layer, the EEM disintegrates at a higher solid fraction, estimated to be 50%. The fast and complex slurry generation in the RheoMetalTM process is a hybrid process with both rheocasting and thixocasting elements in the process.

  • 119.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Sabzevar, Mohsen Haddad
    Department of Metallurgical and Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Solidification and re-melting phenomena during slurry preparation using the RheoMetal™ process2017Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The melting sequence of the enthalpy exchange material (EEM) and formation of a slurry in the RheoMetal™ process was investigated. The EEM was extracted and quenched, together with a portion of the slurry at different processing times before complete melting. The EEM initially increased in size/diameter due to melt freezing onto its surface, forming a freeze-on layer. The initial growth of this layer was followed by a period of a constant diameter of the EEM with subsequent melting and decrease of diameter. Microstructural characterization of the size and morphology of different phases in the EEM and in the freeze-on layer was made. Dendritic equiaxed grains and eutectic regions containing Si particles and Cu-bearing particles and Fe-rich particles were observed in the as-cast EEM. The freeze-on layer consisted of dendritic aluminum tilted by about 30 deg in the upstream direction, caused by the rotation of the EEM. Energy dispersion spectroscopy analysis showed that the freeze-on layer had a composition corresponding to an alloy with higher melting point than the EEM and thus shielding the EEM from the surrounding melt. Microstructural changes in the EEM showed that temperature rapidly increased to 768 K (495 °C), indicated by incipient melting of the lowest temperature melting eutectic in triple junction grain boundary regions with Al2Cu and Al5Mg8Si6Cu2 phases present. As the EEM temperature increased further the binary Al-Si eutectic started to melt to form a region of a fully developed coherent mushy state. Experimental results and a thermal model indicated that as the dendrites spheroidized near to the interface at the EEM/freeze-on layer reached a mushy state with 25 pct solid fraction, coherency was lost and disintegration of the freeze-on layer took place. Subsequently, in the absence of the shielding effect from the freeze-on Layer, the EEM continued to disintegrate with a coherency limit of a solid fraction estimated to be 50 pct.

  • 120.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Sjölander, Emma
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E.W
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessen, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Mechanical And Thermal Properties Of Rheocast Telecom Component Using Low Silicon Aluminium Alloy In As-Cast And Heat-Treated Conditions2015Inngår i: Light Metals 2015 / [ed] Margaret Hyland, Hoboken, NJ: John Wiley & Sons, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The growing demand for increasingly more cost and energy effective electronics components is a challenge for the manufacturing industry. To achieve higher thermal conductivity in telecom components, an aluminum alloy with a composition of Al-2Si-0.8Cu-0.8Fe-0.3Mn was created for rheocasting. Yield strength and thermal conductivity of the material were investigated in the as cast, T5 and T6 heat-treated conditions. The results showed that in the as-cast condition thermal conductivity of 168 W/mK and yield strength of 67 MPa was achieved at room temperature. A T5 treatment at 200°C and 250°C increased thermal conductivity to 174 W/mK and 182 W/mK, respectively, while only a slight increase in yield strength was observed. Moreover, a T6 treatment resulted in similar thermal conductivity as the T5 treatment at 250°C with no significant improvement in yield strength. Therefore, the T5 treatment at 250°C was suggested as an optimum condition for the current alloy composition.

  • 121.
    Payandeh, Mostafa
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Sjölander, Emma
    Scania CV AB, Materials Technology, Södertälje, Sweden.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Influence of microstructure and heat treatment on thermal conductivity of rheocast and liquid die cast Al-6Si-2Cu-Zn alloy2016Inngår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, nr 4, s. 202-213Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal conductivity of a rheocast component made from Stenal Rheo1 (Al-6Si-2Cu-Zn) alloy was investigated in as-cast, T5 and T6 conditions. The thermal conductivity measurement in different locations showed variation of this property throughout the rheocast component. The results of microstructural investigation revealed that the ratio of solute-lean α1-Al particles formed during slurry preparation to fine solute-rich α2-Al particles formed during secondary solidification had significant influence on thermal conductivity. The reduced amount of solutes in the α1-Al particles was determined as the root cause of higher thermal conductivity. A linear relation between the fraction of precipitates and the increase in thermal conductivity was obtained and silicon in solid solution is shown to have a dominant influence. As silicon was precipitated during the heat treatment, thermal conductivity increased. For an optimal combination of thermal and mechanical properties, it is therefore important to use an ageing temperature above the temperature of Si precipitation.

  • 122.
    Persson, P.
    et al.
    Swedish Defence Materials Administration, Stockholm, Sweden.
    Jarfors, A. E. W.
    Department of Materials Processing, Royal Institute of Technology, Stockholm, Sweden.
    Savage, S.
    Swedish Defence Research Establishment, Stockholm, Sweden.
    Self-propagating high-temperature synthesis and liquid-phase sintering of TiC/Fe composites2002Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 127, nr 2, s. 131-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present paper addresses a possible route for the manufacturing of iron-based metal-matrix composites (MMCs) with a high level of reinforcement. The ceramic reinforcement studied was titanium carbide (TiC). TiC is one of the hardest materials to be found, which is why a TiC/Fe composite has the potential to be used as armour. Two manufacturing routes have been evaluated experimentally, i.e., liquid-phase sintering (LPS) and self-propagating high-temperature synthesis (SHS). LPS was found to be more effective due to easier process control and due to the process yielding a more homogeneous material. Both LPS and SHS produced a material with a relatively high degree of porosity. The porosity in the LPS experiments could be decreased by varying the process parameters, but this was not possible in the SHS process. Metallographic investigation shows that the TiC/Fe system is feasible and that applications utilising TiC/Fe composites are possible in the future. This is due to the fact that despite the porosity, an improvement of the MMC properties is detected, compared to those of the matrix material. © 2002 Elsevier Science B.V. All rights reserved.

  • 123.
    Rastegari, H.
    et al.
    Department of Engineering, Birjand University of Technology.
    Kermanpur, A.
    Department of Materials Engineering, Isfahan University of Technology.
    Najafizadeh, A.
    Fould Institute of Technology.
    Somani, M.C.
    Centre for Advanced Steels Research, University of Oulu.
    Porter, D.A.
    Centre for Advanced Steels Research, University of Oulu.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Determination of processing maps for the warm working of vanadium microalloyed eutectoid steels2016Inngår i: Materials Science and Engineering: A, ISSN 0921-5093, Vol. 658, s. 167-175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microalloying of an eutectoid steel with V may facilitate formation of dispersed nano-scaled VC particles in the microstructure during thermomechanical processing or subsequent heat treatment. In this research, the constitutive flow behavior of vanadium microalloyed eutectoid steel has been investigated in the temperature range 620–770 °C at strain rates in the range 0.01–10 s−1. Microstructural characterization of the deformed specimens was conducted using SEM and EBSD techniques. In this context, various deformation mechanisms occurring during warm deformation have been characterized and delineated through construction of a processing map by establishing a power dissipation map and an instability map for the steel and superimposing them. The results show that the pearlitic microstructure exhibits several deformation mechanisms within these warm working conditions. Dynamic spheroidization of cementite lamella takes place in the range 660–720 °C and 0.01–0.1 s−1 with a power dissipation efficiency of 27–33%, characterizing a safe window of processing this steel. The presence of vanadium carbides at grain boundaries strengthened the pearlitic microstructure and retarded the occurrence of some deformation defects during low temperature, high speed deformation in the range 620–720 °C and 1–10 s−1.

  • 124.
    Raza, Mohsin
    et al.
    School of Innovation, Design and Engineering, Mälardalen University, Eskilstuna, Sweden.
    Silva, P.
    TPC Components AB, Hallstahammar, Sweden.
    Irwin, Mark
    TPC Components AB, Hallstahammar, Sweden.
    Fagerström, Björn
    School of Innovation, Design and Engineering, Mälardalen University, Eskilstuna, Sweden.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Effects of process related variations on defect formation in investment cast components2018Inngår i: Archives of Foundry Engineering, ISSN 1897-3310, E-ISSN 2299-2944, Vol. 18, nr 1, s. 103-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly. 

  • 125.
    Raza, Mohsin
    et al.
    School of Innovation, Design and Engineering, Mälardalen University, Eskilstuna, Sweden.
    Svenningsson, Roger
    Swerea SWECAST AB, Jönköping, Sweden.
    Irwin, Mark
    TPC Components AB, Hallstahammar, Sweden.
    Fägerström, Björn
    School of Innovation, Design and Engineering, Mälardalen University, Eskilstuna, Sweden.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Effects of process related variations on fillablity simulation of thin-walled IN718 structures2018Inngår i: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193, Vol. 12, nr 3, s. 543-553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulation tools have improved significantly and are now capable of accurately predicting mould filling behavior. The quality of prediction is highly dependent on material properties and set-up of boundary conditions for the simulation. In this work material properties were measured and casting conditions were analyzed to accurately replicate the casting process in simulation. The sensitivity of the predictions to minor process variations commonly found in foundries was evaluated by comparing simulation and cast samples. The observed discrepancies between simulation and cast samples were evaluated and discussed in terms of their dependency on process variations. It was concluded that the simulation set-up was capable of reasonable predictions and could replicate the asymmetry of the filling however did not accurately predict the absolute value of the unfilled area. It was discovered that asymmetric flow due to variations in the orientation of the casting mould during filling could have greater influence on the predictions than the actual variation in fill time. The quality of simulation is dependent on equipment and techniques used in the foundry as well as the metallurgical model to simulate the process. 

  • 126.
    Salomonsson, Kent
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Three-dimensional microstructural characterization of cast iron alloys for numerical analyses2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, s. 427-435Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we aim at characterizing three different cast iron alloys and their microstructural features, namely lamellar, compacted and nodular graphite iron. The characterization of microscopic features is essential for the development of methods to optimize the behavior of cast iron alloys; e.g. maximize thermal dissipation and/or maximize ductility while maintaining strength. The variation of these properties is commonly analyzed by metallography on two-dimensional representations of the alloy. However, more precise estimates of the morphologies and material characteristics are obtained by three-dimensional reconstruction of microstructures. The use of X-ray microtomography provides an excellent tool to generate high resolution threedimensional microstructure images. The characteristics of the graphite constituent in the microstructure, including the size, shape and connectivity, were analyzed for the different cast iron alloys. It was observed that the lamellar and compacted graphite iron alloys have relatively large connected graphite morphologies, as opposed to ductile iron where the graphite is present as nodules. The results of the characterization for the different alloys were ultimately used to generate finite element models.

  • 127.
    Santos, Jorge
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Filling, Feeding and Defect Formation of Thick-Walled AlSi7Mg0.3 Semi-Solid Castings2016Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 256, s. 222-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aluminium semi-solid castings have gained increased attention due to their superior mechanical properties, lower porosity compared to conventional high pressure die cast material. These characteristics suggests that semi-solid casting should be suitable to produce thick-walled structural components, yet most successful applications of semisolid casting have been for thin-walled components. There is a lack of understanding on filling and feeding related defect formation for semi-solid castings with thick-walled cross-sections. In the current study an AlSi7Mg0.3 aluminium alloy was used to produce semi-solid castings with a wall thickness of 10mm using a Vertical High Pressure Die Casting machine. The RheoMetalTM process was used for slurry preparation. The primary solid α-Al fraction in the slurry was varied together with die temperature. The evaluation of the filling related events was made through interrupted shots, stopping the plunger at different positions. Microscopy of full castings and interrupted test samples were performed identifying the presence of surface segregation layer, shear bands, gas entrapment, shrinkage porosity as well as burst feeding.

  • 128.
    Santos, Jorge
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Formation of Iron-Rich Intermetallic Phases in Al-7Si-Mg: Influence of Cooling Rate and Strontium Modification2019Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 50, nr 9, s. 4148-4165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of cooling rate on the formation of iron-rich intermetallic phases during solidification of unmodified and strontium-modified Al-7Si-0.3Mg alloys has been investigated. The effect of strontium on the intermetallic phases was evaluated in unquenched and quenched samples. Samples were quenched before the start of the Al-Si eutectic reaction, along the Al-Si eutectic reaction and just after the end of solidification. The results show that the addition of strontium increased the size of both β-Al5FeSi and π-Al8FeMg3Si6 at low cooling rates. For unmodified and strontium-modified alloys, an increase of cooling rate resulted in a decrease in size of the intermetallic phases, particularly in the strontium modified alloy. In the strontium modified alloy quenched before the start of the Al-Si eutectic reaction, π-Al8FeMg3Si6 appeared as thin platelets at the eutectic cell boundaries. Chinese script-like π-Al8FeMg3Si6 and platelet-like β-Al5FeSi intermetallic phases were observed uniformly distributed in the eutectic regions in the unmodified alloy quenched before the start of the eutectic reaction. Strontium modified semi-solid Al-7Si-0.3Mg castings were produced and the type of intermetallic phase, morphology, size, area fraction and distribution were similar to that observed in the strontium modified alloy quenched before the start of the Al-Si eutectic reaction.

  • 129.
    Santos, Jorge
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    The effect of magnesium on the intermetallic phases and heat treatment response of cast Al‐7Si‐MgManuskript (preprint) (Annet vitenskapelig)
  • 130.
    Santos, Jorge
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Variation of properties in the cross-section of semi-solid al-7si-0.3mg castings2019Inngår i: Semi-Solid of Alloys and Composites / [ed] Rassili A.,Midson S.P.,Zhu Q.,Gang Hu X., Trans Tech Publications, 2019, s. 81-86Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In semi-solid casting, a slurry consisting of primary α-Al crystals and liquid is injected into the die cavity. The solidification in the die-cavity occurs by the growth of the primary α-Al crystals formed during slurry preparation and in the shot sleeve, nucleation and growth of in-cavity solidified crystals and ends with the eutectic reaction. During solidification in the die cavity, the cooling rate near the die wall is higher in comparison to the centre of the casting, particularly for thick-walled castings. The solidification conditions for the slurry α-Al crystals that are closer to the die wall can be very different compared to the slurry α-Al crystals located at the casting centre. This can result in different solute concentration in the interior of the α-Al globules in different regions of the semi-solid casting cross-section and consequently, different response to heat treatament. The RheoMetal™ process was used to produce thick-walled semi-solid castings. Semi-solid castings in the as-cast and T6 conditions were investigated. Indentation tests for hardness measurements in the nano-range were performed in the interior of α-Al globules near the surface and at the casting cross-section centre. The hardness variation across the casting cross-section was evaluated by low-force Vickers hardness. The castings in the as-cast condition showed more uniform properties in the cross-section compared to the T6 condition. Additionally, the results suggest that microsegregation in the interior of α-Al globules is very low in castings in the as-cast and T6 conditions. 

  • 131.
    Santos, Jorge
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Kallien, Lothar H.
    Department of Applied Sciences, Aalen University, Aalen, Germany.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Influence of grain refinement on slurry formation and surface segregation in semi-solid Al-7Si-0.3Mg castings2018Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, nr 10, s. 4871-4883Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to evaluate the effect of grain refinement on slurry formation and surface segregation in semi-solid castings produced by the Rheometal™ process. The effect of two grain refiners, Al-8B and Al-5Ti-1B, on the slurry α-Al grain size, shape factor and solid fraction was evaluated. The results suggest that the addition of a grain refiner can affect the solid fraction obtained in the RheometalTM process and, consequently, reduce the solute content near the casting surface. Grain refiner addition resulted in a larger fraction of α-Al grains ≤ 60 µm for the refined alloys compared with the unrefined alloy. Additionally, the growth of α-Al slurry globules was greater for the unrefined alloy compared with the refined alloy during solidification in the die-cavity. A more homogeneous and finer microstructure was observed near the surface in the grain-refined castings compared with the unrefined castings. Evidence of significant liquid penetration was identified in some α-Al globules, indicating that disintegration of α-Al globules may occur during the Rheometal™ casting process.

  • 132.
    Seifeddine, Salem
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Zetterlind, Madelene
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell organisation och produktion.
    Keller, Christina
    Högskolan i Jönköping, Internationella Handelshögskolan, IHH, Informatik.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Development of an online learning master program with specialization in cast metals engineering: Challenges and opportunities2015Konferansepaper (Fagfellevurdert)
  • 133.
    Shanthi, M.
    et al.
    Sch. of Mech. and Aerospace Eng., Nanyang Technological University, Singapore.
    Gupta, M.
    Dept. of Mechanical Engineering, National University of Singapore.
    Jarfors, A. E. W.
    Sch. of Mech. and Aerospace Eng., Nanyang Technological University, Singapore.
    Tan, M. J.
    Sch. of Mech. and Aerospace Eng., Nanyang Technological University, Singapore.
    Producing magnesium metallic glass by disintegrated melt deposition2010Inngår i: AIP Conference Proceedings, Paris, 2010, Vol. 1315, s. 781-786Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their low density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties. © 2010 American Institute of Physics.

  • 134.
    Shanthi, M.
    et al.
    Sch. of Mech. & Aerospace Eng., Nanyang Technological University, Singapore.
    Gupta, M.
    Department of Mechanical Engineering, National University of Singapore.
    Jarfors, A. E. W.
    Sch. of Mech. & Aerospace Eng., Nanyang Technological University, Singapore.
    Tan, M. J.
    Sch. of Mech. & Aerospace Eng., Nanyang Technological University, Singapore.
    Synthesis, characterization and mechanical properties of nano alumina particulate reinforced magnesium based bulk metallic glass composites2011Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 528, nr 18, s. 6045-6050Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mg67Zn28Ca5 bulk metallic glass reinforced with 0.66-1.5vol% of nano alumina particulates were successfully synthesized using disintegrated melt deposition technique. Microstructural characterization revealed reasonably uniform distribution of alumina particulates in a metallic glass matrix. The reinforced particles have no significant effect on the glass forming ability of the monolithic glass matrix. Mechanical characterization under compressive loading showed improved micro hardness, fracture strength and failure strain with increase in nano alumina particulate reinforcement. The best combination of strength, hardness and ductility was observed in Mg/1.5vol% alumina composite with fracture strength of 780MPa and 2.6% failure strain.

  • 135.
    Siafakas, Dimitrios
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Matsushita, Taishi
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Hakamada, Shinya
    Gakushuin Univ, Dept Phys, Tokyo, Japan.
    Onodera, Kenta
    Gakushuin Univ, Dept Phys, Tokyo, Japan.
    Kargl, Florian
    German Aerosp Ctr DLR, Inst Mat Phys Space, Cologne, Germany.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Watanabe, Masahito
    Gakushuin Univ, Dept Phys, Tokyo, Japan.
    Measurement of Viscosity of SiO2-CaO-Al2O3 Slag in Wide Temperature Range by Aerodynamic Levitation and Rotating Bob Methods and Sources of Systematic Error2018Inngår i: International journal of microgravity science and application, ISSN 0915-3616, Vol. 35, nr 2, artikkel-id 350204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Viscosity measurements for SiO2-CaO-Al2O3 based ternary slags with low SiO2 content were performed for a wide temperature range utilizing the aerodynamic levitation and rotating bob methods. Aerodynamic levitation was used for temperatures >= 2229 K and the viscosity was calculated by the sample oscillation decay time. The rotating bob method was used for temperatures <= 1898 K and the viscosity was determined by the variation of the torque at different rotation speeds. Fitting curves were created using Mauro’s viscosity equation. The main sources of systematic error were identified to be the sample weight measurement, the resolution of the high-speed camera, the fitting of the linear trend line in the torque against rpm diagrams and the vertical position of the bob. The combined standard uncertainty from all error sources was calculated for both measurement methods.

  • 136.
    Siafakas, Dimitrios
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Matsushita, Taishi
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Hakamada, Shinya
    Department of Physics, Gakushuin University, Tokyo, Japan.
    Watanabe, Masahito
    Department of Physics, Gakushuin University, Tokyo, Japan.
    Viscosity of SiO2–CaO–Al2O3 slag with low silica – Influence of CaO/Al2O3, SiO2/Al2O3 ratio2018Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 12, s. 2180-2185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The viscosity of low SiO2 (10–20 mass%)-CaO-Al2O3 slag system was measured in a wide temperature range (1 623–2 800 K) using the rotational bob method and the aerodynamic levitation method. The influence of SiO2/Al2O3 ratio and CaO/Al2O3 ratio on the viscosity was examined. It was concluded that the SiO2/Al2O3 ratio did not affect the degree of polymerization of the aluminosilicate network in the composition range of the present study. An abnormal behaviour of the viscosity was observed at a CaO/Al2O3 ratio of 1.57 which was attributed to the formation of 12CaO·7Al2O3-like clusters. It was concluded that the overall influence on the viscosity could be expressed as the summation of the influence from the aluminosilicate network and the influence from the cluster formation of the primary precipitating solid phase. The temperature dependence of the cluster formation was coupled to the driving force of precipitation of the 12CaO·7Al2O3 phase.

  • 137.
    Siafakas, Dimitrios
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Matsushita, Taishi
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Lauenstein, Åsa
    Swerea SWECAST AB.
    Ekerot, Sven
    Comdicast AB.
    Particles precipitation in Ti and Al deoxidized Hadfield steels2016Inngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, nr 10, s. 1344-1355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The characteristics and precipitation mechanism of particles in titanium and aluminum treated Hadfield steel casted during pilot scale experiments have been studied. Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were utilized for the particle analysis and characterization. Additionally, thermodynamic equilibrium calculations were performed using Thermo-Calc software. Aluminum oxides, titanium carbon nitrides, titanium carbides and manganese sulfides were the main types of particles found. The order of precipitation during solidification and chemical composition range of each type of particle was determined. Aluminum Oxides were found to act as nucleation sites fortitanium carbon nitrides. Thermodynamic equilibrium calculation for particles characteristics were in good agreement with the experimental findings. Titanium carbides were found to form during initial stages of the Ferro-titanium additions dissolution.

  • 138.
    Siafakas, Dimitrios
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Matsushita, Taishi
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Lauenstein, Åsa
    Swerea SWECAST AB, Sweden.
    Ekerot, Sven
    Comdicast AB, Sweden.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    A particle population analysis in Ti- and Al-deoxidized Hadfield steels2018Inngår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 31, nr 3, s. 125-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A quantitative analysis of the amount, size and number of particles that precipitate in situ in titanium- and aluminium-treated Hadfield steel cast during pilot-scale experiments has been performed. SEM with EDS and automated particle analysis abilities was utilized for the analysis. Additionally, Thermo-Calc was used for thermodynamic calculations and Magma 5 for solidification and cooling simulations. Predicted particles sizes calculated with a model based on the Ostwald ripening mechanism were compared with the experimental data. The effect of solute availability, cooling rate and deoxidation practice on the particle population characteristics was determined. It was concluded that the amount, size and number of precipitating particles in Hadfield steel castings is possible to be controlled according to certain requirements by a careful selection of proper additives in proper amounts and also by the optimization of the casting process in aspects of deoxidation timing and control of the cooling rate of the castings.

  • 139.
    Siafakas, Dimitrios
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Matsushita, Taishi
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Lauenstein, Åsa
    Swerea SWECAST AB, Sweden.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ekengård, Johan
    Sandvik SRP, Sweden.
    The Influence of Deoxidation Practice on the As-Cast Grain Size of Austenitic Manganese Steels2017Inngår i: Metals, ISSN 2075-4701, Vol. 7, nr 6, artikkel-id 186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of in-situ precipitating particles on the grain size of Al-Ti-treated and untreated Hadfield steel cast in a pilot scale environment was studied. Hadfield steel was melted in an induction furnace and cast in Y-Block samples. Light Optical Microscopy (LOM) and the intercept method were utilized for the grain size measurements. Additionally, Thermo-Calc Software TCFE7 Steels/Fe-alloys database version 7 was used for thermodynamic equilibrium calculations of the mole fraction of particles. The planar disregistry values between the austenite and the precipitating particles were calculated. It was observed that increasing oxide content in samples with low Ti(CN) content resulted in a finer microstructure, while increasing the Ti(CN) content under similar oxide content levels led to a coarser microstructure. The potency of each type of particle to nucleate austenitic grains was determined. Spinel (MnAl2O4, MgAl2O4) particles were characterized as the most potent, followed by olivine (Mn2SiO4), corundum (Al2O3, TiO2), and finally Ti(CN), the least potent particle.

  • 140.
    Sjölander, Emma
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Payandeh, Mostafa
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, A. E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, M.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Thermal conductivity of liquid cast and rheocast telecom component using Al-6Si-2Cu-Zn (Stenal Rheo 1) in as-cast and heat treated condition2015Rapport (Annet vitenskapelig)
    Abstract [en]

    The thermal conductivity of a rheocast telecom component produced using Al-6Si-2Cu-Zn alloy (Stenal Rheo 1) was investigated in the as-cast, T5 and T6 conditions. Conventionally liquid cast samples were produced in a permanent mold and used as a reference material. In the rheocast component in as-cast condition, a thermal conductivity of 153 W/mK at room temperature were measured. A T5 treatment at 250 or 300°C increased thermal conductivity to 174 W/mK. A T6 treatment resulted in further increase in thermal conductivity to 182 W/mK. The liquid cast alloy exhibited a lower thermal conductivity and a higher hardness for all conditions compared to the as-rheocast component.The microstructure of rheocast component showed material consisted of relatively large α1-Al particles formed during the slurry fabrication process and fine α2-Al particles formed in the die cavity. The macrosegregation in the form of the different ration of the primary α1-Al particles to secondary α2-Al particles in different positions of the rheocast component was observed. The relation between microstructural characteristics and thermal diffusivity was investigated by determining the local thermal conductivity in the rheocast component and ration of α1-Al particles to α2-Al particles. The results revealed that samples from the regions of the component with a high amount of α1-Al particles had a higher thermal conductivity. WDS measurement results pointed to that Si and Cu concentration in the α1-Al particles contained lower concentrations value compare to the α2-Al particles and therefore α1-Al particles has higher value for thermal conductivity.Silicon precipitation was confirmed using calorimetry and dilatometry to take place between 200 and 250°C. A linear relation between the fraction of Si precipitates formed and the increase in thermal diffusivity was obtained. Silicon in solid solution is shown to have a strong influence (negative) on thermal conductivity. When the silicon is precipitated by heat treatment the thermal conductivity increases. For an optimal combination of thermal and mechanical properties it is therefore important to use an ageing temperature above the temperature for Si precipitation.

  • 141.
    Stolt, Roland
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    Elgh, Fredrik
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Challenges and Support when Introducing AM in HPDC Tooling2019Inngår i: Transdisciplinary engineering for complex socio-technical systems: Proceedings of the 26th ISTE International Conference on Transdisciplinary Engineering, July 30 – August 1, 2019 / [ed] K. Hiekata, B. Moser, M. Inoue, J. Stjepandić & N. Wognum, Amsterdam: IOS Press, 2019, s. 147-156Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When manufacturing tooling inserts for HPDC (High Pressure Die Casting), several manufacturing steps such as milling, heat treatment, electro discharge machining and finally surface treatment are involved. By instead manufacturing the insert by SLM (Selective laser melting), the process is expected to be quicker and with less material waste compared to the traditional manufacturing. Examples of other expected advantages is higher product variant flexibility and the possibility of making conform cooling channels, extending the die life. However, the insert is part of a die system involving many components. The insert cannot be designed and manufactured without considering the complete die system. This paper seeks how to integrate the insert design in the die assembly design. This is done via an example component and in cooperation with die manufacturing firms. The result is that the printing is a minor step of the total manufacturing process and that special design considerations needs to be taken for an SLM insert. New die concepts are needed that will minimise the amount of material, reduce the tolerance and surface demand and support the subdivision of the die into several printed parts.

  • 142. Su, C. W.
    et al.
    Oon, P. H.
    Bai, Y. H.
    Jarfors, A. E. W.
    Mechanical properties and microstructure of aluminum alloy Al-6061 obtained by the liquid forging process2010Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 654-656, s. 1420-1423Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The liquid forging process has the flexibilities of casting in forming intricate profiles and features while imparting the liquid forged components with superior mechanical strength compared to similar components obtained via casting. Additionally, liquid forging requires significantly lower machine loads compared to solid forming processes. Currently, components that are formed by liquid forging are usually casting alloys of aluminum. This paper investigates the suitability of liquid forging a wrought aluminum alloy Al-6061 and the mechanical properties after forming. The proper handling of the Al-6061 alloy in its molten state is important in minimizing oxidation of its alloying elements. By maintaining the correct alloying composition of Al-6061 after liquid forging, these Al-6061 samples can subsequently undergo a suitable heat treatment process to significantly improve their yield strengths. Results show that the yield strengths of these liquid forged Al-6061 samples can be increased from about 90MPa, when they are in the as-liquid forged state, to about 275MPa after heat treatment. This improved yield strength is comparable to that of Al-6061 samples obtained by solid forming processes. As such, the liquid forging process here has been shown to be capable of forming wrought aluminum alloy components that has the potential for structural applications. © (2010) Trans Tech Publications.

  • 143.
    Sujakhu, S.
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Castagne, S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Sakaguchi, M.
    Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, Japan.
    Kasvayee, Keivan Amiri
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Wang, W.
    Advance Remanufacturing and Technology Centre, Singapore.
    On the fatigue damage micromechanisms in Si-solution-strengthened spheroidal graphite cast iron2018Inngår i: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 41, nr 3, s. 625-641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphite nodules in spheroidal graphite cast iron (SGI) play a vital role in fatigue crack initiation and propagation. Graphite nodules growth morphology can go through transitions to form degenerated graphite elements other than spheroidal graphite nodules in SGI microstructure. These graphite particles significantly influence damage micromechanisms in SGI and could act differently than spheroidal graphite nodules. Most of the damage mechanism studies on SGI focused on the role of spheroidal graphite nodules on the stable crack propagation region. The role of degenerated graphite elements on SGI damage mechanisms has not been frequently studied. In this work, fatigue crack initiation and propagation tests were conducted on EN-GJS-500-14 and observed under scanning electron microscope to understand the damage mechanisms for different graphite shapes. Crack initiation tests showed a dominant influence of degenerated graphite elements where early cracks initiated in the microstructure. Most of the spheroidal graphite nodules were unaffected at the early crack initiation stage, but few of them showed decohesion from the ferrite matrix and internal cracking. In the crack propagation region, graphite/ferrite matrix decohesion was the frequent damage mechanism observed with noticeable crack branching around graphite nodules and the crack passing through degenerated graphite elements. Finally, graphite nodules after decohesion acted like voids which grew and coalesced to form microcracks eventually causing rapid fracture of the remaining section.

  • 144. Svendsen, L
    et al.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Al-Ti-C phase diagram1993Inngår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 9, nr 11, s. 948-957Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Equilibrium experiments have been performed at 1373, 1173, and 973 K, with alloys of compositions within the aluminium rich corner of the Al–Ti–C phase diagram. The samples have been metallographically investigated using light optical microscopy and a scanning electron microscope equipped with a system for energy dispersive spectrometry. Equilibrium phases, as well as effects of cooling, have been identified. Dynamic effects originating from cooling are discussed and a tentative phase diagram is proposed. It was predicted theoretically and confirmed experimentally that a class II reaction involving four phases occurs, i.e. Al(l) + TiC(s)Al3Ti(s) + Al4C3(s), below 1100 K.

  • 145.
    Tan, J. L.
    et al.
    Singapore Institute of Manufacturing Technology.
    Butler, D. L.
    Singapore Institute of Manufacturing Technology.
    Sim, L. M.
    Singapore Institute of Manufacturing Technology.
    Jarfors, A. E. W.
    Singapore Institute of Manufacturing Technology.
    Effects of laser ablation on cemented tungsten carbide surface quality2010Inngår i: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 101, nr 2, s. 265-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. © 2010 Springer-Verlag.

  • 146.
    Tarasov, Vladimir
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Datateknik och informatik, JTH, Jönköping AI Lab (JAIL).
    Tan, He
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Datateknik och informatik, JTH, Jönköping AI Lab (JAIL).
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Fuzzy logic-based modelling of yield strength of as-cast A356 alloy2019Inngår i: Neural computing & applications (Print), ISSN 0941-0643, E-ISSN 1433-3058Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Uncertain and imprecise data are inherent to many domains, e.g. casting lightweight components. Fuzzy logic offers a way to handle such data, which makes it possible to create predictive models even with small and imprecise data sets. Modelling of cast components under fatigue load leads to understanding of material behaviour on component level. Such understanding is important for the design for minimum warranty risk and maximum weight reduction of lightweight cast components. This paper contributes with a fuzzy logic-based approach to model fatigue-related mechanical properties of as-cast components, which has not been fully addressed by the current research. Two fuzzy logic models are constructed to map yield strength to the chemical composition and the rate of solidification of castings for two A356 alloys. Artificial neural networks are created for the same data sets and then compared to the fuzzy logic approach. The comparison shows that although the neural networks yield similar prediction accuracy, they are less suitable for the domain because they are opaque models. The prediction errors exhibited by the fuzzy logic models are 3.53% for the model and 3.19% for the second, which is the same error level as reported in related work. An examination of prediction errors indicated that these are affected by parameters of the membership functions of the fuzzy logic model.

  • 147.
    Thipprakmas, Sutasn
    et al.
    King Mongkuts Univ Technol Thonburi, Bangkok, Thailand.
    Aue-u-lan, Yingyot
    King Mongkuts Univ Technol North Bangkok, Bangkok, Thailand.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jirathearanat, Suwat
    Singapore Inst Mfg Technol SIMTech, Singapore, Singapore.
    Computational Methods in Design and Manufacturing Processes2019Inngår i: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, s. 1-1, artikkel-id 1920871Artikkel i tidsskrift (Fagfellevurdert)
  • 148.
    Wang, Yongsheng
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore .
    Tan, Ming Jen
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Corrosion performance of melt-spun Mg 67Zn 28Ca 5 metallic glass in artificial sweat2012Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, nr 18, s. 6586-6592Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Mg-based metallic glass developed in thisstudy provides an alternative for Mg alloys for being usedin daily life. In this study, the corrosion behaviors of meltspunMgZnCa ribbons with and without heat treatmentwere investigated in artificial sweat. Surface morphologyanalysis showed that amorphous ribbon was more sensitiveto suffer from pitting corrosion. Electrochemical testingand measurement of metal ion concentrations indicate thatribbons in amorphous structure were nobler with smallercorrosion current and possessed much slower dissolutionrate of metal ions. A Zn-rich passivation layer is detectedon the surface of amorphous ribbon, indicating that Zn ismore effective in amorphous ribbon to protect the inneractive metal.

  • 149.
    Wang, Yongsheng
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Tan, Ming Jen
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Corrosion Behavior and Surface Analysis of Melt-spun Mg-based Metallic Glass in Physiological Saline Solution2012Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 706-709, s. 606-611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The developed Mg-based metallic glass shows great potential as implants in biomedicalapplications instead of crystalline Mg alloys, which may possesses acceptable corrosion properties. Inthis study, corrosion behaviors of melt-spun amorphous Mg67Zn28Ca5 ribbons were investigated inphysiological saline solution. Electrochemical testing and hydrogen evolution rate indicated that theglassy ribbons obtained at lower wheel speed were more noble with smaller corrosion current, andpossessed a comparatively lower corrosion rate in physiological saline solution. Surface morphologyanalysis revealed that glassy Mg67Zn28Ca5 ribbons exhibited a strong susceptibility to localizedpitting corrosion. A Zn-rich passive layer was formed on the surfaces of the glassy ribbons, indicatingthat Zn was an effective alloying element to enhance the corrosion resistance of amorphousMg67Zn28Ca5 alloys.

  • 150.
    Wikedzi, Alphonce
    et al.
    University of Dar es Salaam, Tanzania.
    Sandström, Åke
    Luleå University of Technology, Sweden.
    Awe, Samuel A.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Luleå University of Technology, Sweden.
    Recovery of antimony compounds from alkaline sulphide leachates2016Inngår i: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 152, s. 26-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In copper metallurgy, antimony impurities usually form alloys and compounds with the transition metals to make up the basic building blocks of a speiss phase. This speiss phase is generally rich in copper and precious metals, which are desirable to recycle and recover at the smelter. The presence of this impurity unfortunately creates a build-up of this metal in the copper circuit, leading to problems during copper refining processes. Therefore, a removal or reduction of the antimony impurity to an acceptable level is a necessary step before the speiss can be recycled at the smelter for the recovery of its valuable metals. A lead silicate slag that was obtained after smelting a copper speiss admixed with silica, soda and lead oxide, was leached in alkaline sulphide solution to selectively dissolve its antimony content. Furthermore, the pregnant sulphide leachate was purified by precipitation and crystallization techniques to recover antimony as sodium thioantimonate and sodium hydroxyl antimonate using synthetic Na2S-NaOH-Sb2S3 solutions. The leaching results indicate that the highest amount of antimony and arsenic extracted from the material after 24 h at 100 °C and reagent concentration of 30 g/L NaOH + 30 g/L S2− was 83% and 90%, respectively. In the precipitation process, the addition of hydrogen peroxide to the alkaline sulphide leachate prompts the precipitation of antimony as NaSb(OH)6. The result also implies that b100% of stoichiometric hydrogen peroxide is required to completely oxidize the total amounts of both Sb3+ and S2− in the solution and to quantitatively precipitate N90% of the antimony in solution. The influence of catalytic agents and temperature on the process was not clearly reflected in this investigation due to the exothermic reaction with hydrogen peroxide. Moreover, the addition of elemental sulphur to the sulphide leachate also in- fluences the precipitation of antimony as sodium thioantimonate.

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