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  • 51.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components2018Inngår i: Metals, E-ISSN 2075-4701, Vol. 8, nr 7, artikkel-id 551Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combination of direct austempering after solidification (DAAS) treatment and electron backscatter diffraction (EBSD) method was used to study the formation of micro-shrinkage porosities in ductile iron. Analyzing the aus-ferritic microstructure revealed that most of micro-shrinkage porosities are formed at the retained austenite grain boundaries. There was no obvious correlation between the ferrite grains or graphite nodules and micro-shrinkage porosities. Due to the absolute pressure change at the (purely) shrinkage porosities, the dendrite fragmentation rate during the DAAS process would be altered locally, which caused a relatively finer parent-austenite grain structure near such porosities.

  • 52.
    Ghassemali, Ehsan
    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.
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University.
    Chua, Beng Wah
    Singapore Institute of Manufacturing Technology (SIMTech).
    Microstructure versus substructure size effect2016Inngår i: AIP Conference Proceedings / [ed] Francisco Chinesta, Elias Cueto and Emmanuelle Abisset-Chavanne, American Institute of Physics (AIP), 2016, Vol. 1769, s. 1-6, artikkel-id 090001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In metal deformation, size effect is generally attributed to the interactive effect of grain size and specimen dimension. This work shows, however, that relative substructure dimensions should also be considered. Micro-compression tests on the micro-pins having different grain sizes revealed no significant size effect with respect to the mechanical behavior, even if the number of grains over the diameter of the micro-pins falls below its critical value. To justify the reason laying under this fact, a recovery annealing cycle was applied on the micro-pins to change the substructure properties without altering the mean grain size. A surprising drop in the flow stress of the recovery-annealed micro-pins implied the importance of considering subgrain size rather than grain size over the diameter of component for the size effect investigation.

  • 53.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jarfors, Anders
    Sch. of Mech. & Aerospace Eng., Nanyang Technological University, Singapore.
    Tan, M.J.
    Sch. of Mech. & Aerospace Eng., Nanyang Technological University, Singapore.
    Lim, S.C.V.
    Singapore Institute of Manufacturing Technology (SIMTech)..
    Dead-zone formation and micro-pin properties in progressive microforming process2011Inngår i: ICTP 2011, 10th International Conference on Technology of Plasticity, Steel Research International: Special Edition, Aachen, DE, Sep 25-29, 2011, Weinheim: Wiley-VCH Verlagsgesellschaft, 2011, nr 9, s. 1014-1019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel progressive microforming process that consisted of a two step operations, punching and blanking was studied. Micropins with diameter of 300 µm were manufactured from metal strip to cater for a set-up with good potential for mass production. Investigations showed that the microstructure contains some deformed zones surrounded by less-deformed zones or "dead-zones" which is unique to the progressive microforming process. The aim of this work was to understand the origin and evolution of the "dead-zones" in the microstructure of the final products during the progressive microforming process, and find a way to avoid this phenomenon. To do this, the microstructure of the 300 µm pins with punch diameters of 3.2 and 2.2 mm at different punch displacement was investigated experimentally and by simulation. Experimental observations showed that dead-zones appear just after starting the microforming process, which is due to the friction at the workpiece-die interface. This dead zone leaks into the die cavity as a result of work-piece compression. It was shown that the inhomogeneous mechanical properties could be significantly improved by selection of an appropriate punch.

  • 54.
    Ghassemali, Ehsan
    et al.
    School of Mechanical & Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University.
    Chua, Beng Wah
    Singapore Institute of Manufacturing Technology (SIMTech).
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Lim, S.C.V.
    Materials Engineering, Monash University.
    Grain size and workpiece dimension effects on material flow in an open-die micro-forging/extrusion process2013Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 582, nr 10, s. 379-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interactive effect of grain size and specimen dimensions on the material flow and microstructural evolution was studied in a progressive open-die microforming process. Particular interest was paid on the effect of the number of grains over the initial specimen thickness, on the evolution of the dead metal zone (DMZ) in the final micro-component's microstructure. Such a DMZ is deemed unfavorable for mechanical properties of the pin. Interestingly, experimental results revealed that the DMZ can be removed at the pin surface by increasing the initial grain size. This behavior was attributed to the role of the strain gradient on the deformation. In the aspects of the forming load and dimensional measurements of the final parts, there were no significant size-effects observed in this process. This is because the neutral plane, which demarcates the two directions of material flow in the open-die forging/extrusion process, determines the amount of material flow towards the die orifice, regardless of the initial grain size.

  • 55.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. School of Mechanical & Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University.
    Chua, Beng Wah
    Singapore Institute of Manufacturing Technology (SIMTech).
    Lim, Samuel C.V.
    Materials Engineering, Monash University.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Friction effects during open-die micro-forging/extrusion processes: An upper bound approach2014Inngår i: Procedia Engineering / [ed] Ishikawa, T, Mori, KI, Elsevier, 2014, Vol. 81, s. 1915-1920Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In microforming processes it is preferred to not to use lubricants, due to their complex behavior in micro-scale. Nevertheless, using lubricants could increase the life time and decrease the required forming load. Thus, it is necessary to study and develop an analytical solution for different lubrication conditions in microforming processes. A previously studied upper bound model was modified in this study for various lubrication conditions in an open-die micro-forging/extrusion process. Two approaches were chosen for identifying the friction factor in the model: (i) global friction factor, (ii) localized friction factor. Comparison of the modeling results with the experimental showed the reliability of the second approach, providing a better fit.

  • 56.
    Ghassemali, Ehsan
    et al.
    School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore.
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Lim, S.C.V.
    Materials Engineering, Monash University, Wellington Road, Clayton, Victoria, Australia.
    Optimization of axisymmetric open-die micro-forging/extrusion processes: An upper bound approach2013Inngår i: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 71, s. 58-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a trend towards component miniaturization and strong drive towards cost effective and sustainable metal forming techniques of miniaturized components. This paper presents an upper bound solution for the optimization of open-die forging/extrusion processes in the forming of micro-pins from a sheet metal. Using such an analytical modeling approach, the critical blank thickness, the resulting final part geometry, together with the required forming load were predicted based on the location of the neutral plane under the punch during the process. Based on the phenomenological findings of the process, the geometry size factor, x, was introduced explaining its relative importance to the model. Experimental results obtained from C11000 copper samples using a progressive microforming process was found to agree well with the results predicted by the model. The results were also validated with other results reported before from a similar process.

  • 57.
    Ghassemali, Ehsan
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical and Aerospace Engineering, Nanyang Technological University.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Lim, S.C.V.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Progressive microforming process: Towards the mass production of micro-parts using sheet metal2013Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 66, nr 5-8, s. 611-621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although there is considerable published literature on micro-metal forming processes, there is still a lack of research towards implementing these processes commercially. Some of the challenges are handling of micro-parts and process intermittency. This work demonstrates the feasibility of producing symmetric micro-parts using a progressive forming set-up. Such a progressive forming process alleviates the challenges in handling and removal of micro-parts. Micro-pins with diameters of 0.3, 0.5, and 0.8 mm were successfully manufactured without defects. Experimental observations together with process simulation results showed that this process has three main stages: (1) indentation at the very beginning, (2) upsetting, and (3) extrusion predominantly occurring at the very end stage of the stroke. The bulk of the pin forming occurs at the end stroke of the process (extrusion stage). The effects of punch/pin diameter ratio on the pin aspect ratio and the maximum forming load were also investigated. In addition, the finite element results also revealed that a hybrid friction model was required to be implemented for better fit with experimental results as compared to the shear and Coulomb friction models.

  • 58.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Nanyang Technological University, Singapore; Singapore Institute of Manufacturing Technology, Singapore.
    Tan, Ming-Jen
    Nanyang Technological University, Singapore.
    Lim, Samuel Chao Voon
    Monash University, Clayton, Australia.
    Wah, Chua Beng
    Singapore Institute of Manufacturing Technology, Singapore.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Experimental and Simulation of Friction Effects in an Open-Die Microforging/Extrusion Process2014Inngår i: Journal of Micro and Nano-Manufacturing, ISSN 2166-0468, Vol. 2, nr 1, s. 011005-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Friction effects during a progressive microforming process for production of micropins of various diameters were experimentally investigated and were analytically modeled, using a hybrid friction model. The response surface method and ANOVA analysis were used to generalize the findings for various pin diameters. Besides, it was shown that to get an accurate result in simulation, the friction model must be considered locally instead of a global friction model for the whole process. The effect of friction factor on the final micropart dimensions (the effect on the instantaneous location of the neutral plane) and the forming pressure were investigated. The results showed a reduction in the friction factor as die diameter increased. Following that, the optimum frictional condition to obtain the highest micropart aspect ratio was defined as the maximum friction on the interface between the die upper surface and the punch surface, together with a minimum friction inside the die orifice.

  • 59. Ghassemali, Ehsan
    et al.
    Tan, Ming-Jen
    Lim, Samuel C.V.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Friction Factor in a Progressive Microforming Process2012Inngår i: 7 th INTERNATIONAL CONFERENCE ON MICROMANUFACTURING, 2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this work, the effect of global and localized friction factoron the material forming in the simulation is investigated. Tomatch the simulation and experimental results, a reverse engineeringmethod has been used to get the correct frictionfactor for the defined condition in the microforming process.The friction size effect in the progressive microformingprocess has also been addressed.

  • 60.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Tan, Ming-Jen Tan
    School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore.
    Wahb, Chua Beng
    Singapore Institute of Manufacturing Technology (SIMTech), Singapore.
    Lim, S.C.V.
    Materials Engineering, Monash University, Australia.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Effect of cold-work on the Hall–Petch breakdown in copper based micro-components2015Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 80, part A, s. 124-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effects of substructural dimensions on the mechanical properties of micro-pins produced by an open-die micro-extrusion/forging process were studied. Micro-pins of diameter 0.3 mm were manufactured from copper strips, having different initial grain sizes. Micro-compression tests on the micro-pins revealed no significant size effect, even if the number of grains over the diameter of the micro-pins falls below its critical value. However, relaxation of the as-formed substructure using recovery annealing led to a surprising drop in the flow stress of the micro-pins. This was explained and attributed to the number of subgrains over the diameter of the micro-pins, showing the important role of subgrains rather than grains in determining the mechanical properties.

  • 61.
    Goh, C. S.
    et al.
    Singapore Institute of Manufacturing Technology.
    Gupta, M.
    Department of Mechanical Engineering, National University of Singapore.
    Jarfors, A. E. W.
    Singapore Institute of Manufacturing Technology.
    Tan, M. J.
    School of Mechanical and Aerospace Engineering.
    Wei, J.
    Singapore Institute of Manufacturing Technology.
    Magnesium and Aluminium carbon nanotube composites2010Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 425, s. 245-261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon nanotubes are one of the most exciting discoveries of nanosized materials in the 20th century. Challenges to create materials applicable for industrial applications involve both the incorporation of the carbon nanotubes into the material and to ensure that they do not agglomerate. Aluminium and magnesium based materials are among the metals that can benefit from the incorporation of carbon nanotubes. The fabrication of Aluminium carbon nanotube composites has challenges from reactivity and degradation of the carbon nanotube additions; hence the powder metallurgy route is preferred. Magnesium based materials on the other hand do not have this limitation and both the powder metallurgical route and the casting route are viable. Among the benefits of adding carbon nanotubes are increased yield strength and stiffness. Here is important that the effect is significant already at very low addition levels. This makes it possible to increase strength without having a significant detrimental effect on ductility. In fact, for magnesium alloys ductility can be improved due to the activation of additional slip planes improving the normally low ductility of HCP structure materials. © (2010) Trans Tech Publications.

  • 62.
    Goi, K. L. S.
    et al.
    Ametek, Singapore.
    Butler, D. L.
    Nanyang Technological University, Singapore.
    Jarfors, A. E. W.
    KIMAB, Stockholm, Sweden.
    Yong, J. M. S.
    Singapore Institute of Manufacturing Technology.
    Lim, D. C. S.
    Nanyang Technological University, Singapore.
    Elastic modulus of sintered porous Ti-Si-Zr, using activation by Ti-Si mechanically alloyed powder and TiH2 powder2008Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 475, nr 1-2, s. 45-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel biomaterial based on Ti-Si-Zr was developed using the sintering process with a composition targeting at a bulk modulus in the same range as that of human bone, i.e. 10-30 GPa. Control of porosity should also be possible to allow for the promotion osseointegration. The sintering procedure involves the use of mechanically alloyed Ti-Si-powder, and TiH2, to promote bonding, but not consolidation. The effect of porosity on the bulk modulus using compression testing is investigated. The influence of sintering temperature, heating rate, and amount and size of the TiH2-activator on porosity are also investigated. The achievable bulk modulus was in the range of 20-55 GPa at porosity levels ranging from 16% to 54%. Porosity had a profound influence on the bulk modulus, and the choice of appropriate processing conditions enables the creation of an engineered porosity and bulk modulus primarily by varying the sintering temperature and the size of the TiH2-powder particles. © 2007.

  • 63.
    Gu, Y. W.
    et al.
    Singapore Institute of Manufacturing Technology.
    Goh, C. W.
    Singapore Institute of Manufacturing Technology.
    Goi, L. S.
    Singapore Institute of Manufacturing Technology.
    Lim, C. S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Nanyang Avenue, Singapore.
    Jarfors, A. E. W.
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Tay, B. Y.
    Singapore Institute of Manufacturing Technology.
    Yong, M. S.
    Singapore Institute of Manufacturing Technology.
    Erratum: "Solid state synthesis of nanocrystalline and/or amorphous 50Ni-50Ti alloy" (Materials Science Engineering A (2005) vol. 392 (222-228) 10.1016/j.msea.2004.09.025))2005Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 402, nr 1-2, s. 349-350Artikkel i tidsskrift (Fagfellevurdert)
  • 64.
    Gu, Y. W.
    et al.
    Singapore Institute of Mfg. Technol..
    Goh, C. W.
    Singapore Institute of Mfg. Technol..
    Goi, L. S.
    Singapore Institute of Mfg. Technol..
    Lim, C. S.
    School of Mechanical/Production Eng., Nanyang Technological University, Nanyang Avenue, Singapore.
    Jarfors, A. E. W.
    Swedish Inst. for Metals Research, Stockholm, Sweden.
    Tay, B. Y.
    Singapore Institute of Mfg. Technol..
    Yong, M. S.
    Singapore Institute of Mfg. Technol..
    Solid state synthesis of nanocrystalline and/or amorphous 50Ni-50Ti alloy2005Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 392, nr 1-2, s. 222-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A nanocrystalline/amorphous 50Ni-50Ti alloy was produced by solid state synthesis via mechanical alloying from elemental Ti and Ni powders. Using X-ray diffraction analysis and transmission electron microscopy techniques, a mechanically induced solid state reaction of 50Ni-50Ti was investigated. Results showed that nanocrystalline and amorphous Ni-Ti phases were obtained after mechanical alloying. The mechanical alloying of 50Ni-50Ti for 270 ks led to the formation of f.c.c. Ni(Ti) solid solution, characterized by a lattice parameter of 0.3558 nm, crystallite size of 14 nm and lattice strain of 0.98%. The particle size decreased with increasing milling time. The crystallite size of mechanically alloyed 50Ni-50Ti powders was substantially refined as the milling proceeded and the lattice strain increased with the milling time. The steady-state crystallite size was approximately 10-15 nm. The internal lattice strain in Ni-Ti alloy led to the disordering and the subsequent formation of amorphous alloy during mechanical alloying. After heat treatment at 1100 °C, the as-milled powders transformed into B2-NiTi phase and a small amount of Ti2Ni phase. © 2004 Elsevier B.V. All rights reserved.

  • 65.
    Gu, Y. W.
    et al.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Goi, L. S.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Jarfors, A. E. W.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Butler, D. L.
    Sch. of Mech./Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
    Lim, C. S.
    Sch. of Mech./Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
    Structural evolution in Ti-Si alloy synthesized by mechanical alloying2004Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 352, nr 1-4, s. 299-304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical alloying of Ti-Si powder mixture was performed by high-energy ball milling at ambient temperature (25 °C). The structural and compositional evolutions during the mechanical alloying process were investigated by X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. Results showed, that the crystallite size of Ti and Si decreased with increasing milling time and the steady-state crystallite size was between 5 and 15nm. The mechanically alloyed Ti-Si powder was predominantly nanocrystalline with traces of the remnant amorphous phase. It was found that a significant increase in solid solubility of Si in Ti was achieved by mechanical alloying. Interdiffusion between the two elements occurred during milling and the dissolution of Si in Ti was obtained after 60 h milling, forming Ti(Si) solid solution. The lattice parameter ratio c/a and the unit cell volume of h.c.p. Ti(Si) were found to decrease with increasing milling time, indicating that the shrinkage of Ti lattice was caused by diffusion of Si atoms into Ti. © 2004 Elsevier B.V. All rights reserved.

  • 66.
    Jarfors, A. E. W.
    Singapore Inst. of Mfg. Technology, Process Technology Division, Precision Metal Forming Group, Singapore.
    A Discussion of the Dynamic Specific Heat during Solidification2003Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 437-438, s. 391-394Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    State-of-the-art solidification theory shows that the apparent latent heat of fusion decreases with increasing cooling rates, due to the creation of lattice defects. A portion of the defects condenses during and after solidification, releasing heat, causing the apparent specific heat to be dynamic. Experimental data on copper shows an increase and a maximum in the apparent specific heat at moderate cooling rates. An extension of the existing theory for dynamic specific heats is made. Previous models do not reproduce the maximum, nor do they reproduce the equilibrium value at low cooling rates. The presently derived model reproduces all essential features of the experimentally data. It also clearly shows that the effect at moderate cooling rates is significant and the tabulated values are not applicable for modelling casting.

  • 67.
    Jarfors, A. E. W.
    KTH-IMP/MG, Stockholm, Sweden.
    Influence of carbon on the phases in the copper-titanium system and their precipitation1999Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 34, nr 18, s. 4533-4544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of carbon on the phases occurring in the copper-titanium system has been experimentally investigated. Samples were fabricated from elemental copper and titanium. Carbon was added in the form of graphite or as titanium carbide. The samples were encapsulated, heat-treated at 1173 or 1373 K for 24 h and subsequently quenched in brine. The phases present at the treatment temperature were identified, as well as the phases occurring during solidification. The microstructure indicates the presence of a miscibility gap. The composition of the phases were determined using EDS-analysis. The composition of the copper phase was found to show a great variation caused by the precipitation sequence during quenching of the melts. The complex precipitation also caused both TiCu4 and the meta-stable TiCu3 to form. The composition of TiCu was found to show a wider compositional interval than earlier found. The variation of its composition with the nominal composition suggests that TiCu can dissolve carbon. The pure Ti phases also showed larger solubility of copper than earlier found. An outline of the precipitation sequence is made.

  • 68.
    Jarfors, A. E. W.
    Swed. Institute for Metals Research, Stockholm, Sweden.
    Melting and coarsening of A356 during preheating for semisolid forming2004Inngår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 17, nr 4, s. 229-237Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The melting and coarsening behaviour of A356 during preheating for semisolid forming has been investigated theoretically and experimentally. The preheating involves a relatively rapid heating and a partial melting, transforming the material into a mushy state, i.e. a mixture of solid particles and melt. The experiments reveal a change in melting behaviour over the temperature interval 580-590°C, where a re-solidification occurs during heating. During the initial phase of melting, the smallest solid particles melt completely and larger particles are split into smaller particles, making the shape of the particles more irregular. Particle fragmentation influences the occurrence of the enclosed eutectic, which temporarily maintains a higher solid fraction as a result of increased diffusion distances. Resolidification and coarsening contribute to a rapid particle size increase. The model derived fits the experimental series well and supports the coarsening and particle fragmentation observations. © 2004 W. S. Maney & Son Ltd.

  • 69.
    Jarfors, A. E. W.
    Department of Materials Processing, Royal Institute of Technology, Metals Casting Research Group, Stockholm, Sweden.
    On the design of a rotary spray former: Experimental and theoretical background1997Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 71, nr 3, s. 440-455Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phenomenological theory for jet stability and spray formation in centrifugal spraying is reviewed and investigated experimentally. The appropriate set of equations is then adapted to the phenomena found in the present study. The flow on the disk is treated both theoretically, as well as experimentally, leading to the possible design of a spray former. The droplet formation mechanisms are studied implicitly in the experiments, three different modes being found. A bi-modal spray is formed from the disk edge by two modes of disintegration, whilst the third mode is caused by instability at jet impact on the disk and causes a tri-modal spray. The boundary conditions for the release and flight of the droplets are treated theoretically and correlated experimentally. Water was used initially as a model material, due to the ease of direct visual observation, the knowledge acquired then being used to interpret experiments where an A17Si0.3Mg alloy is sprayed. The experimentally-obtained parameters are used in a theoretical treatment to predict the flow on the disk, i.e. the spray directions and the flight of the droplets. The general conclusion is that it is feasible to design a rotary spray former with a directed flow, the key issue being to control the jet width and the actual droplet formation at the disk edge. ©1997 Elsevier Science S.A.

  • 70.
    Jarfors, A. E. W.
    Royal Institute of Technology, KTH, Department of Materials Processing, Stockholm, Sweden.
    Peritecticlike precipitation of titanium carbide in Al-Ti-C melts at 1373 K1999Inngår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 15, nr 5, s. 481-494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction between an Al-Ti melt and a carbon containing medium, i.e. pure graphite or molten aluminium containing aluminium carbide, was studied. Experiments were carried out at 1373 K, using three different experimental setups. Depending on the carbon source, titanium carbide precipitated as a layer or as free particles. Classical nucleation theory for homogeneous and heterogeneous nucleation is used to assess the surface tension. The influence of stoichiometry on surface tension and nucleation is discussed. The formation of a continuous layer, or peritecticlike precipitation of titanium carbide, is theoretically analysed. The growth of the layer is rate controlled by the mass transfer of carbon at the interface, plausibly as a result of the ordering tendencies in titanium carbide. The degeneration of precipitation into that of freely formed particles is found to be nucleation controlled. A model for degenerate precipitation is proposed, including predictions of the reaction front compositions, growth rate, and particle fractions in a dilute ternary system. The model is in good agreement with experiments, after compensating for settling of the precipitates, except in predicting the precipitated fractions. © 1999 IoM Communications Ltd.

  • 71.
    Jarfors, A. E. W.
    Royal Institute of Technology, Department of Materials Processing, Stockholm, Sweden.
    Solidification behaviour of AI-7% Si-0.3% Mg during rotary spray forming1998Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 33, nr 15, s. 3907-3918Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The solidification behaviour of an AI-7% Si-0.3% Mg alloy during rotary spray forming was studied. The ability to form a coating was insensitive to the thermal processing parameters, yielding material exchangess greater than 90%. The level of porosity varied typically between 1.5 and 4.75%. The dendrite arm spacing was evaluated and used to estimate the cooling rates. Typical dendrite secondary arm spacings were of the orderof 3 jam, 12 (am and 25 ÎŒm, corresponding to cooling rates of 4630 K s-1 72 K s-1 and 8 K s -1 respectively. The fraction primary precipitation was experimentally determined and the partition coefficient calculated indirectly using the Scheil equation. The partition coefficient is increased during rotary spray forming. This is explained by the presence of trapped vacancies at the solidification front. The vacancies change the solid's free energy and thus change the phase diagram and the partition coefficient. A simplistic analysis of entrapment and condensation of vacancies and their influence on the partition coefficient is made. © 1998 Kluwer Academic Publishers.

  • 72.
    Jarfors, A. E. W.
    Department of Materials Processing, Royal Institute of Technology, Stockholm, Sweden.
    Solubility of copper in titanium carbide1996Inngår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 12, nr 12, s. 990-994Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The solubility of copper in titanium carbide (TiCx) was studied experimentally. The solubility was assessed in two different ways: (a) titanium carbide was added to a copper-titanium melt, (b) titanium carbides formed in situ, from graphite and titanium, were analysed. The stoichiometries were implicitly assessed. The solubility of copper in titanium carbide was found to decrease with increasing carbon content. This behaviour was compared to the solubility of chromium in titanium carbide, which increases in solubility with increasing carbon content. The role of vacancies in the solution is briefly discussed. © 1996 The Institute of Materials.

  • 73.
    Jarfors, A. E. W.
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Butler, D. L.
    Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore.
    Goi, K. L. S.
    Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore.
    Microstructure formation of porous sintered Ti-Si-Zr compacts with mechanically alloyed-activated Ti-Si and TiH2 powders2014Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 594, s. 202-210Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metallic implants are widely used in applications associated with bone. A major drawback of using metals is their elastic modulus which is higher than that of bone resulting in stress shielding and premature failure of the implant. The employment of biomaterials with a porous structure has the potential to lower the modulus and promote osseointegration. The present work investigates the microstructure formation and the resulting elastic modulus of a new Ti-Si-Zr alloy. The sintering procedure involves the use of both mechanically alloyed Ti-Si powder and TiH2 to activate sintering with the TiH2 also serving as a pore precursor. The procedure is designed to promote bonding but not consolidation. The influence of sintering temperature, heating rate, as well as the amount and size of the TiH2 on the phases formed and porosity was investigated. It was observed that the use of TiH2 increased the degree of porosity whilst the size of TiH2 particles could be used to control the pore size. The results showed that when using small TiH2 particles, the elastic modulus was strongly dependent on the fraction of TiH2. When large TiH2 particles were used, the porosity had no significant influence on the elastic modulus. The variation in behavior could be attributed to differences in microstructure. To control the bulk modulus it is essential to understand the differences in the microstructure formation mechanisms between these two cases. (C) 2014 Elsevier B.V. All rights reserved.

  • 74.
    Jarfors, A. E. W
    et al.
    Department of Materials Processing, Royal Institute of Technology, Metal Casting Research Group, Kungl Tekniska Hogskolan, Stockholm, Sweden.
    Keife, H.
    Outokumpu Copper, Process Automation, Västerås, Sweden.
    Antonsson, T.
    Department of Materials Processing, Royal Institute of Technology, Metal Casting Research Group, Kungl Tekniska Hogskolan, Stockholm, Sweden.
    Deformation enhanced liquid phase sintering (DELPS): A study on the use of partial adiabatic melting during powder consolidation2002Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 127, nr 2, s. 159-164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of a liquid phase enhances the pore closure of a porous body, which is used in liquid phase sintering (LPS). During LPS, a substantial grain growth may occur by coalescence or Ostwald ripening, thus a short time in the liquid state is advantageous. Furthermore, it has been shown that during the initial stage of LPS, agglomerates are disintegrated and a significant reduction of grain size occurs. Heavy deformation causes an adiabatic temperature increase, which may result in a partial melting of the powder. Short-time duration deformation-assisted LPS, so called deformation enhanced LPS (DELPS), may thus be a suitable route for the fabrication of difficult-to-form materials. The present study is a feasibility test of DELPS. Three different types of materials were tested. The first type was an Al-Si with the possibility to form a large fraction of liquid phase. The second type was a W-based powder mixture yielding a low fraction liquid. The third type was a Ni-Al powder mixture exhibiting an exothermal behaviour when reaction occurs. The powders were hot compacted in a flexible die allowing large deformations. The specimens were examined and the composition of the phases were analysed. All of the samples, but one, showed near full density (>98%). Evidence of melting was found and in the W-base and the Ni-Al powder mixtures, and reaction had occurred in the Ni-Al mixture. © 2002 Elsevier Science B.V. All rights reserved.

  • 75.
    Jarfors, A. E. W.
    et al.
    Singapore Inst. of Mfg. Technology, Process Technology Division, Precision Metal Forming Group, Singapore.
    Sim, G. C.
    Singapore Inst. of Mfg. Technology, Process Technology Division, Precision Metal Forming Group, Singapore.
    San, T. E.
    Singapore Inst. of Mfg. Technology, Process Technology Division, Precision Metal Forming Group, Singapore.
    Influence of Process Parameters on Reaction Products during Self-Propagating High-Temperature Synthesis of Porous NiTi2003Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 437-438, s. 475-478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    NiTi is proposed to be a biomaterial suitable for bone replacements. Reactive synthesis, Self-Propagating High-Temperature Synthesis (SHS) of NiTi from Ni and Ti powder is a suitable method to produce porous structures to promote osseointegration. The influence of pressed density and ignition temperature on the reaction products formed is investigated. Porosity after pressing was 20%, 30% and 40 % and ignition temperatures were 400°C, 500°C and 600°C. The reaction products found were NiTi, as well as Ti2Ni and Ni3Ti, in addition to residual Ni and Ti. The amount of NiTi formed increases with ignition temperature, with a maximum at an initial porosity of 30% and ignition temperature of 600°C. This coincides with the minimum amount of residual Ni and Ti. The reaction imbalance is caused by the formation of Ti2Ni at high pressed densities and by a preferential nucleation of Ni3Ti, both suggested to be dominated by the effective contact area between the Ni and Ti particles after pressing.

  • 76.
    Jarfors, A. E. W.
    et al.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Tong, S.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Hu, B.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Sharma, S. N.
    Integrated Magnesium Techologies, Singapore.
    Wee, C.
    Integrated Magnesium Techologies, Singapore.
    Mechanism of lubrication-induced surface cracking in hot chamber die cast thin-walled AZ91D parts2003Inngår i: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 18, nr 4, s. 637-641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin-walled hot chamber die cast parts are often used to make telephone casings and similar products having primarily requirements on weight and aesthetically satisfying surfaces. The post casting surface treatment often generates a glossy appearance. The glossy appearance makes it extremely sensitive to small-scale flaws, such as blisters, cold shuts, and cracks. Hot chamber die casting of thin-walled parts requires high filling speed and the use of lubrication because the parts have high aspect ratios. In the manufacturing of such high aspect ratio parts with a wall thickness of 0.6 mm, a new type of cold crack induced by the lubrication is observed. To some extent this defect is similar to a blister, but the characteristic bump is not formed and the actual crack is formed by thermal contraction along the high aspect ratio areas.

  • 77.
    Jarfors, A. E. W.
    et al.
    Singapore Institute of Manufacturing Technology.
    Yong, J. M. S.
    Singapore Institute of Manufacturing Technology.
    Kainer, K. -U
    GKSS Forschungszentrum Geesthacht Gmbh, Germany.
    Tan, M. -J
    Nanyang Technological University, Singapore.
    Preface2010Inngår i: Materials & Design, ISSN 0261-3069, Vol. 31, nr SUPPL. 1, s. S1-Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 78.
    Jarfors, A.
    et al.
    Casting of Metals, Royal Institute of Technology, Stockholm, Sweden.
    Fredriksson, H.
    Casting of Metals, Royal Institute of Technology, Stockholm, Sweden.
    Froyen, L.
    Department MTM, Katholieke Universiteit Leuven, De Croylaan 2, B-3030 Heverlee, Belgium.
    On the thermodynamics and kinetics of carbides in the aluminium-rich corner of the AlTiC phase diagram1991Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 135, nr C, s. 119-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aluminium composites have a great potential because of their high strength-to-weight ratio. Carbides will in the future be powerful reinforcements. To be able to manufacture these it is of importance to know the thermodynamic properties and the kinetic limitations. The objective of this investigation is to study the equilibria between the carbides occurring in the AlTiC system as well as the initial precipitation and dissolution behaviour of these carbides. It can be shown that there is a change in stability between TiC and Al4C3, depending on both composition and temperature. To study the nucleation and precipitation behaviour of the carbides in liquid aluminium and aluminium alloys a set of alloys were melted and heated to an appropriate temperature in graphite crucibles. The effect of time and the effect of composition on the chemical reactions involving carbides have been investigated. A theoretical analysis of both the thermodynamics and kinetics was performed, giving a tentative explanation. © 1991.

  • 79.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Casting Alloy Design and Modification2016Inngår i: Metals, ISSN 2075-4701, Vol. 6, nr 1, artikkel-id 15Artikkel i tidsskrift (Annet vitenskapelig)
  • 80.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Insitu formed aluminium composites1998Inngår i: Advanced light alloys and composites, 1998Konferansepaper (Fagfellevurdert)
  • 81.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Special section: Selected papers from the 3rd international Conference on Cast Metal matrix Composites2001Collection/Antologi (Fagfellevurdert)
  • 82.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Yielding and failure of hot chamber die cast thin-walled AZ91D2016Inngår i: Metallurgia Italiana, ISSN 0026-0843, Vol. 108, nr 6, s. 53-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin-walled components in AZ91D magnesium are commonly cast using hot chamber die casting. AZ91D mechanical properties commonly show scatter and its low critically resolved shear stress cause early yield with an ill-defined yield point. This may result in large differences between the true yield point or proportionality limit and the off-set proof stress. The current study takes a look at this and its relation to the failure of the component. The material investigated was a hot chamber die cast material with a wall thickness of 0.8mm. Tensile tests were made and the proportionality limit and off-set proof stress was established as well as elongation to failure and tensile strength. The overall average off-set proof stress was 154 MPa and the overall proportionality limit was 63 MPa resulting in a typical property Stress Gap of 91MPa. This difference varied from 65MPa up to 105MPa. The Apparent Toughness was also evaluated The Stress Gap and Apparent Toughness was analysed and the influence of process parameters established.

  • 83.
    Jarfors, Anders E. W.
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Castagne, Sylvie J.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Danno, Atsushi
    Singapore Institute of Manufacturing Technology, Singapore.
    Zhang, Xinping
    School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, China.
    Tool wear and life span variations in cold forming operations and their implications in microforming2017Inngår i: TECHNOLOGIES, ISSN 2227-7080, Vol. 5, nr 1, artikkel-id 3Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The current paper aims to review tooling life span, failure modes and models in cold microforming processes. As there is nearly no information available on tool-life for microforming the starting point was conventional cold forming. In cold forming common failures are (1) over stressing of the tool; (2) abrasive wear; (3) galling or adhesive wear, and (4) fatigue failure. The large variation in tool life observed in production and how to predict this was reviewed as this is important to the viability of microforming based on that the tooling cost takes a higher portion of the part cost. Anisotropic properties of the tool materials affect tool life span and depend on both the as-received and in-service conditions. It was concluded that preconditioning of the tool surface, and coating are important to control wear and fatigue. Properly managed, the detrimental effects from surface particles can be reduced. Under high stress low-cycle fatigue conditions, fatigue failure form internal microstructures and inclusions are common. To improve abrasive wear resistance larger carbides are commonly the solution which will have a negative impact on tooling life as these tend to be the root cause of fatigue failures. This has significant impact on cold microforming.

  • 84.
    Jarfors, Anders E.W.
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Zheng, Jinchuan
    China Academy of Machinery Sciences and Technology (Jiangle) Institute of Semi-solid Metal Technology, Sanming, China.
    Chen, Liang
    RheoMet Light Metal Co., Ltd, Jiangle Economic Development Zone, Sanming, China.
    Yang, Jie
    KinRui Hi-Tech Co. Ltd, Sanming, China.
    Recent advances in commercial application of the rheometal process in China and Europe2019Inngår i: Semi-Solid of Alloys and Composites / [ed] Rassili A.,Midson S.P.,Zhu Q.,Gang Hu X., Trans Tech Publications, 2019, s. 405-410Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent advances in rheocasting have resulted in significant expansion in the types of products currently in full commercial production. The current paper gives an overview of components in production in Europe and in China produced using the RheoMetal™ process, that has taken the lead in a strong drive towards new heavy-duty applications made from aluminium alloys. In China, the dominating applications are found in the telecom industry. The trend in Europe is more towards marine and automotive applications commonly in fatigue loaded applications. The reason for the choice of rheocasting for complicated shape thin-walled electronics components with requirements is dominated by process yield and by the ability to improve thermal conductivity. The heavy-duty truck chassis thick walled components target weight reduction through design and to sustain fatigue load normally requiring forged components. Common in all applications are seen in production yield, reduced tool wear and reduction of die soldering.

  • 85.
    Jarfors, Anders
    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.
    Bogdanoff, Toni
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Börrisson, Markus
    SWEREA Swecast.
    Beste, Ulrik
    VBN Components AB.
    Effect of Use in High Pressure Die Casting on Vibenite®60 Tool Inserts Madeby Additive Manufacturing2016Inngår i: DDMC2016 Frauenhofer Direct Digital Manufacturing Conference: Conference Proceedings, March 2016, Berlin, Germany / [ed] B. Müller, Fraunhofer IRB Verlag, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The thermo-physical and mechanical properties of Vibenite®60 was investigated in the as-manufactured, soft annealed and hardened state as well as after use in full scale high pressure die casting. Thermal conductivity in the as manufactured state was 23.3 to 27.5 W/mK in the temperature range from 25°C to 500°C. Annealing increased thermal conductivity to 25.0 up to 29.2 W/mK. Hardening reduced thermal conductivity of 19.8 to 26.1 W/mK. The tool wastested in production in the as fabricated state displayed a slight increase in thermal conductivity, which was interpreted as a slight tempering during use. Hardness measurements were made at room temperature and followed the same pattern as the thermo-physical properties. Rockwell and Vickers Hardness was lowest in the as lowest in the annealed state and hardest in the hardened state. Rockwell hardness was not affected by use in production while Vickers hardness decreased slightly.

  • 86.
    Jarfors, Anders
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Rigovacca, Diego
    University of Padua, Italy.
    Payandeh, Mostafa
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Wessén, Magnus
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Jansson, Per
    COMPtech.
    Influence of process parameters on surface appearance and roughness of a low Si containing Al-alloy, in semisolid casting2015Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 217-218, s. 318-324Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The visual appearance and surface roughness were experimentally investigated inindustrial scale for a low silicon containing aluminium alloy cast in semisolid state integrated withHPDC machine. A visual comparative technique and surface roughness in the form of the Rq valuewere used to evaluate the surface appearance and the surface roughness respectively. The resultswere investigated statistically to find significant models. It was shown that high quality appearance,following a comparative scale, was possible using high die temperature and high injection speed. Itwas also found that improving the surface roughness will deteriorate the visual appearance.

  • 87.
    Jarfors, Anders
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Metal casting2014Inngår i: Handbook of Manufacturing Engineering and Technology / [ed] Andrew Y. C. Nee, London: Springer, 2014, s. 309-410Kapittel i bok, del av antologi (Fagfellevurdert)
  • 88.
    Jarfors, Anders
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Olofsson, Jakob
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Svensson, Ingvar L.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Critical Description of Defects and Mechanical Behaviour in Casting Process Modelling of Light Metals for Automotive Use2013Inngår i: Proceedings of the Twenty Second International Conference on Processing and Fabrication of Advanced Materials (PFAM-XXII), Singapore, 18-20 December, 2013, ACM Digital Library, 2013Konferansepaper (Fagfellevurdert)
  • 89.
    Jarfors, Anders
    et al.
    Royal Institute of technology.
    Svendsen, L
    Royal Institute of technology.
    Wallinder, M
    Royal Institute of technology.
    Fredriksson, H
    Royal Institute of technology.
    Reactions during infiltration of graphite fibres by molten Al-Ti alloy1993Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 24, nr 11, s. 2577-2583Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The infiltration sequence of graphite fibers with liquid aluminum alloyed with titanium was studied. The titanium concentration was chosen such that a severe reaction occurred between the fibers and the melt. Aluminum carbide and titanium carbide, as well as an aluminide phase were formed. The phenomenon occurring during the infiltration sequence was explained with the aid of the ternary-phase diagram Al-Ti-C. The effect of the reaction on the infiltration height is discussed.

  • 90. Jarfors, Björn
    et al.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ordbok - dictionary: svensk - English: tillverkningsteknik - manufacturing technology2018Bok (Annet vitenskapelig)
    Abstract [sv]

    Förord: Denna ordbok är framtagen för att underlätta studier inomTillverkningsteknologi och är ett samarbete mellan lärare och studenter inomMaskin och Materialteknik vid Jönköping University och Blekinge TekniskaHögskola.

  • 91.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ciavatta, Matteo
    University of Bologna, Bologna, Italy.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Svensson, Ingvar L.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Effect of Boron and Cross-Section Thickness on Microstructure and Mechanical Properties of Ductile Iron2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, s. 249-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Eeffect of Boron addition on the microstructure and mechanical properties of ductile iron, GJS-500-7 grade was studied. Three cast batches with the Boron content of 10, 49 and 131ppm were cast in a casting geometry containing plates with thicknesses of 7, 15, 30, 50 and 75mm. Microstructure analysis, tensile test, and hardness test were performed on the samples which were machined from the casting plates. Addition of 49 ppm Boron decreased pearlite fraction by an average of 34±6% in all the cast plates. However, minor changes were observed in the pearlite fraction by increasing Boron from 49 to 131 ppm. Variation in the plate thickness did not affect the pearlite fraction. The 0.2% offset yield and ultimate tensile strength was decreased by an average of 11±1% and 18±2%, respectively. Addition of 49 ppm Boron decreased Brinell hardness by 16±1%, while 11±2% reduction was obtained by addition of 131ppm Boron.

  • 92.
    Kasvayee, Keivan Amiri
    et al.
    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.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Development of a pattern making method for strain measurement on microstructural level in ferritic cast iron2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The current paper focuses on development of a method for studying micro-scale strains on the microstructure of ferritic cast iron. For this purpose, in-situ tensile tests were done under the optical microscope combined with digital image correlation (DIC). Critical in this development was to be able to achieve a reliable high spatial resolution of strain around microstructural features, such as graphite particles. Measurement of local strain fi elds in cast iron materials have so far been relying on displacement of naturally occurring microstructure patterns such as graphite particles, which limits the spatial resolution of strain measurement. In order to increase the spatial resolution of the measured strain, a pit etching procedure was applied to generate a random speckle pattern on the ferritic matrix. Th e critical challenges of in-situ investigation of microstructural deformation were identifi ed as speckle pattern quality and accurate selection of subset size and strain window size. Th e traceability of this method was studied by benchmarking the measured elastic modulus with that obtained from full-scale tensile test. Th e elastic modulus calculated from average strains, measured by DIC, showed a good agreement with material’s elastic modulus. Th is validates the measured localized strain values and can be used as a validation for modeling of local deformation.

  • 93.
    Kasvayee, Keivan Amiri
    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.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Micro-Crack Initiation in High-Silicon Cast Iron during Tension Loading2015Inngår i: TMS2015 Supplemental Proceedings, The Minerals, Metals, and Materials Society, 2015, John Wiley & Sons, 2015, s. 947-953Konferansepaper (Fagfellevurdert)
  • 94.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Microstructural strain distribution in ductile iron; Comparison between finite element simulation and digital image correlation measurements2015Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper presents a study on micro-scale deformation and the effect of microstructure on localised deformation of ductile iron, utilizing in-situ tension testing, digital image correlation (DIC) and finite element analysis (FEA). A tensile stage integrated with an optical microscope was used to acquire a series of micrographs during the tensile test. Applying DIC and an etched speckle pattern, a high resolution local strain field was measured in the microstructure. In addition, a finite element (FE) model was used to predict the strain maps. The materials parameters were optimized based on Ramberg-Osgood model. The DIC and simulation strain maps conformed to a large extent resulting in the verification of the model in micro-scale level. It was found that the Ramberg-Osgood theory can be used to capture the main trends of strain localization. The discrepancies between the simulated and DIC results were explained based on microstructure dimensionality, differences in spatial resolution and uncertainty in the FE-model.

  • 95.
    Kasvayee, Keivan Amiri
    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.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Jarfors, Anders E. W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Microstructural strain localization and crack evolution in ductile iron2015Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper focuses on the deformation and crack evolution in ductile iron under tension, investigated by coupled in-situ tensile test and finite element simulation. Micro-crack initiation and development were tracked at the microstructure level. The local strain around micro-cracks were measured by using Digital Image Correlation (DIC). The results obtained from the experiments were compared to a finite element  model including cohesive elements to enable crack propagation. The resulting local strains were analyzed in connection to the observed micro-crack incidents in both DIC and simulation. The predictions of the finite element model showed good agreement with those obtained from the experiment, in the case of early decohesion, the amplitude of the strain localization and macroscopic stress-strain behavior. The results revealed that decohesion was commonly initiated early around graphite surrounded by ferrite which was identified as high strain regions. By increasing the global deformation, micro-cracks initiated in these areas and propagated but were arrested within the ferrite zone due to strain hardening and stress shielding of pearlite. Both the DIC and the simulation revealed that irregular shaped graphite were more susceptible to strain localization and micro-crack initiation. It could be observed that the cohesive model was able to capture the main trends of localized plastic deformation and crack initiation

  • 96.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling.
    Sujakhu, S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Castagne, S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Strain localization and crack formation effects on stress-strain response of ductile iron2017Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 702, s. 265-271Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The strain localization and crack formation in ferritic-pearlitic ductile iron under tension was investigated by in-situ tensile tests. In-situ tensile tests under optical microscope were performed and the onset of the early ferrite-graphite decohesions and micro-cracks inside the matrix were studied. The results revealed that early ferrite-graphite decohesion and micro-cracks inside the ferrite were formed at the stress range of 280–330 MPa, where a kink occurred in the stress-strain response, suggesting the dissipation of energy in both plastic deformation and crack initiation. Some micro-cracks initiated and propagated inside the ferrite but were arrested within the ferrite zone before propagating in the pearlite. Digital Image Correlation (DIC) was used to measure local strains in the deformed micrographs obtained from the in-situ tensile test. Higher strain localization in the microstructure was measured for the areas in which the early ferrite-graphite decohesions occurred or the micro-cracks initiated.

  • 97.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Sujakhu, Surendra
    Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore.
    Castagne, Sylvie
    KU Leuven, Department of Mechanical Engineering, Leuven, Belgium.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Microstructural strain mapping during in-situ cyclic testing of ductile iron2018Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 140, s. 333-339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper focuses on local strain distribution in the microstructure of high silicon ductile iron during cyclic loading. In-situ cyclic test was performed on compact-tension (CT) samples inside the scanning electron microscope (SEM) to record the whole deformation and obtain micrographs for microstructural strain measurement by means of digital image correlation (DIC) technique. Focused ion beam (FIB) milling was used to generate speckle patterns necessary for DIC measurement. The equivalent Von Mises strain distribution was measured in the microstructure at the maximum applied load. The results revealed a heterogeneous strain distribution at the microstructural level with higher strain gradients close to the notch of the CT sample and accumulated strain bands between graphite particles. Local strain ahead of the early initiated micro-cracks was quantitatively measured, showing high strain localization, which decreased by moving away from the micro-crack tip. It could be observed that the peak of strain in the field of view was not necessarily located ahead of the micro-cracks tip which could be because of the (i) strain relaxation due to the presence of other micro-cracks and/or (ii) presence of subsurface microstructural features such as graphite particles that influenced the strain concentration on the surface.

    Fulltekst tilgjengelig fra 2020-04-12 00:00
  • 98.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Svensson, Ingvar L.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    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. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Characterization and modeling of the mechanical behavior of high silicon ductile iron2017Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 708, s. 159-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the effect of the solidification conditions and silicon content on the mechanical properties of ductile iron and presents empirical models for predicting the tensile behavior based on the microstructural characterizations. Two ductile iron grades of GJS-500-7 and GJS-500-14 were cast with silicon content of 2.36% and 3.71%, respectively. The cast geometry consisted of six plates with different thicknesses that provided different cooling rates during the solidification. Microstructure analysis, tensile and hardness tests were performed on the as-cast material. Tensile behavior was characterized by the Ludwigson equation. The tensile fracture surfaces were analyzed to quantify the fraction of porosity. The results showed that graphite content, graphite nodule count, ferrite fraction and yield strength were increased by increasing the silicon content. A higher silicon content resulted in lower work hardening exponent and strength coefficient on the Ludwigson equation. The results for 0.2% offset yield and the Ludwigson equation parameters were modeled based on microstructural characteristics, with influence of silicon content as the main contributing factor. The models were implemented into a casting process simulation to enable prediction of microstructure-based tensile behavior. A good agreement was obtained between measured and simulated tensile behavior, validating the predictions of simulation in cast components with similar microstructural characteristics.

  • 99.
    Kasvayee, Keivan Amiri
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Ghassemali, Ehsan
    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. Forskningsmiljö Material och tillverkning – Gjutning.
    Microstructural strain distribution in ductile iron: Comparison between finite element simulation and digital image correlation measurements2016Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 655, s. 27-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a study on microstructural deformation of a ferritic–pearlitic ductile iron, utilizing in-situ tensile testing, digital image correlation (DIC) and finite element analysis (FEA). For this purpose, the in-situ tensile test and DIC were used to measure local strain fields in the deformed microstructure. Furthermore, a continuum finite element (FE) model was used to predict the strain maps in the microstructure. Ferrite and pearlite parameters for the FE-model were optimized based on the Ramberg–Osgood relation. The DIC and simulation strain maps were compared qualitatively and quantitatively. Similar strain patterns containing shear bands in identical locations were observed in both strain maps. The average and localized strain values of the DIC and simulation conformed to a large extent. It was found that the Ramberg–Osgood model can be used to capture the main trends of strain localization. The discrepancies between the simulated and DIC results were explained based on the; (i) subsurface effect of the microstructure; (ii) differences in the strain spatial resolutions of the DIC and simulation and (iii) abrupt changes in strain prediction of the continuum FE-model in the interface of the phases due to the sudden changes in the elastic modulus.

  • 100.
    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.
    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.
    Castagne, S.
    Singapore Institute of Manufacturing Technology.
    Superplastic-like forming of non-superplastic AA5083 combined with mechanical pre-forming2011Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 52, nr 1-4, s. 123-129Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superplastic forming has been considered as an attractive process in the automotive and aerospace industries. However, the disadvantages of slow forming rate, high-temperature requirement, poor thickness distribution, and expensive base material have hindered its widespread use for high production volume. In this paper, the non-superplastic grade of 5083 aluminum alloy (AA5083) sheets with thickness of 3 mm was employed in a superplastic-like forming process, which is a combination of drawing (mechanical pre-forming) and superplastic forming (blow forming). Experimental trials were conducted to verify the possibility of improving the forming rate and lowering the process temperature. The blank was firstly pre-formed during the mechanical pre-forming phase. As a result, some part of material along the flange area was introduced inside the deformation cavity in advance of the blow forming phase. Secondly, argon gas was applied on the sheet, which would be deformed to come into contact with the inner die surface at the end of pressure cycle. It took only 8 min for the blow forming phase, and the process achieved an almost fully formed part at 400°C. The minimum thickness occurred at the inward corners, and the maximum thinning of the formed part was 54%. Grain growth and cavitation were found from the microstructure observations.

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