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  • 251.
    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.

  • 252.
    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.

  • 253.
    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.

  • 254.
    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.

  • 255.
    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.

  • 256.
    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.

  • 257.
    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.

  • 258.
    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.

  • 259.
    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.

  • 260.
    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.

  • 261.
    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))
  • 262.
    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.

  • 263.
    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)
  • 264.
    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)
  • 265.
    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)
  • 266.
    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.

  • 267.
    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.

  • 268.
    Jarfors, Anders E.W.
    et al.
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    Du, Andong
    China Academy of Machinery Sciences and Technology (Jiangle), Institute of Semi-solid Metal Technology, Sanming City, China.
    Yu, Gegan
    China Academy of Machinery Sciences and Technology (Jiangle), Institute of Semi-solid Metal Technology, Sanming City, China.
    Zheng, Jinchuan
    China Academy of Machinery Sciences and Technology (Jiangle), Institute of Semi-solid Metal Technology, Sanming City, China.
    Wang, Kaikun
    University of Science and Technology Beijing, School of Materials Science and Engineering, Department of Materials Processing and Control Engineering, Beijing, China.
    On the sustainable choice of alloying elements for strength of aluminum-based alloys2020Inngår i: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 12, nr 3, artikkel-id 1059Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aluminum alloys are today entirely recyclable and are seen as a sustainable material. However, there are limitations in the use of aluminum from material strength and cost perspective. Nickel, copper and rare earth metals are alloying elements that may provide strength at room and elevated temperatures. These are, however, often seen as harmful from a sustainability viewpoint. Additionally, these alloying elements are commonly costly. The current paper makes an analysis of the sustainability-strength dimension of alloying, together with a cost perspective, to guide alloy producers and alloy users in making an educated choice of direction for future materials and material development.

  • 269.
    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.

  • 270.
    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.

  • 271.
    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.

  • 272.
    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)
  • 273.
    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)
  • 274.
    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.

  • 275.
    Johansson, J.
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Belov, I.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Johnson, E.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    An approach to life consumption monitoring of solder joints in operating temperature environment2012Inngår i: Proceedings of 13th IEEE International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2012, Cascais, Portugal, April 16-17-18, 2012, IEEE, 2012, s. -8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper elaborates the 3T-approach to life consumption monitoring of solder joints in operating temperature environment without requiring simplification of operating loads. An overview of the 3T-approach is provided including assumptions made for a proposed realization in an avionic application. Associated implementation routines are highlighted and exemplified for a lead-free PBGA256 package with creep strain energy density (SEDcr) as damage metric. Factors that affect the prediction accuracy are investigated. A data resolution has been determined that delivers response surfaces that provide results comparable to 3-D finite-element (FE) simulations, while bearing two orders of magnitude higher computational efficiency. A stress-free temperature modification routine is proposed and proves to further mitigate accuracy problems.

  • 276.
    Johansson, Jonas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Belov, Ilja
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Johnson, Erland
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Dudek, Rainer
    Fraunhofer ENAS, Micro Materials Center, Chemnitz, Germany.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Investigation on thermal fatigue of SnAgCu, Sn100C, and SnPbAg solder joints in varying temperature environments2014Inngår i: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 54, nr 11, s. 2523-2535Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal cycling tests have been performed for a range of electronic components intended for avionic applications, assembled with SAC305, SN100C and SnPbAg solder alloys. Two temperature profiles have been used, the first ranging between −20 °C and +80 °C (TC1), and the second between −55 °C and +125 °C (TC2). High level of detail is provided for the solder alloy composition and the component package dimensions, and statistical analysis, partially supported by FE modeling, is reported. The test results confirm the feasibility of SAC305 as a replacement for SnPbAg under relatively benign thermomechanical loads. Furthermore, the test results serve as a starting point for estimation of damage accumulation in a critical solder joint in field conditions, with increased accuracy by avoiding data reduction. A computationally efficient method that was earlier introduced by the authors and tested on relatively mild temperature environments has been significantly improved to become applicable on extended temperature range, and it has been applied to a PBGA256 component with SAC305 solder in TC1 conditions. The method, which utilizes interpolated response surfaces generated by finite element modeling, extends the range of techniques that can be employed in the design phase to predict thermal fatigue of solder joints under field temperature conditions.

  • 277.
    Johansson, Jonas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Electronic Defence Systems, Saab AB, Jönköping, Sweden.
    Belov, Ilja
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Johnson, Erland
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. SP Technical Research Institute of Sweden, Borås, Sweden.
    A computational method for evaluating the damage in a solder joint of an electronic package subjected to thermal loads2014Inngår i: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 31, nr 3, s. 467-489Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose – The purpose of this paper is to introduce a novel computational method to evaluate damage accumulation in a solder joint of an electronic package, when exposed to operating temperature environment. A procedure to implement the method is suggested, and a discussion of the method and its possible applications is provided in the paper.

    Design/methodology/approach – Methodologically, interpolated response surfaces based on specially designed finite element (FE) simulation runs, are employed to compute a damage metric at regular time intervals of an operating temperature profile. The developed method has been evaluated on a finite-element model of a lead-free PBGA256 package, and accumulated creep strain energy density has been chosen as damage metric.

    Findings – The method has proven to be two orders of magnitude more computationally efficient compared to FE simulation. A general agreement within 3 percent has been found between the results predicted with the new method, and FE simulations when tested on a number of temperature profiles from an avionic application. The solder joint temperature ranges between +25 and +75°C.

    Practical implications – The method can be implemented as part of reliability assessment of electronic packages in the design phase.

    Originality/value – The method enables increased accuracy in thermal fatigue life prediction of solder joints. Combined with other failure mechanisms, it may contribute to the accuracy of reliability assessment of electronic packages.

  • 278.
    Johansson, Jonas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Method for Prognostics of Thermal Fatigue Failure of Solder Joints in Avionic Equipment2008Konferansepaper (Annet vitenskapelig)
  • 279.
    Johansson, Jonas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Prognostics of Thermal Fatigue Failure of Solder Joints in Avionic Equipment2012Inngår i: IEEE Aerospace and Electronic Systems Magazine, ISSN 0885-8985, E-ISSN 1557-959X, Vol. 27, nr 4, s. 16-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A practical method has been suggested for solder joint thermal fatigue prognostics, which enables real-time fatigue calculations based on uncompressed temperature data embedded in a host system that performs safety-critical operations. The accuracy of the prognosticated remaining useful life depends on the level of details captured in the model, and the level of confidence from validation efforts.

  • 280.
    Jones, C. A.
    et al.
    Sustainable Manufacturing System Centre, Cranfield University, Bedfordshire, United Kingdom.
    Jolly, M. R.
    Sustainable Manufacturing System Centre, Cranfield University, Bedfordshire, United Kingdom.
    Jarfors, Anders E.W.
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    Irwin, M.
    TPC Components AB, Hallstahammer, Sweden.
    An experimental characterization of thermophysical properties of a porous ceramic shell used in the investment casting process2020Inngår i: TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings / [ed] Z. Peng, J.-Y. Hwang, J. Downey, D. Gregurek, B. Zhao, O. Yucel, E. Keskinkilic, T. Jiang, J. White, & M. Mahmoud, Springer, 2020, s. 1095-1105Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study presents the results of an investigation that characterises the thermophysical properties of an investment casting mould, comprising of a Zirconium dioxide/Cobalt aluminate prime slurry and a fused Silica/fibre reinforced backup slurry. Growing prevalence of successful computer simulations within the foundry industry enables defects that emerge during the casting process to become increasingly predictable, providing cost-effective alternatives to trial castings. The viability of these simulations as predictors is heavily dependent upon the facilitation of accurate material property data, as attained through this investigation. Differential scanning calorimetry (DSC) and laser flash analysis (LFA) were utilized to determine the specific heat capacity and thermal diffusivity, respectively. These values, in combination with the material density and linear coefficient of thermal expansion, have been used to determine the thermal conductivity of the mould. With the aim of verifying these parameters, initial studies in Flow-3D® simulation software have been performed to determine the constraints needed to reduce variability in simulation parameters. Due to the diversity of casting moulds used throughout the industry, ensuring the material database is kept as comprehensively populated as possible is a crucial undertaking. 

  • 281.
    Jönsson, Pär
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Aune, Ragnhild E.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Du, Sichen
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Teng, Lidong
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Matsushita, Taishi
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Sundberg, Sven
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    The seetharaman seminar june 14-15, 2010 in stockholm, Sweden2012Inngår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 31, nr 3, s. 193-193Artikkel i tidsskrift (Annet vitenskapelig)
  • 282. Kappey, Jens
    et al.
    Schneider, Marc
    Svensson, Ingvar
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Sjölander, Emma
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Seifeddine, Salem
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Shahid, Akhtar
    Arnberg, Lars
    Microstructure, Defects and Properties in Aluminium Alloy Castings: Modelling and Simulation2010Inngår i: : Advanced methods for industrial engineering, 2010Konferansepaper (Annet vitenskapelig)
  • 283.
    Kasap, Yücel
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Optimization of the Chemical Analysis SS-EN-GJL-250 Using Casting Simulation Software2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main purpose of the thesis work is based on achieving same mechanical properties on the three different sized bearing housings. The key mechanical property that had to be focused on was the hardness of the parts. In order to achieve this goal, chemical compositions of the parts have studied. However there were some limitations on the composition variants. Allowed variables of the compositions are silicon, nickel and copper. Due to necessity another element, Molybdenum (Mo), was also introduced. After many simulations three different compositions are proposed. Then the feasibility of results of casting simulation software investigated. And finally an optimization guideline has proposed. Chemical composition researches have carried on casting simulation software, which is called Magma5. Following the completion of the simulations phase, proposed compositions trial casted at the company. Subsequent to trial castings cast parts had tested for their hardness values. In order to bring the thesis to completion simulation outputs and trial test results had compared. With the help of a casting simulation software composition optimisation of different sized parts could be easily optimised in order to achieve same results. Many simulations are executed with different composition for the silicon, nickel, copper and molybdenum variants. It was seen that Mo additions significantly increase the mechanical properties of the parts. Nickel and copperacts similarly on the hardness values, however nickel addition reduce undercooling tendency at a greater rate. Good inoculation is vital for the parts with thin sections. Decent inoculation helps to improve the microstructure and helps to get closer results tothe simulated values. However software represents key information aboutundercooled zones on the part. Software ensures 95% to 97% correct values on hardness results.

  • 284.
    Kasvayee, Keivan Amiri
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Microstructure and deformation behaviour of ductile iron under tensile loading2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The current thesis focuses on the deformation behaviour and strain distribution in the microstructure of ductile iron during tensile loading. Utilizing Digital Image Correlation (DIC) and in-situ tensile test under optical microscope, a method was developed to measure high resolution strain in microstructural constitutes. In this method, a pit etching procedure was applied to generate a random speckle pattern for DIC measurement. The method was validated by benchmarking the measured properties with the material’s standard properties.

    Using DIC, strain maps in the microstructure of the ductile iron were measured, which showed a high level of heterogeneity even during elastic deformation. The early micro-cracks were initiated around graphite particles, where the highest amount of local strain was detected. Local strain at the onset of the micro-cracks were measured. It was observed that the micro-cracks were initiated above a threshold strain level, but with a large variation in the overall strain.

    A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The materials parameters for this model were calculated by optimization, utilizing Ramberg-Osgood equation. For benchmarking, the predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. The DIC and simulation strain maps conformed to a large extent resulting in the validation of the model in micro-scale level.

    Furthermore, the results obtained from the in-situ tensile test were compared to a FE-model which compromised cohesive elements to enable cracking. The stress-strain curve prediction of the FE simulation showed a good agreement with the stress-strain curve that was measured from the experiment. The cohesive model was able to accurately capture the main trends of microscale deformation such as localized elastic and plastic deformation and micro-crack initiation and propagation.

  • 285.
    Kasvayee, Keivan Amiri
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    On the deformation behavior and cracking of ductile iron; effect of microstructure2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis focuses on the effect of microstructural variation on the mechanical properties and deformation behavior of ductile iron. To research and determine these effects, two grades of ductile iron, (i) GJS-500-7 and (ii) high silicon GJS-500-14, were cast in a geometry containing several plates with different section thicknesses in order to produce microstructural variation. Microstructural investigations as well as tensile and hardness tests were performed on the casting plates. The results revealed higher ferrite fraction, graphite particle count, and yield strength in the high silicon GJS-500-14 grade compared to the GJS-500-7 grade.

    To study the relationship between the microstructural variation and tensile behavior on macroscale, tensile stress-strain response was characterized using the Ludwigson equation. The obtained tensile properties were modeled, based on the microstructural characteristics, using multiple linear regression and analysis of variance (ANOVA). The models showed that silicon content, graphite particle count, ferrite fraction, and fraction of porosity are the major contributing factors that influence tensile behavior. The models were entered into a casting process simulation software, and the simulated microstructure and tensile properties were validated using the experimental data. This enabled the opportunity to predict tensile properties of cast components with similar microstructural characteristics.

    To investigate deformation behavior on micro-scale, a method was developed to quantitatively measure strain in the microstructure, utilizing the digital image correlation (DIC) technique together with in-situ tensile testing. In this method, a pit-etching procedure was developed to generate a random speckle pattern, enabling DIC strain measurement to be conducted in the matrix and the area between the graphite particles. The method was validated by benchmarking the measured yield strength with the material’s standard yield strength.

    The microstructural deformation behavior under tensile loading was characterized. During elastic deformation, strain mapping revealed a heterogeneous strain distribution in the microstructure, as well as shear bands that formed between graphite particles. The crack was initiated at the stress ranges in which a kink occurred in the tensile curve, indicating the dissipation of energy during both plastic deformation and crack initiation. A large amount of strain localization was measured at the onset of the micro-cracks on the strain maps. The micro-cracks were initiated at local strain levels higher than 2%, suggesting a threshold level of strain required for micro-crack initiation.

    A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The material parameters for this model were calculated by optimization, utilizing the Ramberg-Osgood equation. The predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. To a large extent, the strain maps were in agreement, resulting in the validation of the model on micro-scale.

    In order to perform a micro-scale characterization of dynamic deformation behavior, local strain distribution on the microstructure was studied by performing in-situ cyclic tests using a scanning electron microscope (SEM). A novel method, based on the focused ion beam (FIB) milling, was developed to generate a speckle pattern on the microstructure of the ferritic ductile iron (GJS-500-14 grade) to enable quantitative DIC strain measurement to be performed. The results showed that the maximum strain concentration occurred in the vicinity of the micro-cracks, particularly ahead of the micro-crack tip.

  • 286.
    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.

  • 287.
    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.

  • 288.
    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)
  • 289.
    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.

  • 290.
    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

  • 291.
    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.

  • 292.
    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
  • 293.
    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.

  • 294.
    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.

  • 295.
    Kermanpur, A.
    et al.
    Department of Materials Engineering, Isfahan University of Technology.
    Ghassemali, Ehsan
    tment of Materials Engineering, Isfahan University of Technology.
    Salemizadeh, S.
    tment of Materials Engineering, Isfahan University of Technology.
    Synthesis and characterisation of microporous titania membranes by dip-coating of anodised alumina substrates using sol–gel method2008Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 461, nr 1-2, s. 331-335Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to synthesis microporous titania membranes by dip-coating of symmetric mesoporous anodised alumina substrates using sol–gel method. A stable titania sol containing nanoparticles was first prepared by establishing the proper values of the acid/alkoxide and the water/alkoxide molar ratios and pH. The titania sol was then utilised to dip-coat the anodised alumina substrates. The effects of dipping time, withdrawal rate, and sintering temperature were studied for both single- and double-layer coated samples. The thickness, structure and phase analysis of the coated membranes were characterised using thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. The process conditions to achieve uniform, microporous titania coatings on the mesoporous alumina substrates were proposed.

  • 296.
    Kukadiya, Heena
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Heat Transfer in Aluminium Coils under Annealing Condition2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Abstract 

    This report contains an investigation of the annealing process of an aluminium coil in industrial furnace environment. The main result of this investigation is a predictive FE simulation model within adequate accuracy which aids in annealing process design.

    The procedure starts with a literature study of both the key parameters in general and the modelling and experimental methods related to heat transfer in industrial coils. Additional CAE tools are identified to support the research.

    The procedure follows the implementation of the existing radial thermal conductivity model in a FE simulation, for different coil thicknesses and winding forces. The measured strip surface roughness and the crowning slope serve as input parameters in the effective radial thermal conductivity model.

    Furthermore, the effective heat transfer coefficient models for coil sides have been developed and calibrated. Both the radial thermal conductivity and convective heat transfer models are integrated in the FE model of the coil annealing process.

    The coil annealing experiments have been conducted in an industrial furnace at Gränges AB. The experimental data support the creation and validation of the FE simulation model.

    The simulation-based parametric study evaluates the importance of considering the relevant physical phenomena in the model.

    The FE model of the annealing process has been validated against the temperature measurements within 10% at the target material temperature. The model can be applied for coil temperature predictions as part of the annealing process design.

    The overall method generates engineering guidelines to design the annealing process with the help of simulation tools.

  • 297.
    Kus, Ömer
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Mojtabavi, Hamed
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Redesign of a Shock Absorber Piston Using Sintering2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main objective of this report is to re-design of a product by substituting for another manufacturing process in order to get a cheaper product with the same function and quality. The current shock absorber piston is manufactured by the machining process at Öhlins Racing AB Company. Power Metallurgy (P/M) method could be a good substitute process to meet the technical requirements of the current piston with total lower cost. In this case, the whole process of product development gets involved in designing two new pistons from base-design to final product. One design is assigned to a cheaper P/M process as called Conventional Press and Sinter. Another P/M process as called Metal Injection Molding (MIM) is considered to produce the more expensive piston. According to the design guidelines of P/M processes, the base pistons are modelled in a three dimensional environment, and then an appropriate powder metal is selected for each. Consequently, the next stage is to analyse the piston strengths by Finite Element Method under the static and dynamic loadings. Fatigue analysis is taken into consideration for the cyclic loadings, and the static strength can be assessed for the static loading mode. The results show the infinite fatigue life for two different designs, and no plastic deformation is observed during analysing of the pistons under static loading. Cost estimation is the last stage of this master thesis. Compared to the total costs for the current design, the total estimations for the whole final P/M products can prove the significant drop in the final prise for each design. Thus, environmental and financial issues are already met in achieving the new pistons in this project by saving considerably money and energy. On-going stages will be to make prototype and get them tested under the real working conditions in respect to the standards.

  • 298.
    Kwapisz, Krzysztof
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Gwóźdź, Marcin
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Maskinteknik.
    Influence of ageing process on the microstructure and mechanical properties of aluminium-silicon cast alloys - Al-9%Si-3%Cu and Al-9%Si-0.4%Mg2008Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The aim of this thesis is to investigate the influence of ageing process on the microstructure and mechanical properties of aluminium-silicon alloys. The investigation was carried on Al-9%Si-3%Cu and Al-9%Si-0.4%Mg. To obtain different DAS with low content of oxide films and micro shrinkage, gradient solidification has been used. The specimens were treated according to T6 heat treatment.

    In this thesis it has been shown that solidification rate has great influence on mechanical properties since it controls microstructure. To reach peak level of mechanical properties different times of artificial ageing were used depending on the alloy.

    In peak value condition Yield’s Strength of alloys was 197MPa for Al-Si-Cu alloy and 243MPa for Al-Si-Mg one. These results can be compared to these presented in other papers concerning aluminium silicon alloys. Such comparison shows that when talking about potential of alloy, these results are more or less the same as in other articles in this field.

    The work was conducted within 10 weeks and for this reason not all the necessary data was collected. Further work will be conducted to obtain missing results, like overaged state for Al-Si-Cu alloy.

  • 299.
    Lang, Jenny
    et al.
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Belov, Ilja
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Hellén, Johan
    Saab AB, Gothenburg, Sweden.
    Lim, Jang-Kwon
    Acreo Swedish ICT, Kista, Sweden.
    Schodt, Bo
    SP Technical Research Institute of Sweden, Copenhagen, Denmark.
    Nilsson, Torbjörn M. J.
    Saab AB, Gothenburg, Sweden.
    Poder, Ralf
    SP Technical Research Institute of Sweden, Copenhagen, Denmark.
    Bakowski, Mietek
    Acreo Swedish ICT, Kista, Sweden.
    Leisner, Peter
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Thermo-mechanical Reliability and Performance Degradation of a Lead-free RF Power Amplifier with GaN-on-SiC HEMTs2016Inngår i: Proceedings of the 11th European Conference on Silicon Carbide and Related Materials (ECSCRM), IEEE, 2016, nr 12Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objects under investigation in this study are RF-transistors, solder joint materials and thermal interface materials (TIM). In total 50 RF power amplifier demonstrators consisting each of a PCB board containing one GaN-on-SiC, HEMT, CHZ015A-QEG, from UMS in SMD quad-flat no-leads package (QFN) were assembled for the study. Two types of lead-free solders (Sn63Pb36Ag2 and SnAgCu (SAC305)) and two types of TIM materials (NanoTIM and TgonTM 805) for PCB attachment to liquid cold plate were tested for thermo-mechanical reliability. The demonstrators were subjected to thermal cycles (TC) and power cycles (PC) and evaluated electrically, thermally and structurally. A set of 24 demonstrators were subjected to thermal stress by 2300 thermal cycles (TC) between -20°C and 80°C and remaining 26 demonstrators were subjected to the electrical stress by power cycling (PC) with a drain current of 100 mA at a drain voltage of 45 V and a cycle time of 2 min. High-frequency (HF) characterization of all the boards was done before exposure to the thermal and electrical stresses. Static electrical characterization of all the devices was performed by measuring threshold voltage and blocking voltage and output characteristics. The static electrical and HF characterization was repeated after 2300 thermal cycles and after 1100, 4700 and 14500 power cycles. In addition, the packages were inspected by optical microscopy and by 2D-Xray microscopy, in order to reveal possible failures in solder joints. The main reason for the thermal cycling tests was to test the solder joint reliability. The suggested tests were based on standard IPC 785, treating HEMT devices and solder. One thermal cycle took 113 min. One month of the accelerated test is equal to about one year use in field conditions. The rampup slope was 2-3°C/min and the dwell time was 15 min. The temperature in the chamber and the temperature on at least one board were recorded during the whole test.

    The main reason for the power cycling tests was to investigate degradation of the transistor package and TIM, including the die during cyclic heating and cooling. The temperature distribution on the HEMT package and PCB was measured, several times during the test by thermal imaging and by thermocouples. Power cycling was performed at room temperature with demonstrator boards mounted on a liquid cold plate. The power cycling implies DC-test with on/off sections where the demonstrators reach steady state in-between. The cycle time was set to 2 min. The boards were ID labeled and underwent a screening procedure under which some were visually inspected, powered up and investigated with X-ray. After finishing TC and PC tests selected boards were visually inspected in white light, X-rayed and a couple of boards were subjected to cross-section investigations for failure analysis.

  • 300.
    Lang, Jenny
    et al.
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Belov, Ilja
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Hellén, Johan
    Saab AB, Gothenburg, Sweden.
    Lim, Jang-Kwon
    Acreo Swedish ICT, Kista, Sweden.
    Schodt, Bo
    SP Technical Research Institute of Sweden, Copenhagen, Denmark.
    Nilsson, Torbjörn M. J.
    Saab AB, Gothenburg, Sweden.
    Poder, Ralf
    SP Technical Research Institute of Sweden, Copenhagen, Denmark.
    Bakowski, Mietek
    Acreo Swedish ICT, Kista, Sweden.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Thermo-mechanical reliability and performance degradation of a lead-free RF power amplifier with GaN-on-SiC HEMTs2017Inngår i: Materials Science Forum, Trans Tech Publications, 2017, Vol. 897, s. 715-718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    RF power amplifier demonstrators containing each one GaN-on-SiC, HEMT, CHZ015AQEG, from UMS in SMD quad-flat no-leads package (QFN) were subjected to thermal cycles (TC) and power cycles (PC) followed by electrical, thermal and structural evaluation. Two types of solders i.e. Sn63Pb36Ag2 and lead-free SnAgCu (SAC305) and two types of TIM materials (NanoTIM and TgonTM 805) for PCB attachment to liquid cold plate were tested for thermomechanical reliability. Changes in electrical performance of the devices namely reduction of the current saturation value, threshold voltage shift, increase of the leakage current and degradation of the HF performance were observed as a result of an accumulated current stress during PC. No significant changes in the investigated solder or TIM materials were observed.

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