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1.	Azizov, Talyat, et al. (författare) Consideration of the Torsional Stiffness in Hollow-Core Slabs’ Design 2019 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 968, s. 330-341 Tidskriftsartikel (refereegranskat)abstract The paper discusses the principles of precast concrete hollow-core slabs taking into account their spatial work. It is shown that consideration of spatial work makes it possible to determine the forces in individual floor slabs significantly more precise. The fact that strain redistribution between precast floor slabs depends on slabs’ bending and torsional stiffness is shown. The research has been mostly devoted to the determination of the bending stiffness with regard to the formation of cracks and the change in torsional stiffness, especially considering the presence of normal cracks, which is still unstudied. This paper presents the technique for determining the torsional stiffness of hollow-core slabs with normal cracks. In order to determine the components included in the resolving system of equations, it is proposed to use an approximation method based on the processing of numerical data using spatial finite elements.
2.	Badger, J., et al. (författare) Grinding of cermets with cup-wheels 2016 Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. - 9783035710342 ; 874, s. 115-123 Konferensbidrag (refereegranskat)abstract Cup-wheels are frequently used to grind cermets, a difficult-to-grind material. An investigation was made into the transient geometry of the cup-wheel rim, grit dulling, wheel loading, and wheel self-sharpening with chip thickness. Tests were performed on a saw-tip grinding machine and specific energies, G-ratios and rim geometries were measured. Results showed that, like grinding of tungsten-carbide, loading is prevalent. However, unlike grinding of tungstencarbide, grit dulling is also prevalent and wheel conditioning is of limited use. Much better results, particularly with respect to surface finish, can be obtained if the wheel is trued to a predetermined geometry. In addition, grinding parameters must be chosen to induce wheel self-sharpening. Practical recommendations are given.
3.	Chudinova, Ekaterina, et al. (författare) In Vitro Assessment of Hydroxyapatite Coating on the Surface of Additive Manufactured Ti6Al4V Scaffolds 2017 Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 879, s. 2444-2449 Tidskriftsartikel (refereegranskat)abstract Custom orthopedic and dental implants may be fabricated by additive manufacturing (AM), for example using electron beam melting technology. This study is focused on the modification of the surface of Ti6Al4V alloy coin-like scaffolds fabricated via AM technology (EBM®) by radio frequency (RF) magnetron sputter deposition of hydroxyapatite (HA) coating. The scaffolds with HA coating were characterized by Scanning Electron microscopy, X-ray diffraction. HA coating showed a nanocrystalline structure with the crystallites of an average size of 32±9 nm. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells was studied using biological short-term tests in vitro. In according to in vitro assessment, thin HA coating stimulated the attachment and proliferation of cells. Human mesenchymal stem cells cultured on the HA-coated scaffold also formed mineralized nodules.
4.	Domeij, Björn, 1988-, et al. (författare) Solidification Chronology of the Metal Matrix and a Study of Conditions for Micropore Formation in Cast Irons Using EPMA and FTA 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 436-443 Tidskriftsartikel (refereegranskat)abstract Microsegregation is intimately coupled with solidification, the development of microstructure, and involved in the formation of various casting defects. This paper demonstrates how the local composition of the metal matrix of graphitic cast irons, measured using quantitative electron microprobe analysis, can be used to determine its solidification chronology. The method is applied in combination with Fourier thermal analysis to investigate the formation of micropores in cast irons with varying proportions of compacted and spheroidal graphite produced by remelting. The results indicate that micropores formed at mass fractions of solid between 0.77 and 0.91, which corresponded to a stage of solidification when the temperature decline of the castings was large and increasing. In 4 out of the 5 castings, pores appear to have formed soon after the rate of solidification and heat dissipation had reached their maximum and were decreasing. While the freezing point depression due to build-up of microsegregation and the transition from compacted to spheroidal type growth of the eutectic both influencing solidification kinetics and the temperature evolution of the casting, the results did not indicate a clear relation to the observed late deceleration of solidification.
5.	Elahipanah, Hossein, et al. (författare) 4.5-kV 20-mΩ. cm2 Implantation-Free 4H-SiC BJT with Trench Structures on the Junction Termination Extension 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. - 9783038354789 ; 821, s. 838-841 Tidskriftsartikel (refereegranskat)abstract A single-mask junction termination extension withtrench structures is formed to realize a 4.5 kV implantation-free 4H-SiCbipolar junction transistor (BJT). The trench structures are formed on the baselayer with dry etching using a single mask. The electric field distributionalong the structure is controlled by the number and dimensions of the trenches.The electric field is distributed by the trench structures and thus the electricfield crowding at the base and mesa edges is diminished. The design isoptimized in terms of the depth, width, spacing, and number of the trenches toachieve a breakdown voltage (VB) of 4.5 kV, which is 85% of thetheoretical value. Higher efficiency is obtainable with finer lithographicresolution leading to smaller pitch, and higher number and narrower trenches.The specific on-resistance (RON) of 20 mΩ.cm2 is measuredfor the small-area BJT with active area of 0.04 mm2. The BV-RONof the fabricated device is very close to the SiC limit and by far exceeds thebest SiC MOSFETs.
6.	Elahipanah, Hossein, 1982-, et al. (författare) Modification of Etched Junction Termination Extension for the High Voltage 4H-SiC Power Devices 2016 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 858, s. 978-981 Tidskriftsartikel (populärvet., debatt m.m.)abstract High voltage 4H-SiC bipolar junction transistors (BJTs) with modified etched junction termination extension (JTE) are fabricated and optimized in terms of the length and remaining dose of JTEs. It is found that the JTE1 is the most effective one in spreading the electric field. Hence, for a given total termination length, a decremental JTE length from the innermost edge to the outermost mesa edge of the device results in better modification of the electric field. A breakdown voltage of 4.95 kV is measured for the modified device, which shows ~20% improvement of the termination efficiency for no extra cost or extra process step. Equal-size BJTs by interdigitated-emitter with different number of fingers and cell pitches are fabricated. It is presented that the maximum current gain decreases by having more fingers while the maximum current gain is achieved at higher current density.
7.	Eriksson, Jens, et al. (författare) Modified Epitaxial Graphene on SiC for Extremely Sensitive andSelective Gas Sensors 2016 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 858, s. 1145-1148 Tidskriftsartikel (refereegranskat)abstract Two-dimensional materials offer a unique platform for sensing where extremely high sensitivity is a priority, since even minimal chemical interaction causes noticeable changes inelectrical conductivity, which can be used for the sensor readout. However, the sensitivity has to becomplemented with selectivity, and, for many applications, improved response- and recovery times are needed. This has been addressed, for example, by combining graphene (for sensitivity) with metal/oxides (for selectivity) nanoparticles (NP). On the other hand, functionalization or modification of the graphene often results in poor reproducibility. In this study, we investigate thegas sensing performance of epitaxial graphene on SiC (EG/SiC) decorated with nanostructured metallic layers as well as metal-oxide nanoparticles deposited using scalable thin-film depositiontechniques, like hollow-cathode pulsed plasma sputtering. Under the right modification conditions the electronic properties of the surface remain those of graphene, while the surface chemistry can betuned to improve sensitivity, selectivity and speed of response to several gases relevant for airquality monitoring and control, such as nitrogen dioxide, benzene, and formaldehyde.
8.	Forouzan, Farnoosh, 1985-, et al. (författare) Effect of tempering on microstructure and mechanical properties of laser welded and post-weld treated AHSS specimens 2017 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 891, s. 18-24 Tidskriftsartikel (refereegranskat)abstract An advanced high strength steel (0.08 wt.%C, 1.79 wt%Mn, 0.23 wt%Si) was subjected to different post-weld heat treatments by quenching & tempering treatments (Q&T) after laser welding to reduce the risk of martensite formation in a few seconds based on an idea of quench and partitioning (Q&P), mechanism. The thermal stability of retained austenite, microstructure development and mechanical properties have been studied at 2 tempering temperatures of 440°C (Ms) and 636°C (Bs), both for 15 minutes, by means of electron microscopy, dilatometry, hardness profile and tensile tests. Dilatometer study unveiled that redistribution of carbon atoms and precipitation of transition carbides occur around 150°C and austenite decomposition occur at 600°C. Tempering at 636°C resulted in notable effect on the mechanical properties, while no significant difference was detected at 440°C, except a slight hardness drop. The strength increased up to 12% for the different specimens without significant loss in ductility for all specimens tempered at 636°C, which may be caused by precipitation hardening and recrystallization of martensite lath boundaries during tempering around 600°C.
9.	Fourlakidis, Vasilios, et al. (författare) Strength prediction of lamellar graphite iron : From Griffith’s to hall-petch modified equation 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; , s. 272-279 Konferensbidrag (refereegranskat)abstract Traditionally, ultimate tensile strength (UTS) is used as the main property for the characterization of lamellar graphite iron (LGI) alloys under static loads. The main models found in the literature for predicting UTS of pearlitic lamellar graphite iron are based on either regression analysis on experimental data or on modified Griffith or Hall-Petch equation. In pearlitic lamellar graphite iron the primary austenite dendritic network, transformed to pearlite, reinforces the bulk material while the distance between those pearlite grains, defines the maximum continuous defect size in the bulk material. Recently the novel parameter of the Diameter of Interdendritic Space has been used to express the flow length in a modified Griffith equation for the prediction of the UTS in LGI. Nevertheless this model neglects the strengthening effect of the pearlite lamellar spacing within the perlite grains. A model based on modified Hall-Petch equation was developed in this work. The model considers the effect of both microstructure parameters and covers a broad spectrum of microstructure sizes typical for complex shape castings with various wall thicknesses.
10.	Ghasemi, Rohollah, 1983-, et al. (författare) Scratch behaviour of silicon solid solution strengthened ferritic compacted graphite iron (CGI) 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 318-325 Tidskriftsartikel (refereegranskat)abstract The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal load conditions. Matrix solution hardening was made by alloying with different contents of Si; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance were observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys.
11.	Gyhlesten Back, Jessica, et al. (författare) Influence of prior deformation in austenite on the martensite formation in a low-alloyed carbon steel 2019 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 941, s. 95-99 Tidskriftsartikel (refereegranskat)abstract The current work aims at developing models supporting design of the rolling and quenching processes. This requires a martensite formation model that can account for effect of previous plastic deformation as well as evolution of stress and temperature during the quenching step. The effect of deformation prior to the cooling on the transformation is evaluated. The experimental result shows that prior deformation impedes the martensite transformation due to the mechanical stabilisation of the austenite phase. Larger deformation above 30 % reduces the effect of the mechanical stabilisation due to increase in martensite nucleation sites. The computed transformation curves, based on an extended version of the Koistinen-Marburger equation, agree well with experimental results for pre-straining less than 30 %.
12.	Hammersberg, Peter, 1961, et al. (författare) Variation of tensile properties of high silicon ductile iron 2018 Ingår i: Mater. Sci. Forum. - 9783035710557 ; 925 MSF, s. 280-287 Konferensbidrag (refereegranskat)abstract The casting processes are characterized by complex relationships between predictors and responses. It is the fundamental understanding of these complex relationships that often involves hundreds of factors, which improves quality without losing productivity and raising cost. In this work, cast solid solution strengthened ferritic spheroidal graphite irons GJS-500-14 and GJS-600-10 (EN 1563:2012) have been evaluated. These materials offer stronger components with good machinability owing to their even hardness properties. In this case the predictors are chemical composition, gating layout, foundry set-up, testing procedure and equipment etc. and the responses are the tensile properties (Rp0.2, Rm, A5). Here 200 tensile specimens compiled from industrial foundry melts from over 30 years of research have created a state-of-the-art platform for statistical engineering in order to perform Exploratory Data Analysis (EDA) and data visualization. This statistical platform has provided new insight on how foundries should treat complex relationships between predictors and responses in order to identify sources of variation and interaction effects.
13.	Hedayati, Raheleh, 1984-, et al. (författare) High Temperature Bipolar Master-Slave Comparator and Frequency Divider in 4H-SiC Technology 2017 Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 897, s. 681-684 Tidskriftsartikel (refereegranskat)abstract This paper demonstrates a fully integrated master-slave emitter-coupled logic (ECL)comparator and a frequency divider implemented in 4H-SiC bipolar technology. The comparator consists of two latch stages, two level shifters and an output buffer stage. The circuits have been tested up to 500 °C. The single ended output swing of the comparator is -7.73 V at 25 °C and-7.63 V at 500 °C with a -15 V supply voltage. The comparator consumes 585 mW at 25 °C. The frequency divider consisting of two latches shows a relatively constant output voltage swing over the wide temperature range. The output voltage swing is 7.62 V at 25 °C and 7.32 V at 500 °C.
14.	Hellström, Kristina, et al. (författare) Density variations during solidification of grey cast Iron 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; , s. 155-162 Tidskriftsartikel (refereegranskat)abstract As part of moving towards a sustainable production of diesel engines for heavy vehicle applications, the ability to predict casting defects has become ever so important. In order to model the solidification process for cast components correctly, it is of essence to know how the material will actually behave. To produce sound castings, often of complex geometry, the industry relies on various simulation software for the prediction and avoidance of defects. Thermophysical properties, such as density, play an important part in these simulations. Previous measurements of how the volume of liquid grey iron changes with temperature has been made with a conventional dilatometer. Measurements have also been made in the austenitic range, then on iron-carbon-silicon alloys with a carbon content lower than 1.5 wt%. Based on these measurements the density variations during solidification were calculated. The scope for this paper is to model the volume changes during solidification with the control volume finite difference method, using data from the density measurements.
15.	Hernando, Juan Carlos, et al. (författare) On the primary solidification of compacted graphite iron : Microstructure evolution during isothermal coarsening 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 90-97 Tidskriftsartikel (refereegranskat)abstract It is widely accepted that in most commercial hypoeutectic alloys, both static mechanicalproperties and feeding characteristics during solidification, are extremely linked to the coarseness ofthe primary phase. It is therefore of critical importance to provide tools to control and predict thecoarsening process of the dendritic phase present in hypoeutectic melts. The characterization of theprimary phase, a product of the primary solidification, has traditionally been neglected whencompared to the eutectic solidification characterization in cast iron investigations. This workpresents the morphological evolution of the primary austenite present in a hypoeutectic compactedgraphite cast iron (CGI) under isothermal conditions. To that purpose, a base spheroidal graphitecast iron (SGI) material with high Mg content is re-melted in a controlled atmosphere and reversedinto a CGI melt by controlling the Mg fading. An experimental isothermal profile is applied to thesolidification process of the experimental alloy to promote an isothermal coarsening process of theprimary austenite dendrite network during solid and liquid coexistence. Through interruptedsolidification experiments, the primary austenite is preserved and observed at room temperature. Byapplication of stereological relations, the primary phase and its isothermal coarsening process arecharacterized as a function of the coarsening time applied. The microstructural evolution observedin the primary austenite in CGI and the measured morphological parameters show a similar trend tothat observed for lamellar graphite cast iron (LGI) in previous investigations. The modulus of theprimary austenite, Mγ, and the nearest distance between the centre of gravity of neighbouringaustenite particles, Dγ, followed a linear relation with the cube root of coarsening time.
16.	Kargarrazi, Saleh, et al. (författare) Design and characterization of 500°c schmitt trigger in 4H-SiC 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783038354789 ; 821-823, s. 897-901 Tidskriftsartikel (refereegranskat)abstract Two versions of Schmitt trigger, an emitter-coupled and an operational amplifier (opamp)-based, are implemented in 4H-SiC bipolar technology and tested up to 500 °C. The former benefits the simplicity, smaller footprint, and fewer number of devices, whereas the latter provides better promise for high temperature applications, thanks to its more stable temperature characteristics. In addition, the measurements in the range 25 °C - 500 °C, shows that the opamp-based version provides negative and positive slew rates of 4.8 V/μs and 8.3 V/μs, ~8 and ~3 times higher than that of the emitter-coupled version, which are 1.7 V/μs and 1 V/μs.
17.	Karhu, Robin, 1987-, et al. (författare) Long Charge Carrier Lifetime in As-Grown 4H-SiC Epilayer 2016 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 858, s. 125-128 Tidskriftsartikel (refereegranskat)abstract Over 150 μm thick epilayers of 4H-SiC with long carrier lifetime have been grown with a chlorinated growth process. The carrier lifetime have been determined by time resolved photoluminescence (TRPL), the lifetime varies a lot between different areas of the sample. This study investigates the origins of lifetime variations in different regions using deep level transient spectroscopy (DLTS), low temperature photoluminescence (LTPL) and a combination of KOH etching and optical microscopy. From optical microscope images it is shown that the area with the shortest carrier lifetime corresponds to an area with high density of structural defects.
18.	Karhu, Robin, et al. (författare) The Role of Chlorine during High Growth Rate Epitaxy 2015 Ingår i: Materials Science Forum. - Pfaffikon, Switzerland : Scientific.Net. - 0255-5476 .- 1662-9752. ; 821-823, s. 141-144 Tidskriftsartikel (refereegranskat)abstract The influence of chlorine has been investigated for high growth rates of 4H-SiC epilayers on 4o off-cut substrates. Samples were grown at a growth rate of approximately 50 and 100 μm/h and various Cl/Si ratios. The growth rate, net doping concentration and charge carrier lifetime have been studied as a function of Cl/Si ratio. This study shows some indications that a high Cl concentration in the growth cell leads to less availability of Si during the growth process.
19.	Kasvayee, Keivan Amiri, 1986-, et al. (författare) Effect of Boron and Cross-Section Thickness on Microstructure and Mechanical Properties of Ductile Iron 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 249-256 Tidskriftsartikel (refereegranskat)abstract 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.
20.	Khosa, Rabia Y., et al. (författare) Electrical characterization of MOCVD grown single crystalline ALN thin films on 4H-SiC 2019 Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 1662-9752 .- 0255-5476. ; 963 MSF, s. 460-464, s. 460-464 Konferensbidrag (refereegranskat)abstract We report on a very low density of interface traps at the AlN/4H-SiC interface estimated from capacitance-voltage (CV) analysis of metal-insulator-semiconductor (MIS) capacitors. Single crystalline aluminum nitride (AlN) films are grown by metal organic chemical vapor deposition (MOCVD). Current-voltage (IV) analysis shows that the breakdown electric field across the AlN dielectric is 3 MV/cm. By depositing an additional SiO2 layer on top of the AlN layer it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC interface.
21.	Khosa, Rabia Y., et al. (författare) Low density of near-interface traps at the Al2O3/4H-SiC interface with Al2O3 made by low temperature oxidation of Al 2017 Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 1662-9752 .- 0255-5476. - 9783035710434 ; 897 MSF, s. 135-138, s. 135-138 Konferensbidrag (refereegranskat)abstract We report on a very low density (
22.	Klement, Uta, 1962, et al. (författare) EBSD Analysis and Assessment of Porosity in Thermal Barrier Coatings Produced by Axial Suspension Plasma Spraying (ASPS) 2017 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 1662-9752 .- 0255-5476. - 9783035711295 ; 879, s. 972-977, s. 972-977 Konferensbidrag (refereegranskat)abstract Axial suspension plasma spraying (ASPS) is a relatively new, innovative sprayingtechnique which has produced thermal barrier coatings (TBCs) with attractive properties such ashigh durability and low thermal conductivity. Using a suspension, it is possible to spray with finerpowder particles resulting in coatings that have a columnar microstructure and contain a wide rangeof pore sizes, both nm- and μm-sized pores. To optimize the thermal properties and to maintainthem during service of the components, it will be important to design TBCs with optimal porosity.Hence, an important part in the assessment of ASPS coatings is therefore the characterization of themicrostructure and how it is build up, and the determination of porosity. Both aspects are addressedby performing measurement on splats and ASPS-coating using electron backscatter diffraction(EBSD) technique and by measuring porosity by Mercury Intrusion Porosimetry (MIP).
23.	Koptyug, Andrey, 1956-, et al. (författare) New Metallurgy of Additive Manufacturing in Metal : Experiences from the Material and Process Development with Electron Beam Melting Technology (EBM) 2016 Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 879, s. 996-1001 Tidskriftsartikel (refereegranskat)abstract Additive manufacturing (AM) is becoming one of the most discussed modern technologies. Significant achievements of the AM in metals today are mainly connected to the unprecedented freedom of component shapes this technology allows. But full potential of these methods lies in the development of new materials designed to be used specifically with AM. Proper understanding of the AM process will open up new possibilities, where material and component properties can be specifically tailored by controlling the parameters throughout the whole manufacturing process. Present paper discusses the issues related to the beam melting technologies AM and electron beam welding (EBW). We are speaking of new direction in material science that can be termed “non-stationary metallurgy”, using the examples from material and process development for EBW, electron beam melting (EBM®) and other additive manufacturing methods.
24.	Krajňáková, P.G., et al. (författare) Effect of double electron beam remelting on microstructure of HVOF and CGDS bond coat 2017 Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. - 9783035710182 ; 891, s. 574-578 Konferensbidrag (refereegranskat)abstract This work focuses to investigate the influence of the parameters used in electron beam (EB) remelting including the effect of double remelting of CoNiCrAlY coatings fabricated on Nickel based super alloy substrates by using the high velocity oxygen-fuel (HVOF) and cold gas dynamic spraying (CGDS) methods. The microstructure of as sprayed and remelted coatings were investigated by scanning electron microscopy and the phase analysis by X-ray diffraction (XRD). The results obtained show that there are advantages at using the pulsed EB surface modification technique. Double EB treatment provides a smooth surface and low porosity level and at last but not least this study demonstrate that low-temperature processing of CoNiCrAlY bond coat represents an interesting and promising alternative for their manufacturing.
25.	Kurose, T., et al. (författare) Low-parasitic-capacitance self-aligned 4H-SiC nMOSFETs for harsh environment electronics 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035711455 ; 924, s. 971-974 Tidskriftsartikel (refereegranskat)abstract Low-parasitic-capacitance 4H-SiC nMOSFETs using a novel self-aligned process were suggested and demonstrated. In these nMOSFETs, device characteristics including parasitic capacitances (gate-source, gate-drain, drain-source capacitance) were investigated and low parasitic capacitance was achieved by the self-aligned structure
26.	Lanni, Luigia, et al. (författare) ECL-based SiC logic circuits for extreme temperatures 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 821-823, s. 910-913 Tidskriftsartikel (refereegranskat)
27.	Li, Fan, et al. (författare) Electrical Characterisation of Thick 3C-SiC Layers Grown on Off-Axis 4H-SiC Substrates 2019 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 963, s. 353-356 Tidskriftsartikel (refereegranskat)abstract 300 μm thick 3C-SiC epilayer was grown on off-axis 4H-SiC(0001) substrate with a high growth rate of 1 mm/hour. Dry oxidation, wet oxidation and N2O anneal were applied to fabricate lateral MOS capacitors on these 3C-SiC layers. MOS interface obtained by N2O anneal has the lowest interface trap density of 3~4x1011 eV-1cm-2. Although all MOS capacitors still have positive net charges at the MOS interface, the wet oxidised sample has the lowest effective charge density of ~9.17x1011 cm-2.
28.	Lim, Jang-Kwon, et al. (författare) Temperature-dependent characteristics of 4H-SiC buried grid JBS diodes 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 9783038354789 ; 821/823, s. 600-603 Konferensbidrag (refereegranskat)abstract 4H-SiC Schottky Barrier Diodes (SBD) have been developed using p-type buried grids (BGs) formed by Al implantation. In order to reduce on-state resistance and improve forward conduction, the doping concentration of the channel region between the buried grids was increased. The fabricated diodes were encapsulated with TO-254 packages and electrically evaluated. Experimental forward and reverse characteristics were measured in the temperature range from 25 °C to 250 °C. On a bare die level, the forward voltage drop was reduced from 5.36 V to 3.90 V at 20 A as the channel doping concentration was increased in order to reduce the channel resistance. After encapsulation in a TO-254 package, the forward voltage drop was decreased by approximately 10% due to a lower contact resistance. The on-state resistance of an identical device measured on the bare die and in the TO-254 package increased with increasing temperature due to the decreased electron mobility in the drift region resulting in higher resistance. The incremental contact resistances of the bare dies were larger than in the packaged devices. One key issue associated with conventional Junction Barrier Schottky (JBS) diodes is a high leakage current at high temperature operation over 200 °C. The developed Buried Grid JBS (BG JBS) diode has significantly reduced leakage current due to a better field shielding at the Schottky contact. The leakage current of the packaged BG JBS diodes is compared to conventional SBD and commercial JBS diodes.
29.	Linnarsson, Margareta K., et al. (författare) Channeling implantations of p-type dopants into 4H-SiC at different tempertures 2019 Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. ; 963, s. 382-385 Tidskriftsartikel (refereegranskat)abstract Channeling of B and Al ions in 4H-SiC(0001), has been investigated by secondary ion mass spectrometry (SIMS). Ion implantations have been performed between room temperature (RT) and 600 °C at various fluences. Before implantation, the major crystal axes were determined and the sample was aligned using the blocking pattern of backscattered protons. As expected, the depth distribution of the implanted ions along a crystal direction penetrates much deeper compared to nonchanneling directions. At elevated temperatures, the channeling depth for 100 keV Al-ions is decreased due to lattice vibrations. For 50 keV B-ions, the temperature effect is minor, indicating a smaller interaction between target atoms and B. Simulations has been performed using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation, to predict experimental data and get a deeper insight in the channeling process.
30.	Liu, Fang, 1975, et al. (författare) Microstructure of Z-Phase Strengthened Martensitic Steels: Meeting the 650°C Challenge 2017 Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 879, s. 1147-1152 Konferensbidrag (refereegranskat)abstract We studied three series of Z-phase strengthened steels using scanning electron microscopy, transmission electron microscopy, and atom probe tomography to reveal the detailed microstructure of these steels. In particular, the phase transformation from M(C,N) to Z-phase (CrMN) was studied. Carbon content in the steels is the governing factor in this transformation. The impact toughness of some test alloys was rather low. This is attributed to the formation of a continuous W-rich film along prior austenite grain boundaries. Cu and C addition to the test alloys changed Laves phase morphology to discrete precipitates and improved toughness dramatically. BN particles were found in some steels. Formation of BN is directly linked to the B concentration in the steels.
31.	Ma, Quanbao, et al. (författare) Characterization of B-Implanted 3C-SiC for Intermediate Band Solar Cells 2017 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 897, s. 299-302 Tidskriftsartikel (refereegranskat)abstract Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×1017 atoms/cm2 in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×1021 cm-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density.
32.	Molnar, David, et al. (författare) Deformation properties of austenitic stainless steels with different stacking fault energies 2018 Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. ; 941, s. 190-197, s. 190-197 Tidskriftsartikel (refereegranskat)abstract In FCC metals a single parameter – stacking fault energy (SFE) – can help to predict the expectable way of deformation such as martensitic deformation, deformation twinning or pure dislocation glide. At low SFE one can expect the perfect dislocations to dissociate into partial dislocations, but at high SFE this separation is more restricted. The role of the magnitude of the stacking fault energy on the deformation microstructures and tensile behaviour of different austenitic steels have been investigated using uniaxial tensile testing and electron backscatter diffraction (EBSD). The SFE was determined by using quantum mechanical first-principles approach. By using plasticity models we make an attempt to explain and interpret the different strain hardening behaviour of stainless steels with different stacking fault energies.
33.	Nygren, Håkan, et al. (författare) MgO implanted in rat tibia bone marrow is osteoinductive through the formation of a matrix, containing hydroxyapatite 2017 Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 879, s. 1404-1407 Konferensbidrag (refereegranskat)abstract Healing of rat tibia after intramedullary implantation of MgO was analysed by Environmental Scanning Electron Microscopy (ESEM) and Energy-Dispersive X-ray spectroscopy (EDX). The results indicated the formation of hydroxyl-apatite (HA) in the entire intramedullary space after 1 week of healing. Then, corroded Mg, MgO and MgCO3 were incubated with DMEM in vitro for 24 h and the surface of the material was analysed by EDX and Time-of-Flight Secondary Ion Mass (ToF-SIMS). The chemical analysis of the Mg corrosion products indicate that HA is formed at the material surface and that MgCO3 was an efficient catalyzer of HA formation. © 2017 Trans Tech Publications, Switzerland.
34.	Puglisi, Donatella, et al. (författare) Exploring the gas sensing performance of catalytic metal/ metal oxide 4H-SiC field effect transistors 2016 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 858, s. 997-1000 Tidskriftsartikel (refereegranskat)abstract Gas sensitive metal/metal-oxide field effect transistors based on silicon carbide were used to study the sensor response to benzene (C6H6) at the low parts per billion (ppb) concentration range. A combination of iridium and tungsten trioxide was used to develop the sensing layer. Highsensitivity to 10 ppb C6H6 was demonstrated during several repeated measurements at a constant temperature from 180 to 300 °C. The sensor performance was studied also as a function of the electrical operating point of the device, i.e., linear, onset of saturation, and saturation mode. Measurements performed in saturation mode gave a sensor response up to 52 % higher than those performed in linear mode.
35.	Rankl, Dominik, et al. (författare) Quantitative Study on the Role of Supersaturation during Sublimation Growth on the Yield of 50 mm diameter 3C-SiC 2015 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 821, s. 77-80 Tidskriftsartikel (refereegranskat)abstract We have investigated the growth of 3C-SiC using sublimation growth in the temperature range from 1800°C to 1950°C. The supersaturation was determined using numerical modeling of the temperature field and gas phase composition by applying quasi-equilibrium thermodynamic conditions. Analysis of the 3C-SiC yield was carried out by optical microscopy, optical absorption, Raman spectroscopy and x-ray analysis. Quantitative data on supersaturation are compared with most stable 3C-SiC nucleation and growth condition. Finally the application to large area growth in a physical vapor transport growth reactor is briefly addressed.
36.	Safara Nosar, Nima, et al. (författare) Characterization of hot deformation behavior in a 13% chromium steel 2018 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 941, s. 458-467 Tidskriftsartikel (refereegranskat)abstract The behavior of a 13% chromium steel subjected to hot deformation has been studied by performing hot compression tests in the temperature range of 850 to 1200 ⁰C and strain rates from 0.01 to 10 s-1. The uniaxial isothermal compression tests were performed on a Gleeble thermo-mechanical simulator. The best function that fits the peak stress for the material and its relation to the Zener-Hollomon parameter (Z) is illustrated. The average activation energy of this alloy for the entire test domain was reviled to be about 557 [kJ mol-1] from the calculations and the dynamic recrystallization (DRX) kinetic were studied to find the fraction DRX in the course of deformation.
37.	Saketi, Sara, et al. (författare) Wear behaviour of two different cemented carbide grades in turning 316 L stainless steel 2018 Ingår i: Materials Science Forum. - : TRANS TECH PUBLICATIONS LTD. - 0255-5476 .- 1662-9752. ; 941, s. 2367-2372, s. 2367-2372 Tidskriftsartikel (refereegranskat)abstract Cemented carbides are the most common cutting tools for machining various grades of steels. In this study, wear behavior of two different cemented carbide grades with roughly the same fraction of binder phase and carbide phase but different grain size, in turning austenitic stainless steel is investigated. Wear tests were carried out against 316L stainless steel at 180 and 250 m/mincutting speeds. The worn surface of cutting tool is characterized using high resolution scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and 3D optical profiler.The wear of cemented carbide in turning stainless steel is controlled by both chemical and mechanical wear. Plastic deformation, grain fracture and chemical wear is observed on flank and rake face of the cutting insert. In the case of fine-grained, the WC grains has higher surface contact with the adhered material which promotes higher chemical reaction and degradation of WC grains, so chemical wear resistance of the composites is larger when WC grains are larger. The hardness of cemented carbide increase linearly by decreasing grain size, therefore mechanical wear resistance of the composites is larger when WC grains are smaller.
38.	Salemi, Arash, et al. (författare) Investigation of the breakdown voltage in high voltage 4H-SiC BJT with respect to oxide and interface charges 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9783038354789 ; 821-823, s. 834-837 Tidskriftsartikel (refereegranskat)abstract Ion implantation in silicon carbide (SiC) induces defects during the process. Implantation free processing can eliminate these problems. The junction termination extension (JTE) can also be formed without ion implantation in SiC bipolar junction transistor (BJT) using a well-controlled etching into the epitaxial base layer. The fixed charges at the SiC/SiO2 interface modify the effective dose of the JTEs, leakage current, and breakdown voltage. In this paper the influence of fixed charges (positive and negative) and also interface trap density at the SiC/SiO2 interface on the breakdown voltage in 4.5 kV 4H-SiC non-ion implanted BJT have been simulated. SiO2 as a surface passivation layer including interface traps and fixed charges has been considered in the analysis. Simulation result shows that the fixed charges influence the breakdown voltage significantly more than the interface traps. It also shows that the positive fixed charges reduce the breakdown voltage more than the negative fixed charges. The combination of interface traps and fixed charges must be considered when optimizing the breakdown voltage.
39.	Salomonsson, Kent, et al. (författare) Three-dimensional microstructural characterization of cast iron alloys for numerical analyses 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 427-435 Tidskriftsartikel (refereegranskat)abstract In this paper, we aim at characterizing three different cast iron alloys and their microstructural features, namely lamellar, compacted and nodular graphite iron. The characterization of microscopic features is essential for the development of methods to optimize the behavior of cast iron alloys; e.g. maximize thermal dissipation and/or maximize ductility while maintaining strength. The variation of these properties is commonly analyzed by metallography on two-dimensional representations of the alloy. However, more precise estimates of the morphologies and material characteristics are obtained by three-dimensional reconstruction of microstructures. The use of X-ray microtomography provides an excellent tool to generate high resolution threedimensional microstructure images. The characteristics of the graphite constituent in the microstructure, including the size, shape and connectivity, were analyzed for the different cast iron alloys. It was observed that the lamellar and compacted graphite iron alloys have relatively large connected graphite morphologies, as opposed to ductile iron where the graphite is present as nodules. The results of the characterization for the different alloys were ultimately used to generate finite element models.
40.	Sjölander, Emma, et al. (författare) Influence of Quench Rate on the Artificial Ageing Response of an Al-8Si-0.4Mg Cast Alloy 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 828-829, s. 219-225 Tidskriftsartikel (refereegranskat)abstract The aim of the study is to present the influence of quench rate on the artificial ageing response of Al-8%Si-0.4%Mg cast alloy in terms of Brinell hardness and yield strength. The investigated material was produced by a gradient solidification technique and exhibited a microstructure that corresponds to the one of gravity die castings, with a dendrite arm spacing of approximately 25 μm. The study comprises two solution treatment temperatures, five quench rates and artificial ageingtimes exceeding 100 hours at 170 and 220 ⁰C. The microstructure and concentration profiles of Mgand Si were evaluated using energy and wavelength dispersive spectroscopy. Microstructural examination reveals an increment of solutes in the Al-matrix when higher solution treatment temperatures accompanied with high quench rates are applied and shows how both Si and Mgatoms have diffused towards the eutectic during quenching. Consequently, i.e. by increasing the levels of solutes and vacancies, the highest strength levels were realized. The study confirmed that quench rates above 2 ⁰C /s do not offer substantial strength improvement while quenching at lower rates resulted in a lower peak hardness and longer times to peak.
41.	Skoglund, Peter, et al. (författare) Thermo-mechanical fatigue of grey cast iron for cylinder heads - Effect of niobium, molybdenum and solidification time 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 377-384 Tidskriftsartikel (refereegranskat)abstract Grey iron alloyed with molybdenum and niobium in seven different compositions has been casted using three, in industrial components viable, solidification times which resulted in 21 different samples. The samples have been investigated with respect to microstructure, static properties and thermo-mechanical fatigue performance. It was found that the solidification time is very important for both the static and thermo-mechanical performance. If the solidification time is long the properties are controlled entirely by the large graphite flakes and there is no influence of the alloying elements. On the other hand if the solidification time can be kept short the need for alloying elements may be removed. For the shorter solidification times an influence from the matrix and thus the alloying elements can be seen. It was found that molybdenum enhances TMF-life while no such effect was found for niobium. Niobium, on the other hand, has a larger effect on static strength than molybdenum and also on the cyclic stress in the thermo-mechanical fatigue experiments.
42.	Smedfors, Katarina, et al. (författare) Sputtered Ohmic Cobalt Silicide Contacts to 4H-SiC 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 821-823, s. 440-443 Tidskriftsartikel (refereegranskat)abstract Ohmic CoSi2 contacts to n-type 4H-SiC showing low contact resistance have been made by sputter depositing sequential layers of Si and Co on 4H-SiC substrates followed by a two-step rapid thermal anneal at 600 °C and 950 °C. The contacts formed have been characterized at temperatures ranging from-40 °C to 500 °C with a specific contact resistance of 3.80∙10-5 Ωcm2 at 25 °C and a minimum of 6.0∙10-6 Ωcm2 at 500 °C.
43.	Suvanam, Sethu Saveda, et al. (författare) Tailoring the interface between dielectric and 4H-SiC by ion implantation 2015 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 821-823, s. 488-491 Tidskriftsartikel (refereegranskat)abstract In this paper, the effect of carbon (C), silicon (Si) and nitrogen (N) implantation on the interface properties of 4H-SiC/SiO2 and the implications for 4H-SiC bipolar junction transistors (BJT) passivation are discussed. 4H-SiC epi-layer have been implanted with12C,14N and28Si ion at three different doses with energies of 3, 3.5 and 6 keV, respectively, resulting in a projected range of 8 nm for the three ions. Then metal oxide semiconductor (MOS) structures with SiO2 as dielectric have been fabricated. Capacitance voltage measurements show an increase in the negative fixed charges for all the implanted samples as a function of implantation induced damage. Similarly, in the case of C and Si, the surface roughness increases as a function of dose and the mass of the ions. No reduction of Dits due to the implantations is seen for any of the ions. Furthermore, TCAD device simulations of npn bipolar junction transistors (BJT), using the interface and fixed charges extracted from CV measurements, show a way to further optimize current gain and breakdown properties for the BJT.
44.	Svensson, Ingvar L., et al. (författare) Mathematical characterization of the tensile deformation curve of cast iron materials 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 444-450 Tidskriftsartikel (refereegranskat)abstract The manufacturing process gives cast iron castings properties which are dependent on component design, metallurgy and casting method. Factors such as local wall thickness influences the coarseness and type of microstructure and the castings will have local properties depending on the local metallurgical and thermal history. The stress/strain behaviour of cast materials is typically determined by performing a tensile test in a tensile test machine. The deformation behaviour will normally be determined by two mechanisms, namely, elastic and plastic phenomena. The plastic behaviour is based on dislocation movements in the lattice. Commonly, the deformation history of cast iron involves elastic, plastic and crack phases. The cast iron material has a complex microstructure and first order equations cannot be used to predict the deformation during loading. Until methods have been developed, the characterization of complex microstructure materials such as cast iron has to be determined by use of empirical methods. The empirical methods have to couple the internal microstructure and composition of the material with deformation phenomena during loading. The paper will show a method to characterize tensile test curves of cast iron materials which can be used to couple deformation phenomena with for example microstructure. The equations are aimed to make the tensile test curve ready for curve fitting and optimization in two steps. Each stress/strain curve is like a finger print of the material and requires well performed tests and some advices are given. The paper also wants to encourage researchers and people working with tensile testing to get out more of their effort to measure strength of cast iron materials and connect the result to the microstructure of the specimens.
45.	Svidró, Péter, 1980-, et al. (författare) Extended method of volume change measurements during solidification of lamellar graphite iron 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 163-170 Tidskriftsartikel (refereegranskat)abstract Lamellar graphite iron (LGI) is an important technical alloy used to produce cast components for the automotive and the marine industry. The performance of the component is defined by the solidification sequence. Therefore, a lot of research work has been done in the field of solidification. The present work introduces a new measurement approach that combines advanced dilatation measurements with thermal analysis to investigate the solidification of LGI. The method involves a thermally balanced spherical sample. The temperature values are measured in the geometrical center and on the surface of the sample. The released heat of solidification is calculated by using the Fourier Thermal Analysis (FTA) method. The displacement values are measured on the surface of the sample. The volume change is calculated from the displacement data. The dilatation results clearly shows the advantage of the multidirectional measurement.
46.	Tamil Alagan, Nageswaran, 1990-, et al. (författare) Next Generation Insert for Forced Coolant Application in Machining of Inconel 718 2016 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 836-837, s. 340-347 Tidskriftsartikel (refereegranskat)abstract Machining technology has undergone an extensive evolution throughout the last decades in its capability to machine hard-to-cut material. This paper will discuss about the next generation insert with cooling feature coupled with forced coolant in machining Inconel 718. The geometry of the insert was changed in a way which has enlarged the surface area approximately 12% compared to regular insert named as nusselt insert. The idea applied in “nusselt insert” was the relation of increase in surface area to heat dissipation. Forced coolant application has become a way to improve existing metal cutting concepts and improve their current material removal rates without any need for a reengineered machining process. Experiments conducted on the inserts is that the first experiment of its kind in machining technology together with forced coolant and tested in four different inserts. The primary focus of the work was the investigation of the relation between the heat dissipation with an increase in surface area/mass ratio in the cutting interface based on its influence on tool wear. The experimental results showed the nusselt insert have better ability for heat dissipation which has led to significant reduce in tool wear and successfully facing Inconel 718 at vc 105 m/min, f 0.3 mm/rev and ap 1 mm where the regular insert had a catastrophic failure at vc 90 m/min, f 0.1 mm/rev and ap 1 mm. Nusselt insert has shown to increase MRR significantly compared to regular insert.
47.	Thomser, Corinna, et al. (författare) Influence of local microstructure on stresses, durability and fracture mechanics of cast iron components 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 264-271 Tidskriftsartikel (refereegranskat)abstract Cast iron components show a large variety of different microstructures in dependence on chemical composition, inoculation and cooling conditions. In conventional static and dynamic calculations as well as in fracture mechanics assessment of cast iron components, the influence of local microstructure on the overall behavior of the component is not considered. Usually one material dataset is applied for the whole material. The paper describes recent developments in the field of the prediction of local microstructure and its correlation to local stress-strain, fatigue durability as well as fracture toughness. The benefit of combining casting process simulation with lifetime predictions and fracture mechanics assessment is shown for selected examples. By integrating casting process simulation, microstructure modelling, local material characterization and load analysis, a simulation based approach for predicting the behavior and performance of cast iron components already during the design stage is enabled. Thus, the local assessment helps designers to assess risks and strive for light weight designs before the casting is made.
48.	Tian, Ye, et al. (författare) A 500 °C monolithic SiC BJT latched comparator 2016 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710427 ; 858, s. 921-924 Tidskriftsartikel (refereegranskat)abstract This paper presents a monolithic 4H-SiC BJT latched emitter-coupled logic (ECL) comparator for high temperature analog-to-digital conversion. The comparator consists of a low-gain pre-amplifier, a track and latch stage and an output buffer. For low-speed input signals, the comparator input offset voltage is 3.9 mV at 27 ºC and monotonically increases up to 9.1 mV at 500ºC. The single-ended output swing is 5.5 V at 27 ºC and 3.9 V at 500 ºC. The minimum comparison time is around 1 μs from 27 ºC to 500 ºC. The whole comparator dissipates 464 mW in average over the considered temperature range with a 15 V power supply. It consumes 2.25 × 0.84 mm2 chip area (with the bond pads included).
49.	Toth-Pal, Zsolt, et al. (författare) Investigation of pressure dependent thermal contact resistance between silver metallized SiC chip and DBC substrate 2015 Ingår i: European Conference on Silicon Carbide and Related Materials, ECSCRM 2014. - : Trans Tech Publications Inc.. - 9783038354789 ; 821-823, s. 452-455 Konferensbidrag (refereegranskat)abstract Thermal contact resistances between a silver metallized SiC chip and a direct bonded copper (DBC) substrate have been measured in a heat transfer experiment. A novel experimental method to separate thermal contact resistances in multilayer heat transfer path has been demonstrated. The experimental results have been compared both with analytical calculations and with 3D computational fluid dynamics (CFD) simulation results. A simplified CFD model of the experimental setup has been validated. The results show significant pressure dependence of the thermal contact resistance but also a pressure independent part.
50.	Xiang, Shengmei, 1991-, et al. (författare) High-Temperature Corrosion-Fatigue Behavior of Ductile Cast Irons for Exhaust Manifolds Applications 2018 Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 925, s. 369-376 Tidskriftsartikel (refereegranskat)abstract In the present study, low-cycle fatigue (LCF) tests and oxidation tests in controlled atmospheres are carried out at 800ºC on two ductile cast irons SiMo51 and SiMo1000. The LCF tests are conducted in argon and synthetic exhaust gas, whereas oxidation tests are carried out in the latter atmosphere. S-N curves and weight-gain curves are presented. The crack growth mechanisms and oxidation mechanisms are investigated, as well as the synergistic effects. A surprising finding of increased fatigue resistance in the oxidizing atmosphere is partly explained.

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