The Experts below are selected from a list of 14865 Experts worldwide ranked by ideXlab platform
Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.
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Bone-like crack resistance in hierarchical metastable nanolaminate Steels
Science, 2017Co-Authors: Motomichi Koyama, Dirk Ponge, Kaneaki Tsuzaki, Dierk Raabe, Zhao Zhang, Meimei Wang, Hiroshi Noguchi, Cemal Cem TasanAbstract:Fatigue failures create enormous risks for all engineered structures, as well as for human lives, motivating large safety factors in design and, thus, inefficient use of resources. Inspired by the excellent fracture toughness of bone, we explored the fatigue resistance in metastability-assisted multiphase Steels. We show here that when Steel Microstructures are hierarchical and laminated, similar to the substructure of bone, superior crack resistance can be realized. Our results reveal that tuning the interface structure, distribution, and phase stability to simultaneously activate multiple micromechanisms that resist crack propagation is key for the observed leap in mechanical response. The exceptional properties enabled by this strategy provide guidance for all fatigue-resistant alloy design efforts.
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vessel microstructure design a new approach for site specific core shell micromechanical tailoring of trip assisted ultra high strength Steels
Acta Materialia, 2016Co-Authors: Michael Martinus Belde, Hauke Springer, Dierk RaabeAbstract:Abstract The mechanical performance of multi-phase Steel Microstructures critically depends on the constituents’ chemical and morphological constitutions, which in combination determine the composite hardness, the onset of plasticity, internal load and strain-partitioning, as well as the stability and transformation kinetics of retained austenite in case of TRIP Steels. The novel approach of utilising temporary vessel phases, hence termed vessel microstructure design, enables the tuning of constituent phase properties by linking their formation to a controllable landscape of chemical gradients. This approach hinges on the introduction of alloy carbides as a temporary container, or ‘vessel’ phase, deliberately producing localised enrichment of alloying elements in a structure predetermined by preliminary heat treatments, referred to as conditioning and accumulation stages. These vessel carbides, which act as reservoirs for specific alloying elements, are then partially dissolved through flash heating, leading to a self-organising landscape of alloying elements in the vicinity of the dissolving particles. The resulting three- or multiple phase Microstructures then consist of confined laminates incorporating retained carbides, enveloped by retained austenite shells, embedded within a martensitic matrix. Such complex yet entirely self-organized Microstructures offer unique opportunities for strain and load partitioning which we refer to as core-shell micromechanics. Different variants of these core-shell composite structures are produced and examined together with reference Microstructures by tensile testing, hardness mappings, impact toughness, X-ray measurements, as well as by electron microscopy. It is found that these novel Microstructures, when tempered, exhibit ultra-high strength and delayed necking, enabled by a combination of gradual strain-hardening and transformation-induced plasticity that is tuneable via control of the initial carbide structure.
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advances in the optimization of thin strip cast austenitic 304 stainless Steel Microstructures
Steel Research International, 2008Co-Authors: Dierk Raabe, Rolf Degenhardt, Roland Sellger, Wilfried Dr Klos, M Sachtleber, Lutz ErnenputschAbstract:This study is about the latest advances in the optimization of the microstructure and properties of thin strip cast austenitic stainless Steel (AISI 304, 1.4301). Concerning the processing steps the relevance of different thin strip casting parameters, in-line forming operations, and heat treatments for optimizing microstructure and properties have been studied. The Microstructures obtained from the different processing strategies were analysed with respect to phase and grain structures including the grain boundary character distributions via EBSD microtexture measurements, the evolution of deformation-induced martensite, the relationship between delta ferrite and martensite formation in austenite, and the texture evolution during in-line deformation. It is observed that different process parameters lead to markedly different Microstructures and profound differences in strip homogeneity. It is demonstrated that the properties of strip cast and inline hot rolled austenitic stainless Steels are competitive to those obtained by conventional continuous casting and hot rolling. This means that the thin strip casting technique is not only competitive to conventional routes with respect to the properties of the material but also represents the most environmentally friendly, flexible, energy-saving, and modern industrial technique to produce stainless Steel strips.
Elena V Pereloma - One of the best experts on this subject based on the ideXlab platform.
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effect of deformation on microstructure and mechanical properties of dual phase Steel produced via strip casting simulation
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Zhiping Xiong, Andrii Kostryzhev, Nicole Stanford, Elena V PerelomaAbstract:Abstract The strip casting is a recently appeared technology with a potential to significantly reduce energy consumption in Steel production, compared to hot rolling and cold rolling. However, the quantitative dependences of the Steel microstructure and mechanical properties on strip casting parameters are unknown and require investigation. In the present work we studied the effects of strain and interrupted cooling temperature on microstructure and mechanical properties in conventional dual phase Steel (0.08C–0.81Si–1.47Mn–0.03Al wt%). The strip casting process was simulated using a Gleeble 3500 thermo-mechanical simulator. The Steel Microstructures were studied using optical, scanning and transmission electron microscopy. Mechanical properties were measured using microhardness and tensile testing. Microstructures consisting of 40–80% polygonal ferrite with remaining martensite, bainite and very small amount of Widmanstatten ferrite were produced. Deformation to 0.17–0.46 strain at 1050 °C refined the prior austenite grain size via static recrystallisation, which led to the acceleration of ferrite formation and the ferrite grain refinement. The yield stress and ultimate tensile strength increased with a decrease in ferrite fraction, while the total elongation decreased. The improvement of mechanical properties via deformation was ascribed to dislocation strengthening and grain boundary strengthening.
R Maeda - One of the best experts on this subject based on the ideXlab platform.
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injection molding debinding and sintering of 316l stainless Steel Microstructures
Applied Physics A, 2005Co-Authors: N H Loh, B.y. Tay, S B Tor, Yoichi Murakoshi, R MaedaAbstract:The micro powder injection molding (μPIM) process was used to fabricate metallic Microstructures in this paper. The production of 316L stainless Steel Microstructures arrays with the dimensions of ∅ 100 μm×height200 μmand∅ 60 μm × height 191 μm is presented. Injection molding was conducted on a conventional injection molding machine and silicon mold inserts with vertical sidewall made by deep reactive ion etching (DRIE) were used. Molded parts with Microstructures were well obtained after selecting suitable processing parameters based on the feedstock characteristics. Then the molded parts were debound catalytically and sintered. Sintering at different temperature was conducted under vacuum. The effects of sintering temperatures were evaluated based on the polished and etched micrographs of the sintered Microstructures. Finally Young’s Modulus of sintered microstructure was evaluated using nano-indenter.
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replication of metal Microstructures by micro powder injection molding
Materials & Design, 2004Co-Authors: N H Loh, Yutaka Murakoshi, Shu Beng Tor, R MaedaAbstract:Abstract In this paper, a study on the production of 316L stainless Steel Microstructures by μPIM (powder injection molding) is presented. Two types of mold inserts were used and the molding was conducted on a conventional injection molding machine. Based on the characteristics of the mold inserts and the feedstock, suitable processing parameters were selected. Some requirements for the production of the Microstructures are discussed. For example, a relatively high mold temperature, high injection pressure and holding pressure were required. The study showed that 316L stainless Steel Microstructures of φ100 × 200 μm can be injection molded, but there were incomplete filling and demolding problem in the case of smaller Microstructures of φ60 × 191 μm. The molded parts were successfully debound and sintered.
Trevor C. Lindley - One of the best experts on this subject based on the ideXlab platform.
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Electron backscattering diffraction study of acicular ferrite, bainite, and martensite Steel Microstructures
Materials Science and Technology, 2000Co-Authors: H.m. Flower, Trevor C. LindleyAbstract:AbstractThis study deals with acicular ferrite, bainite, and martensite Microstructures observed in three low alloy Steels. Electron backscattering diffraction (EBSD) was used to assess crystallographic features of these Microstructures. In each area studied by EBSD mapping, ‘crystallographic packets’ defined as clusters of points sharing the same crystallographic orientation were compared with ‘morphological packets’ observed in the corresponding light micrograph. Microtexture studies suggested that acicular ferrite and upper bainite grow with Nishiyama– Wassermann relationships with the parent austenite phase, whereas lower bainite and martensite consist of highly intricate packets having Kurdjumov–Sachs relationships with the parent phase. In all cases three highly misoriented texture components were found within each former austenite grain. Electron backscattering diffraction also gave information about the cleavage and intergranular reverse temper embrittlement fracture mechanisms of these Steels. In...
I Karaman - One of the best experts on this subject based on the ideXlab platform.
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the role of heat treatment on the cyclic stress strain response of ultrafine grained interstitial free Steel
International Journal of Fatigue, 2008Co-Authors: Thomas Niendorf, D Canadinc, H J Maier, I KaramanAbstract:Abstract Thermal stability of ultrafine-grained (UFG) interstitial free (IF) Steel was investigated in order to establish heat treatments for obtaining recovered and bimodal UFG IF Steel Microstructures, as part of an effort to further improve the fatigue response of this material. The initial UFG microstructure was obtained using equal channel angular extrusion at room temperature. Microstructural investigations, such as electron backscattering diffraction and transmission electron microscopy, were carried out in order to observe the microstructural evolution due to heat treatment and fatigue. Cyclic tests at room temperature revealed the role of heat treatment and resulting Microstructures on the cyclic stress–strain response of the IF Steel. We demonstrate that the fatigue performance could be improved significantly with low temperature annealing. The bimodal microstructure, however, is not beneficial to improving fatigue properties of the UFG IF Steel. Finally, the stability of the UFG microstructure, and the absence of localized damage during fatigue is associated with the presence of impurities in the IF Steel.