The Experts below are selected from a list of 96 Experts worldwide ranked by ideXlab platform
G C Kaschner - One of the best experts on this subject based on the ideXlab platform.
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mechanical response of zirconium i derivation of a polycrystal constitutive law and finite element analysis
Acta Materialia, 2001Co-Authors: C N Tome, Ricardo A Lebensohn, P J Maudlin, G C KaschnerAbstract:Simulating the forming of anisotropic polycrystals, such as zirconium, requires a description of the anisotropy of the aggregate and the single crystal, and also of their evolution with Deformation (texture development and hardening). Introducing the anisotropy of the single crystal requires the use of polycrystal models that account for inhomogeneous Deformation depending on grain orientation. In particular, visco- plastic self-consistent models have been successfully used for describing strongly anisotropic aggregates. As a consequence, using a polycrystal constitutive law inside finite element (FE) codes represents a considerable improvement over using empirical constitutive laws, since the former provides a physically based description of anisotropy and its evolution. In this work we develop a polycrystal constitutive description for pure Zr deforming under quasi-static conditions at room and liquid nitrogen temperatures. We use tensile and compressive experimental data obtained from a clock-rolled Zr sheet to adjust the constitutive parameters of the polycrystal model. Twinning is accounted for in the description. The polycrystal model is implemented into an explicit FE code, assuming a full polycrystal at the position of each integration point. The orientation and hardening of the individual grains associated with each element is updated as Deformation Proceeds. We report preliminary results of this methodology applied to simulate the three-dimensional Deformation of zirconium bars deforming under four-point bend conditions to maximum strains of about 20%. A critical comparison between experiments and predictions is done in a second paper (Kaschner et al., Acta mater. 2001, 49(15), 3097-3107). Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.
Simon Pauly - One of the best experts on this subject based on the ideXlab platform.
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Stability of the B2 CuZr phase in Cu-Zr-Al-Sc bulk metallic glass matrix composites
Journal of Alloys and Compounds, 2019Co-Authors: B. Escher, Ivan Kaban, Uta Kühn, Jürgen Eckert, Simon PaulyAbstract:Abstract This study investigates the effect, that replacing Zr in a glass-forming Cu47.5Zr47.5Al5 alloy by Sc (0–2 at.%) has on the phase formation as well as on the thermal and mechanical properties. Even though it is not reflected in the thermal data, the glass-forming ability (GFA) is significantly reduced. This originates from the increased tendency to precipitate the shape-memory phase B2 CuZr(Sc), which, in turn, promotes the formation of bulk metallic glass (BMG) matrix composites. Sc appears to be very effective in stabilizing the B2 crystals because it forms the stable B2 CuSc phase with a similar lattice constant like B2 CuZr. By adjusting the casting parameters, the composite microstructure of Cu47.5Zr46.5Al5Sc1 can be controlled to a certain extent. The yield strength and the plasticity of the present composites depend on the crystalline volume fraction. In-situ high-energy X-ray diffraction reveals that Deformation Proceeds in three stages: (i) martensitic transformation of the B2 phase, (ii) yielding of the amorphous phase and continuing martensitic transformation, (iii) completion of the phase transformation and plastic Deformation of all phases. Our work suggests that Sc is a promising candidate to adjust the microstructure and, thus, the mechanical properties of CuZr-based composites consisting of a glassy matrix and shape-memory crystals.
S Van Petegem - One of the best experts on this subject based on the ideXlab platform.
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the effect of stress triaxiality on the phase transformation in transformation induced plasticity steels experimental investigation and modelling the transformation kinetics
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2021Co-Authors: Efthymios Polatidis, G N Haidemenopoulos, D Krizan, N Aravas, Tobias Panzner, Miroslav Smid, Ioanna Papadioti, Nicola Casati, S Van PetegemAbstract:Abstract In situ multiaxial loading during neutron diffraction tests were undertaken on a low-alloyed Quenched and Partitioning (QP the amount of Deformation-induced martensite is similar under uniaxial and equibiaxial tension but it is significantly smaller under tension/compression. The transformation kinetics are modeled using a recently developed kinetic model that accounts for the stress state and the stability and size of the austenite particles. The larger austenite particles transform first and the mean volume of the austenite particles decreases with increasing strain; the decreasing austenite particle size impedes the phase transformation as the Deformation Proceeds. It is concluded that stress triaxiality alone cannot account for the differences in the transformation kinetics between different loading states and that the number of potential nucleation sites depends on the stress state.
N Aravas - One of the best experts on this subject based on the ideXlab platform.
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the effect of stress triaxiality on the phase transformation in transformation induced plasticity steels experimental investigation and modelling the transformation kinetics
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2021Co-Authors: Efthymios Polatidis, G N Haidemenopoulos, D Krizan, N Aravas, Tobias Panzner, Miroslav Smid, Ioanna Papadioti, Nicola Casati, S Van PetegemAbstract:Abstract In situ multiaxial loading during neutron diffraction tests were undertaken on a low-alloyed Quenched and Partitioning (QP the amount of Deformation-induced martensite is similar under uniaxial and equibiaxial tension but it is significantly smaller under tension/compression. The transformation kinetics are modeled using a recently developed kinetic model that accounts for the stress state and the stability and size of the austenite particles. The larger austenite particles transform first and the mean volume of the austenite particles decreases with increasing strain; the decreasing austenite particle size impedes the phase transformation as the Deformation Proceeds. It is concluded that stress triaxiality alone cannot account for the differences in the transformation kinetics between different loading states and that the number of potential nucleation sites depends on the stress state.
R C Reed - One of the best experts on this subject based on the ideXlab platform.
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on the origin of creep dislocations in a ni base single crystal superalloy an ecci ebsd and dislocation dynamics based study
Acta Materialia, 2016Co-Authors: Zhuangming Li, Stefan Zaefferer, Seyed Masood Hafez Haghighat, Dierk Raabe, R C ReedAbstract:Abstract This work investigates the origin of creep dislocations in a Ni-base, single crystal superalloy subject to creep at an intermediate stress and temperature. Employing high angular resolution electron backscatter diffraction (HR-EBSD), electron channeling contrast imaging under controlled diffraction conditions (cECCI) and discrete dislocation dynamics (DDD) modelling, it is shown that low-angle boundaries—which correspond to dendrite boundaries or their residues after annealing—are not the major sources of creep dislocations. At the onset of creep Deformation, they are the only active sources. Creep dislocations are emitted from them and percolate into the dislocation-depleted crystal. However, the percolation is very slow. As creep Deformation Proceeds, before the boundary-originated dislocations move further than a few micrometers away from their source boundary, individual dislocations that are spread throughout the undeformed microstructure become active and emit avalanches of creep dislocations in boundary-free regions, i.e. regions farther than a few micrometer away from boundaries. Upon their activation, the density of creep dislocations in boundary-free regions soars by two orders of magnitude; and the entire microstructure becomes deluged with creep dislocations. The total area of boundary-free regions is several times the total area of regions covered by boundary-originated creep dislocations. Therefore, the main sources of creep dislocations are not low-angle boundaries but individual, isolated dislocations in boundary-free regions.