scholarly journals Statistical Crystal Plasticity Model Advanced for Grain Boundary Sliding Description

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 822
Author(s):  
Alexey Shveykin ◽  
Peter Trusov ◽  
Elvira Sharifullina
Keyword(s):  
Grain Boundary ◽  
Constitutive Model ◽  
Grain Boundaries ◽  
Crystal Plasticity ◽  
Inelastic Deformation ◽  
Grain Boundary Sliding ◽  
Lattice Rotation ◽  
Mutual Arrangement ◽  
Structural Level ◽  
Boundary Sliding

Grain boundary sliding is an important deformation mechanism, and therefore its description is essential for modeling different technological processes of thermomechanical treatment, in particular the superplasticity forming of metallic materials. For this purpose, we have developed a three-level statistical crystal plasticity constitutive model of polycrystalline metals and alloys, which takes into account intragranular dislocation sliding, crystallite lattice rotation and grain boundary sliding. A key advantage of our model over the classical Taylor-type models is that it also includes a consideration of grain boundaries and possible changes in their mutual arrangement. The constitutive relations are defined in rate form and in current configuration, which makes it possible to use additive contributions of intragranular sliding and grain boundary sliding to the strain rate at the macrolevel. In describing grain boundary sliding, displacements along the grain boundaries are considered explicitly, and changes in the neighboring grains are taken into account. In addition, the transition from displacements to deformation (shear) characteristics is done for the macrolevel representative volume via averaging, and the grain boundary sliding submodel is attributed to a separate structural level. We have also analyzed the interaction between grain boundary sliding and intragranular inelastic deformation. The influx of intragranular dislocations into the boundary increases the number of defects in it and the boundary energy, and promotes grain boundary sliding. The constitutive equation for grain boundary sliding describes boundary smoothing caused by diffusion effects. The results of the numerical experiments are in good agreement with the known experimental data. The numerical simulation demonstrates that analysis of grain boundary sliding has a significant impact on the results, and the multilevel constitutive model proposed in this study can be used to describe different inelastic deformation regimes, including superplasticity and transitions between conventional plasticity and superplasticity.

scholarly journals Microstructure Evolution of a High Nb Containing TiAl Alloy with (α2 + γ) Microstructure during Elevated Temperature Deformation

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 916 ◽  
Author(s):  
Yudong Chu ◽  
Jinshan Li ◽  
Lei Zhu ◽  
Yan Liu ◽  
Bin Tang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Temperature Deformation ◽  
Texture Intensity ◽  
Compression Deformation ◽  
Boundary Sliding

In order to verify the correctness of the transition of deformation mechanism with the change in deformation parameters and to reveal the types and mechanism of dynamic recrystallization of γ grains during compression deformation, microstructure characterization of Ti-43.5Al-8Nb-0.2W-0.2B (at. %) alloy after isothermal compression deformation were performed. When the alloy was deformed at 1000 °C/10−2 s−1, the initial γ grains are elongated and significantly refined and the fraction of low angle grain boundaries (LAGB) of γ grains is obviously increased and the texture intensity remains unchanged, which indicates that the compression deformation in dislocation creep region is dominated by intragranular deformation and dynamic recrystallization (DRX) of γ grains. Besides, the lattice rotation at grain boundary serrations may be responsible for the nucleation of new recrystallized γ grains, and the following growth process may be achieved by the migration of γ grain boundaries. However, when the alloy deformed at 1050 °C/10−4 s−1 and 1000 °C/10−4 s−1, the γ grains maintain equiaxed shapes and distribute more uniformly and the fraction of LAGB of γ grains is slightly raised and the texture sharpness decreases, which indicates that the compression deformation in grain boundary sliding (GBS) region is mainly controlled by GBS of γ grains and DRX occurs simultaneously within some coarse γ grains.

Research on Micro-Mechanism of Nanocomposite Ceramic in Two-Dimensional Ultrasound Grinding

2007 ◽  
Vol 359-360 ◽  
pp. 344-348 ◽  
Author(s):  
Bo Zhao ◽  
Yan Wu ◽  
Guo Fu Gao ◽  
Feng Jiao
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Deformation Mechanism ◽  
Ground Surface ◽  
Grain Boundary Sliding ◽  
Second Phase ◽  
Two Dimensional ◽  
Composite Ceramics ◽  
Nano Composite ◽  
Boundary Sliding

Surface microstructure of nano-composite ceramics prepared by mixed coherence system and machined by two-dimensional ultrasonic precision grinding was researched using TEM, SEM, XRD detector and other equipments. Structure, formation mechanism and characteristic of metamorphic layer of ground surface of nano-composite ceramics were researched. The experiment shows micro deformation mechanism of ceramic material in two-dimensional ultrasound grinding is twin grain boundary and grain-boundary sliding for Al2O3, and it is crystal dislocation of enhanced phase, matrix grain boundary sliding, coordination deformation of intergranular second phase as well as its deformation mechanism for nano-composite ceramics. The fracture surfaces of nano-composite materials with different microscopic structure were observed using TEM and SEM. Research shows that ZrO2 plays an important influence on the generation and expansion of crack, and enhances the strength of grain boundaries. When grain boundaries is rich in the ZrO2 particles, the crack produced in grinding process will be prevented, and the surface with plastic deformation will be smooth. The results shows nanoparticles dispersed in grain boundary prevents crack propagation and makes materials fracture transgranularly which makes the processed surface fine.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1193-1209 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Large Strains ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Transient Phenomena ◽  
Boundary Sliding

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

scholarly journals Grain Boundary Sliding and Atomic Structures in Alumina Bicrystals with [0001] Symmetric Tilt Grain Boundaries

2002 ◽  
Vol 43 (7) ◽  
pp. 1561-1565 ◽  
Author(s):  
Tsuyoshi Watanabe ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma ◽  
Hiroyuki Muto ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Atomic Structures ◽  
Symmetric Tilt ◽  
Boundary Sliding

scholarly journals Incompatibility Stresses and Lattice Rotations Due to Grain Boundary Sliding in Heterogeneous Anisotropic Elasticity

2017 ◽  
Author(s):  
Thiebaud Richeton
Keyword(s):  
Finite Element ◽  
Grain Boundary ◽  
Triple Line ◽  
Grain Boundary Sliding ◽  
Boundary Plane ◽  
Lattice Rotation ◽  
Interface Plane ◽  
Grain Boundary Plane ◽  
Analytic Expressions ◽  
Boundary Sliding

Non-uniform grain boundary sliding can induce strain and rotation incompatibilities at perfectly planar interfaces. Explicit analytic expressions of stress and lattice rotation jumps are thus derived at a planar interface in the general framework of heterogeneous anisotropic thermo-elasticity with plasticity and grain boundary sliding. Both elastic fields are directly dependent on in-plane gradients of grain boundary sliding. It is also shown that grain boundary sliding is a mechanism that may relax incompatibility stresses of elastic, plastic and thermal origin although the latter are not resolved on the grain boundary plane. This relaxation may be a driving force for grain boundary sliding in addition to the traditionally considered local shears on the grain boundary plane. Moreover, the obtained analytic expressions are checked by different kinds of bicrystal shearing finite element simulations allowing grain boundary sliding and where a pinned line in the interface plane aims at representing the effect of a triple junction. A very good agreement is found between the analytic solutions and the finite element results. The performed simulations particularly emphasize the role of grain boundary sliding as a possible strong stress generator around the grain boundary close to the triple line because of the presence of pronounced gradients of sliding.

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