The Experts below are selected from a list of 13302 Experts worldwide ranked by ideXlab platform
A.d. Sheikh-ali - One of the best experts on this subject based on the ideXlab platform.
-
Grain Boundary Sliding: Theory
Reference Module in Materials Science and Materials Engineering, 2016Co-Authors: A.d. Sheikh-aliAbstract:This article highlights dislocation mechanisms of Grain Boundary Sliding (GBS) in plastic deformation range. Several different cases are considered: GBS along coincidence boundaries coupled to Boundary migration and GBS along general boundaries, which is not intrinsically linked to Boundary migration; GBS along smooth and steps (or ledges) containing boundaries operating with and without intragranular slip.
-
The influence of crystallographic texture on Grain Boundary Sliding during superplastic deformation in Zn–1.1%Al alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: A.d. Sheikh-aliAbstract:Abstract Textured Zn–1.1%Al alloy which pole figure is characterized by two 0 0 0 2 components has been subjected to superplastic deformation in different directions. One of the straining directions is favorable for basal slip and the other is not. The contribution of Grain Boundary Sliding to total deformation has been estimated on the basis of measurements of the vertical component of Sliding. The material shows significant anisotropies of flow stress and Grain Boundary Sliding. Deformation in the direction unfavorable for intragranular slip results in a much higher flow stress and the contribution of Grain Boundary Sliding to the total strain than deformation in the favorable direction. These results demonstrate an independent relationship between Grain Boundary Sliding and intragranular slip during superplastic flow.
-
The effect of Grain Boundary Sliding on curvature-driven Boundary migration in Zn bicrystals
Scripta Materialia, 2007Co-Authors: A.d. Sheikh-aliAbstract:Zinc bicrystals with an originally flat 89° symmetric tilt Boundary tilted at 44° to the tensile direction were strained at high-temperature. Crystallographic slip in Grains was suppressed by the special geometry of the bicrystals. Grain Boundary Sliding significantly increases the amount of capillarity-driven Boundary migration which tends to turn the Boundary normal to the free surfaces. The results are interpreted in terms of the reduced Boundary mobility, which is sensitive to Grain Boundary Sliding. The Sliding can increase the reduced mobility by an order of magnitude.
-
On the independent behavior of Grain Boundary Sliding and intragranular slip during superplasticity
Materials Science Forum, 2001Co-Authors: A.d. Sheikh-ali, Hamid GarmestaniAbstract:Operation of Grain Boundary Sliding is examined for conditions of plastic strain incompatibility that is the most frequent case for deformation of polycrystals. Two coexisting components of Grain Boundary Sliding: dependent and independent on intragranular slip are distinguished. Theoretical estimate of a ratio between slip induced Sliding and intragranular slip is obtained. It is concluded that at the beginning of deformation intragranular slip and Grain Boundary Sliding behave independently. However, at high strains they can be viewed to some extent as interdependent processes.
-
On the Relationship Between Grain Boundary Sliding and Intragranular Slip During Superplastic Deformation
MRS Proceedings, 1999Co-Authors: A.d. Sheikh-ali, Jerzy A. Szpunar, Hamid GarmestaniAbstract:This paper examines Grain Boundary Sliding under the conditions of plastic strain incompatibility that is the most frequent case in polycrystalline materials. Two components of Grain Boundary Sliding: dependent and independent on intragranular slip are distinguished. Theoretical estimate of a ratio between slip induced Sliding and intragranular slip is obtained. It is concluded that slip and Sliding are rather independent than interrelated processes.
Yashashree Kulkarni - One of the best experts on this subject based on the ideXlab platform.
-
Rate dependence of Grain Boundary Sliding via time-scaling atomistic simulations
Journal of Applied Physics, 2017Co-Authors: Farah Hammami, Yashashree KulkarniAbstract:Approaching experimentally relevant strain rates has been a long-standing challenge for molecular dynamics method which captures phenomena typically on the scale of nanoseconds or at strain rates of 107 s−1 and higher. Here, we use Grain Boundary Sliding in nanostructures as a paradigmatic problem to investigate rate dependence using atomistic simulations. We employ a combination of time-scaling computational approaches, including the autonomous basin climbing method, the nudged elastic band method, and kinetic Monte Carlo, to access strain rates ranging from 0.5 s−1 to 107 s−1. Combined with a standard linear solid model for viscoelastic behavior, our simulations reveal that Grain Boundary Sliding exhibits noticeable rate dependence only below strain rates on the order of 10 s−1 but is rate independent and consistent with molecular dynamics at higher strain rates.
Hiroyuki Muto - One of the best experts on this subject based on the ideXlab platform.
-
Direct measurements of Grain Boundary Sliding in yttrium-doped alumina bicrystals
Applied Physics Letters, 2003Co-Authors: Katsuyuki Matsunaga, Hiroyuki Muto, Hitoshi Nishimura, T Yamamoto, Yuichi IkuharaAbstract:The behavior of Grain Boundary Sliding in pure and yttrium-doped Al2O3 was directly measured at a high temperature, using bicrystal experiments. For this purpose, we fabricated Al2O3 bicrystals containing a random Grain Boundary with or without yttrium ions. High-resolution transmission electron microscopy observations and energy dispersive x-ray spectroscopy analyses showed that bicrystals were successfully joined at an atomic scale, and doped yttrium ions segregated along the Grain boundaries. It was found by compressive creep tests that the Grain Boundary Sliding rate was restrained by two orders of magnitude due to yttrium addition, as compared to that of undoped bicrystals.
-
Grain-Boundary Sliding and Interlocking of Two-Phase Ceramics
Materials Science and Engineering Serving Society, 1998Co-Authors: Hiroyuki MutoAbstract:Publisher Summary The aim of this chapter is to examine the Grain-Boundary Sliding and interlocking at high temperatures of two-phase ceramics. The Dryden-Kucerovsky-Wilkinson-Watt theory (DKWW) is extended to the viscoelastic deformation associated with Grain-Boundary Sliding and interlocking of elastic Grains embedded in a contiguous viscous matrix. A two-phase model-ceramic in creep deformation acts as a non-Newtonian fluid, which has the viscosity with creep-strain-hardening. The constitutive relation between the strain rate and the creep strain is utilized to determine the viscosity, volume fraction of intergranular melt, and the equilibrium creep strain for Grain interlocking.
Farah Hammami - One of the best experts on this subject based on the ideXlab platform.
-
Rate dependence of Grain Boundary Sliding via time-scaling atomistic simulations
Journal of Applied Physics, 2017Co-Authors: Farah Hammami, Yashashree KulkarniAbstract:Approaching experimentally relevant strain rates has been a long-standing challenge for molecular dynamics method which captures phenomena typically on the scale of nanoseconds or at strain rates of 107 s−1 and higher. Here, we use Grain Boundary Sliding in nanostructures as a paradigmatic problem to investigate rate dependence using atomistic simulations. We employ a combination of time-scaling computational approaches, including the autonomous basin climbing method, the nudged elastic band method, and kinetic Monte Carlo, to access strain rates ranging from 0.5 s−1 to 107 s−1. Combined with a standard linear solid model for viscoelastic behavior, our simulations reveal that Grain Boundary Sliding exhibits noticeable rate dependence only below strain rates on the order of 10 s−1 but is rate independent and consistent with molecular dynamics at higher strain rates.
Mototsugu Sakai - One of the best experts on this subject based on the ideXlab platform.
-
The large-scale deformation of polycrystalline aggregates: cooperative Grain-Boundary Sliding
Acta Materialia, 2000Co-Authors: H Muto, Mototsugu SakaiAbstract:The mechanisms and processes of large-scale deformation of polycrystalline materials are examined using model aggregates comprising circular or hexagonal bars. It is emphasized that cooperative Grain-Boundary Sliding is essential to allow large-scale deformation, contradicting the conventional models for the superplastic deformation of polycrystalline materials which proceed with the Sliding process via switching respective Grains. Theoretical considerations of the effects of Grain size and shape, Grain-Boundary phase, and of the dimension of test specimen on the cooperative Grain-Boundary Sliding are made.
