A crystal plasticity based approach to establish role of grain size and crystallographic texture in the Tension–Compression yield asymmetry and strain hardening behavior of a Magnesium–Silver–Rare Earth alloy

Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural applications.The present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process annealing.The existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression tests.The yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained counterparts.The impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by Kock–Mecking’s analysis.Crystal plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening behavior.This was especially dominant with coarsening of grain size.Electron Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above simulations.The role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.

Micromechanical Modeling of Elastic-Viscoplastic Behavior of Armco-Fe at High Strain Rate

Heterogeneous dynamical stress-strain response of Armco-Fe was investigated at high strain rates through the Split Hopkinson Pressure Bar （SHPB） testing. It was found that the viscoplastic deformation in BCC ferrite grains is affected by the strain rate. Thermal softening and variation in crystal orientations under high-strain-rate loading were used in the elastic-viscoplastic modeling. The micromechanical analysis with self-consistent transition and homogenization was used for estimation of the global impact response of the material. The results from modeling were found in good agreement with the experimental data.

DEFORMATION OF COPOLYMER MICELLES INDUCED BY AMPHIPHILIC DIMER PARTICLES

Combining self-consistent-field theory and density-functional theory, we systematically study the deformation of copolymer micelles induced by the presence of amphiphilic dimer particles. Due to the amphiphilic nature, dimer particles tend to accumulate onto the interface of the copolymer micelle. With increasing concentration of the symmetric dimer particles, which are made of two identical spherical particles, the micelle deforms from the initial sphere to ellipse, dumbbell, and finally separates into two micelles. Furthermore, asymmetric dimer particles, composed by two particles with different sizes, are considered to investigate the influence of geometry of dimer particles on the deformation of the micelle. It is found that the micelle inclines to deform into dumbbell due to the additional curvature originating in the gathering of asymmetric dimer particles onto the interface of the micelle. The present study on the deformation of micelles is useful to understand the possible shape variation in the course of cell division/fusion.

Electronic States of Some Semiconductor Clusters

Potential surfaces and equilibrium geometries of InAs 2, In 2As, InAs 2 + and In 2As + were studied using the complete active space multi configuration self consistent field (CASMCSCF) technique. Two electronic states, namely 2B 2 and 2B 1, were found to prevail as the ground states for the InAs 2 and In 2As trimers, respectively. The corresponding adiabatic ionization energies were computed and the leading configurations of the ground states were analyzed according to the wavefunctions.