Visco-plastic modeling of mechanical responses and texture evolution in extruded AZ31 magnesium alloy for various loading conditions

摘要

Mechanical responses and texture evolution of extruded A231 Mg are measured under uniaxial (tension-compression) and multiaxial (free-end torsion) loadings. Compression loading is carried out in three different directions: along the extrusion direction (ED), perpendicular to the extrusion direction (FED), and 45 degrees to the extrusion direction (45ED) at temperature and strain rate ranges of 77-423 K and 10(-4)-3000 s(-1), respectively. Texture evolution at different intermediate strains reveals that crystal reorientation is exhausted at smaller strains with increase in strain rate while increase in temperature retards twinning. In addition to the well-known tension-compression yield asymmetry, a strong anisotropy in strain hardening response is observed. However, this anisotropy is negligible at smaller strain so that compressive yield stress does not change with loading directions at each temperature and strain rate. Strain hardening during the compression experiment is intensified with decreasing and increasing temperature and strain rate, respectively. Even though the strain hardening response during the free-end torsion experiment resembles that in tension, the shear yield stress is significantly smaller than prediction of von-Mises criterion. This complex behavior is explained through the understanding roles of deformation mechanisms using the Visco-Plastic Self Consistent (VPSC) model. In order to calibrate the VPSC model's constants as accurate as possible, in contrast to previous studies, this paper employs the VPSC model to simulate a vast number of mechanical responses and crystallographic characteristics including stress-strain curves in tension, compression in three directions, and free-end torsion, texture evolution at different strains, lateral strains of compression samples, twin volume fraction, and axial strain during the torsion experiment The modeling results show that depending on the number of measurements used for calibration, roles of different mechanisms in plastic deformation change significantly. (C) 2014 Elsevier Ltd. All rights reserved.