Anisotropic Mechanical Behavior in an Extruded AZ31 Magnesium Alloy: Experimental and Crystal Plasticity Modeling

Abstract

The mechanical anisotropy on extruded AZ31 magnesium alloy bar has been investigated by combining experimental measurement and crystal plasticity modeling. Monotonic tension and compression are conducted in four loading directions with the oblique angle φ of 0°, 30°, 60° and 90° from extrusion radial direction to extrusion direction, and are also simulated by visco-plastic self-consistent model with considering twinning and detwinning scheme at the first time. The simulation results are well in agreement with the corresponding experimental data. Combined with the Schmid factor (SF), the anisotropic mechanical behaviors including yield strength, ultimate strength and strain hardening rate are interpreted with the predicted relative activities of deformation modes, texture evolution and twin volume fraction. With the loading angle varying from 0° to 90°, it is found that prismatic slip becomes the primary deformation mode with the decreasing relative activities of basal slip and extension twinning in tension. While the deformation mechanism is more complex in compression: Extension twinning gets great activation at the beginning of the deformation, especially under compression along 90°; basal slip and pyramidal < c + a > slip dominate the late deformation of compression along 0° and 30°, while basal slip and prismatic slip are dominated modes in compression along 60° and 90°. Additionally, different \(\{{{10}\stackrel{{-}}{1}{{2}}}\}\) twinning behaviors with two or three and one or two pairs of twin variants being activated in tension along 30° and compression along 90°, respectively, have a close correlation with the texture evolution to coordinate plastic deformation. The activation of \(\{{{10}\stackrel{{-}}{1}{{2}}}\}\) twinning, which varies with the loading angle φ, results in the increased trend of strain hardening rate. Following the exhausting of twinning, non-basal slips with the highest SF become the primary deformation mode subsequently, contributing to the decreasing trend in hardening behavior and the anisotropy of ultimate strength.