Effect of loading modes on torsional behavior of an extruded Mg alloy bar

Abstract

The torsional deformation with shear stress is crucial for improving mechanical performance of wrought Mg alloys. Consequently, the difference of mechanical behavior between fixed-end and free-end torsion was investigated. It is found that strain hardening behavior is affected by end constraint. The decreased hardening rate is exhibited which is dominated by prismatic slip during fixed-end torsion. For free-end loading, two stages of strain hardening are presented during torsion, i.e., constant hardening rate and slowly decreased hardening rate. The basal slip dominates the onset of plastic deformation. The prismatic slip becomes dominated mechanism at large shear strain. However, the axial effect is sensitive to forward and reversal torsion. The difference of axial stress between forward and reversal torsion under fixed-end is attributed to twin growth. The difference of axial strain is small during forward and reversal torsion under free-end, which is attributed to the activation of tensile twinning.