Deformation behavior of Mg–Zn–Zr magnesium alloy on the basis of macro-texture and fine-grain size under tension and compression loading along various directions

Abstract

The deformation behavior of an extruded Mg–Zn–Zr alloy in the form of plate/sheet was investigated on the basis of fine-grained and initial macro-texture along various directions under uniaxial compression and tension test. The initial macro-texture revealed that 60.4% of grains have c-axes of hexagonal closed packed crystal structure along the normal direction and 17.4% grains have c-axes parallel to the transverse direction. The results showed that the flow stress and strain hardening rate under compression and tension were significantly affected by the loading directions and the initial texture. The ratio of tensile yield strength to the compressive yield strength along normal direction extruded direction, and transverse direction was found 0.85, 1.5, and 0.93, respectively. The practically symmetric yielding behavior along normal and transverse direction was caused by the fine-grained size, twinning dependencies on strain path loading, and texture. The anisotropy ∼1.5 along extrusion direction is the cause of the large fraction of {101¯2}<101¯1> extension twinning under compression and no twinning activity in tension along ED in the early stages of deformation in large grains. The strain hardening curves under tension and compression shows almost similar behavior in the normal direction. For extrusion direction and transverse direction, strain hardening curves exhibited three and two regimes under compressive loading which leads to a large difference in ultimate compressive and tensile strength. It is also revealed that {101¯2}<101¯1> extension twinning was favorable, while {101¯1}<101¯2> contraction twinning and {101¯1}−{101¯2} double twinning were unfavorable for strain hardening. The underlying deformation mechanisms under different loading paths were discussed on the basis of X-ray diffraction and optical microscopic analysis.