Quantitative Revealing of Reversed Tension-Compression Yield Asymmetry of an Extruded Mg-Gd-Y-Zn-Zr Alloy

Abstract

An extruded Mg-8.5Gd-2.5Y-0.5Zn-0.3Zr (wt%) alloy, containing a prismatic texture with basal plane vertical to extrusion direction, exhibits a reversed yield asymmetry (RYA). In-situ synchrotron diffraction measurement and polycrystal plasticity simulation were employed to gain quantitative revealing on this asymmetric behavior. Under tension, macro yield is associated with plasticity in most grains via basal slip, prismatic slip and tensile twinning, making contributions of 44%, 34% and 22%, respectively. Under compression, the initial yield stage involves with plasticity in some grains and elasticity in the prismatic textured grains. This “composite effect” associated with elasticity enhances the yield strength. At later stage, slip is activated in the prismatic textured grains, making contributions of 16%. The stronger strain hardening of dislocation than the other dislocations can also enhance strength. So the RYA is due to the varied deformation behavior under tension and compression, resulting from the existence of prismatic textured grains.

Keywords: Magnesium alloys, Yield asymmetry, Synchrotron radiation, Simulation