Reducing the cyclic tension-compression asymmetry and cyclic hardening of ZK61 magnesium alloy via the compression-extrusion process

Abstract

In order to reduce the cyclic tension-compression asymmetry and cyclic hardening that exists widely in magnesium alloys, ZK61magnesium alloys with different texture intensities and grain sizes were fabricated by conventional extrusion and compression-extrusion process. It was found that the compression-extrusion process had a remarkable effect on the texture weakening and grain refining, which significantly improved monotonic tension-compression asymmetry and cyclic tension-compression asymmetry. Under their combined effects, the {10–12} twinning-detwinning behavior of ZK61 magnesium alloy during cyclic tension-compression deformation was effectively suppressed, resulting in a remarkable reduction of the difference of peak stresses in tension and compression. In the meantime, shape asymmetry embodied in a concave-up characteristic of the cyclic hysteresis loops was almost eliminated as the weakening of the detwinning-prismatic slip transition. Twinning-promoted dislocation pile-up and twinning-induced grain segmentation were significantly attenuated with texture weakening and grain refining, leading to a substantial weakening of cyclic hardening. Eventually, ZK61 magnesium alloy with low cyclic tension-compression.