Cyclic deformation behaviors of AZ31B magnesium alloy in two different asymmetric loading manners

The low cycle fatigue (LCF) behavior of AZ31B magnesium alloy with fiber texture was investigated in two asymmetric loading manners with strain ratios of Rε=0 (named as T-T loading manner) and Rε=-∞(named as C-C loading manner), respectively. It was found that {10-12}<10-11> extension twinning-detwinning occurred in the samples in both the manners. Although the characteristics of twinning-detwinning alternations in the two manners exhibited little difference, the mechanical behaviors were quite different. Detwinning was induced during tensile unloading in the T-T manner and resulted in an evident Bauschginer effect, and cyclic softening in the tension was observed. The LCF life in this case was 68 cycles. In contrast, cyclic hardening occurred in both the tension and compression in the C-C manner with a life of 53 cycles. The twinning-detwinning contribution to the plastic strain-range was reduced especially in the C-C manner. The difference of twinning-detwinning contribution to the plastic strain-range between the two loading manners was responsible for the different LCF lives.