Microstructural evolution and dynamic strain aging (DSA) of Mg-6%Gd-1%Zn alloy during tension and compression testing at intermediate temperatures

Abstract

The Mg-6%Gd-1%Zn alloy exhibits flow serrations when strained at intermediate temperatures due to the dynamic strain ageing phenomenon. Such flow serrations during deformation need the simultaneous and competitive movement of diffusing solutes and mobile dislocations. Although the alloy examined has a random texture, tension-compression asymmetry and significantly greater yield stress and work hardening in compression than in tension have been observed. During deformation at intermediate temperatures, and independently of the nature of the stress (tension or compression), the activation of -dislocations and tensile twin systems has been observed. The volume fraction of twins is always higher, however, in the case of compression testing. At the intermediate temperatures where flow serrations are observed, Gd and Zn atoms pin dislocations as well as twins. Above 250 °C, the flow serrations disappear and g´ and g´´ precipitates form in the basal plane which increase work hardening.