Microstructure and deformation behaviors of two Mg–Li dual-phase alloys with an increasing tensile speed

Abstract

Two duplex Mg–Li alloys, Mg–8.02Li–0.210Y and Mg–8.43Li–0.353Ymm (Y-rich mischmetal) alloys, were prepared by casting method with a permanent metal model. Microstructures, mechanical properties and deformation behaviors at tensile rates from 1.28×10−4s−1 to 1.28×10−3s−1 were evaluated. The results showed that when increasing the tensile speed, the strength increased with a decreasing elongation. The strength and ductility of Mg–8.02Li–0.210Y alloy were more sensitive to the tensile speed. Fracture occurred mainly in the β-Li phase, and the α-Mg phase participated into fracture at relatively high tensile speeds, which led to the strength increase of both alloys with the increment of tensile speed. Long-stripe-like α-Mg grains in Mg–8.02Li–0.210Y alloy hindered the fracture and resulted in a higher elongation. Mg–8.02Li–0.210Y alloy presented a serrated effect at a relatively high initial rate of 1.28×10−3s−1. This was proposed to be resulted from the interaction between slips and α-Mg grains, which was quite different from the serrated effect explained by the dynamic strain aging (DSA) mechanism.