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

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 x 10(-4) s(-1) to 1.28 x 10(-3) s(-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 beta-Li phase, and the alpha-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 alpha-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 x 10(-3) s(-1). This was proposed to be resulted from the interaction between slips and alpha-Mg grains, whichwas quite different from the serrated effect explained by the dynamic strain aging (DSA) mechanism. (C) 2015 Elsevier Ltd. All rights reserved.