Improving the microstructure and mechanical properties of ultralight Mg-Li-Zn alloy by multidirectional asymmetric rolling

Abstract

In this work, a multi-pass asymmetric rolling of Mg-8Li-1Zn alloy with four different directional routes were carried out with a diameter ratio of 1:1.08 for the upper and lower rolls, and the deformation of the rolling processes were analyzed by finite element simulation. The effects of asymmetric rolling routes on microstructure, mechanical properties, and stress-strain of the Mg-Li alloy were investigated in detail. Results reveal that the thickness of α-Mg phase (≈47 µm) in the annealed alloy is significantly refined (≈12 µm) and distributed in the matrix as lamellar. The ultimate tensile strength (UTS) reaches up to 336.7 MPa by the forward rolling (FR), while the alloy still possesses an ultra-high elongation (18.38%) by the turned-reverse rolling (TRR) and a good combination of UTS (≈310 MPa) and elongation (≈14.51%) in the turned rolling (TR). This is attributed to the multidirectional asymmetric rolling which results in different cross-shear areas. Additionally, the magnitude and direction of the shear force produced during rolling have different effects on the activation of the slip system within the dual-phase alloy.