Effect of Multi-Directional Forging on Microstructure and Mechanical Properties of Dual-Phase Mg-8Li-3Al-0.3Si Alloy

The Mg-8Li-3Al-0.3Si dual-phase alloy (LA83-0.3Si) was subjected to six multi-directional forging (MDF) passes in the present work, then its microstructure, mechanical properties, and work hardening and work softening effects were examined and analyzed. The results indicate that the continuous dynamic recrystallization (CDRX) mechanism of the LA83-0.3Si dual-phase alloy gradually transitioned to a discontinuous dynamic recrystallization (DDRX) mechanism as the temperature increased after MDF. This temperature change induced a transition in the basal texture from bimodal to multimodal, significantly reducing the texture intensity and weakening the alloy's anisotropy. At 310 °C, the AlLi phase nucleated into coated particles to stabilize the structure. Additionally, the increase in the forging temperature weakened the synergistic deformation capability of the α/β phases, while the hardening behavior of the β-Li phase provided a nucleation pathway for dynamic recrystallization (DRX). MDF significantly enhanced the strength and ductility of the LA83-0.3Si alloy. The alloy's strength continued to rise, while elongation decreased as the forging temperature increased. The ultimate tensile strength (UTS) and elongation (EL) reached 267.8 MPa and 11.9%, respectively. The work hardening effect increased with the forging temperature, whereas the work softening effect continuously diminished, attributed to the enhanced hardening behavior of the β phase and the reduced ability to transfer dislocations.