Comprehensive study on the differences in microstructure and mechanical properties of Mg-Li alloy fabricated by additive manufacturing, casting, and rolling

Abstract

In order to explore the forming mechanism of direct energy deposition of magnesium-lithium alloy wire with high lithium content, this study introduces a novel approach utilizing Cold Metal Transfer Wire Arc Additive Manufacturing (CMT-WAAM) to successfully fabricate thin-walled structures of LA103Z Mg-Li alloy. A comprehensive comparison was conducted to evaluate the microstructure and mechanical properties of different regions on CMT-WAAM samples, in addition to cast and rolled samples. The microstructure of CMT-WAAM samples is mainly composed of β-Li phase and fine needle shaped α-Mg phase, exhibiting a notable divergence from the microstructure observed in cast and rolled samples. It is noteworthy that the mechanical properties along the deposition direction exhibited significant variability in CMT-WAAM samples, but no significant anisotropy is discerned in the mechanical properties along the deposition and scanning directions. The discrepancies in mechanical properties across different regions are predominantly attributed to variations in grain size, and the size and proportion of the α-Mg phase and secondary phases, which are related to the low heat input and high cooling rate of the CMT-WAAM process. The mean tensile strength of CMT-WAAM samples is 159.5 MPa, marking a respective increase of 30.7% and 13.9% compared to cast and rolled samples. These findings underscore the outstanding strength of CMT-WAAM samples compared to conventionally formed samples. This study provides novel insights into additive manufacturing of dual-phase Mg-Li alloys for large-scale complex structures.