Fiber laser welding characteristics of the butt welded joint of novel ultralight Mg-10.1Li-3.1Al-2.9Zn alloy

The novel ultralight material Mg-10.1Li-3.1Al-2.9Zn alloy (Mg-Li alloy) of which the density is about half that of pure magnesium has a wide application prospect in various industrial fields, while its weldability is rarely investigated. This study explored the fiber laser welding of 5 mm-thick Mg-Li alloy in butt-welding configuration through a L₁₆ (4³) orthogonal experiment design. The microstructures of the base metal and the joint obtained under the optimum condition were observed. The results showed that the strengthening precipitates in base metal were τ ₁ (Li₈MgSi₆), τ ₃ (Li₂MgSi) and MgLiAl₂ with a size in several microns and nano-sized AlLi, while that in fusion zone were nano-sized Li_0∼0.9Mg₂Si and MgLiAl₂. The tensile strength of the welded joint was equivalent to that of BM while the impact toughness and plasticity slightly reduced. It was found that the corrosion resistance of fusion zone with the single-phase matrix (β-Li) was about 3.2 times that of BM with the dual-phase matrix (α-Mg + β-Li). The results provided guiding significance for the popularization and application of the novel ultralight material Mg-Li alloy in industry.