Designing low-density, high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment. This study proposes an interpretable machine learning strategy to simultaneously enhance the mechanical properties and corrosion resistance of Mg-Li alloy. Key alloy factors (KAFs) influencing ultimate tensile strength (UTS), elongation (EL), and corrosion rate (CR) were identified through alloy factor construction and screening. Using KAFs and processing parameters as inputs, gradient boosting regression models for UTS, EL, and CR were established, achieving the coefficients of determination of test-set above 0.85. Then, SHapley Additive exPlanations (SHAP) analysis quantified the impact of KAFs, and an element evaluation method was established to identify Al, Si, Ca, and Zn as candidates for alloy design. Finally, three new alloys were designed via multi-objective optimization. In the hot-extruded state, they exhibited UTS of 253～273 MPa, EL of 18.4%～27.9%, CR of 0.55～1.61 mg/(cm²·day), and ρ of 1.49～1.54 g/cm³. Compared to LAZ103, the new alloys show 34%～44% higher UTS, 35%～79% lower CR, and comparable ρ. Microstructural analysis revealed increased α-Mg, decreased β-Li, reduced coarse secondary phases, and fine Ca-/Si-rich precipitates which are conducive to grain refinement and dislocation density increasing, synergistically enhancing comprehensive property.

Metal additive manufacturing (AM) has been extensively studied in recent decades. Despite the significant progress achieved in manufacturing complex shapes and structures, challenges such as severe cracking when using existing alloys for laser powder bed fusion (L-PBF) AM have persisted. These challenges arise because commercial alloys are primarily designed for conventional casting or forging processes, overlooking the fast cooling rates, steep temperature gradients and multiple thermal cycles of L-PBF. To address this, there is an urgent need to develop novel alloys specifically tailored for L-PBF technologies. This review provides a comprehensive summary of the strategies employed in alloy design for L-PBF. It aims to guide future research on designing novel alloys dedicated to L-PBF instead of adapting existing alloys. The review begins by discussing the features of the L-PBF processes, focusing on rapid solidification and intrinsic heat treatment. Next, the printability of the four main existing alloys (Fe-, Ni-, Al- and Ti-based alloys) is critically assessed, with a comparison of their conventional weldability. It was found that the weldability criteria are not always applicable in estimating printability. Furthermore, the review presents recent advances in alloy development and associated strategies, categorizing them into crack mitigation-oriented, microstructure manipulation-oriented and machine learning-assisted approaches. Lastly, an outlook and suggestions are given to highlight the issues that need to be addressed in future work.