This study investigated the effects of multi-directional compression (MDC) on the microstructure and mechanical properties of a solution-treated Mg-2Y-Ni (at.%) alloy. With increasing compression passes, the coarse blocky LPSO phases underwent a process involving kinking, tearing, and final fracture. The acicular LPSO phases, due to their significantly different load-bearing capacities along different orientations, primarily deformed via fracture. Furthermore, {10 \(\overline{1 }\) 2} tensile twins and a high density of substructures were formed during the MDC process. The results indicate that the alloy subjected to 15 compression cycles under a stress of 210 MPa exhibits the optimum combination of mechanical properties, achieving an ultimate compressive strength (UCS) of 401 MPa, a compressive yield strength (CYS) of 243.5 MPa, and a failure strain (εf) of 16%. The enhancement in mechanical properties is primarily attributed to grain refinement, the kinking and refinement of LPSO phases, and the formation of substructures. The stable plastic deformation in the later stages of compression is associated with extensive kinking of LPSO phases, grain refinement, activation of <c+a> dislocations, and the presence of low-angle grain boundaries (LAGBs). This work provides a strategy for enhancing the mechanical properties of Mg-RE alloys containing LPSO phases at low cost.
