Microstructural evolution and mechanical properties of Mg–Zn–Y–Sn alloy during ultrasonic vibration assisted ECAP

Ultrasonic vibration assisted equal-channel angular pressing (UVA-ECAP) has been widely adopted across diverse alloy systems for its ability to enhance forming efficiency and tailor microstructures. A systematic investigation is carried out to determine the effects of UVA-ECAP on Mg-Zn-Y-Sn alloy microstructure and mechanical performance. Experimental results demonstrate that the addition of trace Sn suppresses dendritic solidification and promotes grain refinement. The as-cast Mg-4Zn-12Y-0.3Sn alloy exhibits an ultimate tensile strength of 348.71 MPa and an elongation of 16.01%. Under UVA-ECAP, both strength and ductility increase with vibration amplitude, reaching 460 MPa and 21.23%, respectively. Concurrently, abundant {10 3} twins and {10 1}–{10 2} double twins are generated. With increasing amplitude, continuous dynamic recrystallization (CDRX) becomes dominant, leading to a higher fraction of fine equiaxed grains. During deformation, the LPSO-matrix interfaces accumulate geometrically necessary dislocations, forming subgrain zones that provide both rigid load sharing and preferred nucleation sites, whereas Sn 3 Y 5 particles furnish dispersed Zener pinning and damage suppression. Their synergy under ultrasonic loading produces a refined, uniform recrystallized matrix with a stabilized dislocation substructure, enabling concurrent gains in strength and ductility.