Effects of Friction Stir Processing on the Microstructure and Properties of Mg–Gd–Nd–Zr Alloy

Friction stir processing (FSP) was adopted as a modification strategy for the Mg–6Gd–3Nd–0.5Zr alloy to address the inherent challenges of coarse grains and insufficient mechanical properties typical of as‐cast rare‐earth magnesium alloys. This study systematically investigates the influence of varying thermo‐mechanical heat inputs (qualitatively evaluated via the ratio of rotational to traverse speed as a relative reference for heat input) on microstructural evolution, second‐phase distribution, and texture characteristics, aiming to elucidate their effects on the alloy's mechanical behavior. Methodologically, the synergy of friction‐induced thermal effects and intense shear strain was utilized to eliminate casting defects, promote the fragmentation of coarse Mg–Gd–Nd eutectic phases into dispersed nanoscale particles, and effectively induce dynamic recrystallization (DRX). Scientifically, the work demonstrates that optimizing these thermo‐mechanical conditions leads to a highly refined and homogenized microstructure, which translates into a well‐balanced enhancement of both strength and ductility. The fundamental mechanisms driving this mechanical improvement is primarily associated with grain refinement, with additional likely contributions from second‐phase dispersion, dislocation accumulation, and texture evolution. Ultimately, this study establishes a comprehensive process–structure–property relationship, providing a robust experimental foundation for the development of high‐performance, structural–functional integrated rare‐earth magnesium alloys.