A precipitation-tailoring paradigm for nucleation control: breaking the efficiency ceiling of Mg-Zr grain refiner

A breakthrough improvement in grain refinement efficacy of Mg-Zr refiner of greater than 70% relative to commercial counterparts is achieved by regulating nano-scale Zr precipitation. Re-melting generates Zr-saturated halos, while subsequent rolling induces lattice defects that promote Zr nucleation during heating. This yields dual-scale Zr particles: submicron precipitates (100–500 nm) within halos and nano-particles (20–40 nm) in α-Mg grains. The treated refiner simultaneously provides abundant heterogeneous nucleants and enhanced constitutional supercooling, establishing it as the most effective Mg-Zr grain refiner reported to date. This study provides a novel paradigm for designing high-efficiency refiners through nano-scale precipitation regulation.