Induced growth orientation deviation of Mg(OH)₂ by heat treatment to enhance corrosion resistance of Mg-Sc alloy

This work presents a novel microstructure-driven strategy to enhance the corrosion resistance of Mg-Sc alloys by regulating the growth orientation deviation of Mg(OH)₂ corrosion products through heat treatment. This approach promotes the formation of dense and compact corrosion films, fundamentally improving the barrier performance. Results reveal that aging induces a transition from randomly stacked Mg(OH)₂ to a highly ordered, interleaved lamellar structure, significantly improving corrosion resistance. The stress-relieved condition exhibits a partially ordered morphology with intermediate protection, while solution-treated alloys suffer from severe grain coarsening and develop porous, disordered corrosion films. The growth orientation deviation is governed by the combined effects of grain refinement, texture weakening, nanoscale precipitate pinning, and reduced surface energy anisotropy. These factors collectively promote lateral stacking of corrosion products, enhancing film compactness and corrosion resistance. This study provides a microstructure-driven strategy to control corrosion product growth orientation, offering a new pathway for developing highly corrosion-resistant Mg alloys.