Effects of deep cryogenic treatment on microstructure, mechanical, and corrosion of ZK60 Mg alloy

This study aims to investigate the effects of deep cryogenic treatment combined with traditional heat treatment on the microstructural characteristics, mechanical properties, and corrosion performance of ZK60 magnesium alloy. Quasi-in-situ TEM testing also indicates that deep cryogenic treatment induces the formation of ultra-fine zinc-rich precipitates in the magnesium matrix. After solid solution treatment, materials with cryogenic treatment will retain significant internal stress, which promotes the subsequent precipitation of rod-like β′₁ during aging. Microstructural analysis reveals that deep cryogenic treatment before solution treatment and artificial aging can significantly enhance the length and density of rod-like β′₁ precipitates. The treated material shows improved strength while maintaining its original elongation rate. Due to the nanoscale precipitation-induced micro galvanic effect, the aged samples exhibit a higher corrosion rate. The abundance of micrometer-sized second phases in the untreated sample does not significantly accelerate the material's corrosion rate. The solution-treated samples show the weakest micro galvanic effect and the best corrosion resistance.