Study on heat treatment to improve the microstructure and corrosion behavior of ZK60 magnesium alloy

The effects of different heat treatments on the microstructure and corrosion behavior of an as-cast ZK60 magnesium alloy were investigated by microscopic analyses, weight loss tests, hydrogen evolution tests, and electrochemical measurements. The results indicate that solution treatment (T4) could result in the dissolution of most of the second-phase particles and make the alloying elements (Zn and Zr) distribute uniformly. However, new tiny second phase particles re-precipitated during aging treatment (T6). The as-cast and heat-treated ZK60 alloys displayed filiform-like corrosion morphologies with different initiation and propagation features in the early corrosion period, and they gradually developed corrosion pits. Their corrosion rates showed similar change tendencies, and the T4-treated ZK60 alloy exhibited the best anti-corrosion performance owing to it having the weakest micro-galvanic effect. The relationship between the alloys’ microstructures and their corrosion features was analyzed, and the involved mechanism was examined.