Effect of heat treatment on mechanical and biodegradable properties of an extruded ZK60 alloy

- The strength and corrosion resistance of ZK60 alloys are improved by T5 treatment due to the formation of small and uniformly distributed MgZn phases.
- After T6 treatment, certain amount of MgZn2 phase is precipitated along the grain boundary which deteriorates the corrosion resistance.
- The as-extruded ZK60 exhibits the worst corrosion resistance. The content of ZnZr phase is high in the second phase.

ZK60 magnesium alloy possess good mechanical properties and is a potential biodegradable material. But its high degradation rate is not desirable. In this study the effect of heat treatment on the biodegradable property of ZK60 alloy was investigated. T5 treated, T6 treated, as-cast and as-extruded ZK60 alloys were studied. Microstructure characterization, electrochemical measurement and immersion test were carried out. The results showed that both the mechanical properties and degradation behavior were improved after T5 treatment due to the formation of small and uniformly distributed MgZn phases. The as-cast alloys also exhibited good corrosion resistance. However, the as-extruded and T6 treated samples were severely corroded due to the formation of large amounts of second phases accelerating the corrosion rate owing to the galvanic corrosion. The corrosion resistance of ZK60 alloy was as following: T5 treated > as-cast > T6 treated > as-extruded.

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