Improving the mechanical and corrosion properties of pure magnesium by parts-per-million-level alloying

Abstract

Poor cold formability, poor corrosion resistance, and high cost of alloying elements are longstanding barriers to the widespread use of the lightest structural metal, viz. magnesium (Mg). Here, we report that both the room-temperature (RT) stretch formability and corrosion resistance of the commercially used pure Mg could be significantly improved by adding trace amounts of copper (Cu) and calcium (Ca). The mechanical properties were characterized by Erichsen cupping and tensile tests, while the corrosion properties were evaluated by immersion in saline solution. The significant enhancement in the RT stretch formability is associated with the weakened basal texture and refined microstructure, whereas the substantial improvement in the corrosion resistance is related to the strong Fe-removal ability induced mainly by Ca addition and formation of a protective surface film enriched with Cu and Ca. Owing to the trace amounts of the alloying elements, the resultant alloy also showed excellent thermal conductivity, which was almost two times higher than that of the most commonly used Mg alloy (AZ31: Mg–3Al–1Zn in wt.%). These findings are expected to stimulate the development of high-performance Mg alloys that can be used in portable electronic devices, automobile electronics, and household appliances.