Mg–1Zn–1Ca alloy for biomedical applications. Influence of the secondary phases on the mechanical and corrosion behaviour

Abstract

An as-cast Mg–1Zn–1Ca alloy has been soundly characterized to be used as a biodegradable material in biomedical applications. Ca and Zn additions have a great influence in the microstructure, mechanical properties and corrosion behaviour of Mg alloys. SEM examinations revealed that most of the Ca and Zn atoms form Mg 2 Ca and Ca 2 Mg 6 Zn 3 precipitates, which distribute preferentially along the grain boundaries forming a continuous network of secondary phases. The results of nanoindentation tests show differences in hardness and elastic modulus between the α-Mg matrix and the secondary phases. The results of three-point bending tests shows that cracks propagate following the network formed by the intermetallic compounds at the grain boundaries (GBs). The evolved hydrogen after immersion in Hank’s solution of the alloy has been also estimated, showing a change in the corrosion mechanism after 160 h. The intermetallic compounds act as a barrier against corrosion, so that it progresses through the α-Mg matrix phase. • Mg–1Zn–1Ca alloy is formed by α-Mg matrix and Mg 2 Ca and Ca 2 Mg 6 Zn 3 secondary phases. • Fracture mechanism occurs along the continuous secondary phases in a brittle way. • Mg–1Zn–1Ca alloy shows proper mechanical properties for biomedical applications. • Mg 2 Ca and Ca 2 Mg 6 Zn 3 secondary phases act as barriers for corrosion progress. • Immersion in Hank’s solution produces Mg(OH) 2 and HA as corrosion products.