Degradation behavior of Ca–Mg–Zn intermetallic compounds for use as biodegradable implant materials

• Degradation behavior of Ca–Mg–Zn compounds was examined as biodegradable material.
• Degradation rate could be reduced by the formation of intermetallic compounds.
• Degradation rate could be varied by Zn content in the IM1 phases.
• Formability of Zn oxide was found to control the corrosion behavior of IM1 phases.

With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca–Mg–Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15 − x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6 h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250 h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions.