Effect of trace copper on the microstructure, corrosion behavior and biological properties of biodegradable Mg–2Zn-1Gd-0.5Zr alloy

Abstract

The biodegradable Mg–2Zn-1Gd-0.5Zr-xCu (x = 0, 0.1, 0.3, 0.5 wt.%) alloys are prepared to evaluate their microstructures, corrosion behavior, biocompatibility and antimicrobial properties. When the Cu element adds to the alloys, the new MgZnCu phase generates in the alloys in addition to the MgZn2 phase, W–Mg3Gd2Zn3 phase and I–Mg3Gd6Zn phase. With the Cu content increases, the grains become finer. Meanwhile, the shape of the MgZnCu phase transforms from spherical and elongated into the reticular. The grain boundary, the reticular W–Mg3Gd2Zn3 phase and the MgZnCu phase act as physical barriers to hinder the spread of corrosion. The generation of Ca–P compounds and the formation of dense oxides further improve the corrosion resistance of the alloys. Meanwhile, an increase in the content of the second phase and a change in the morphology of the MgZnCu phase also enhance galvanic corrosion, which reduces the corrosion resistance of the alloys. The corrosion rate of the Mg–2Zn-1Gd-0.5Zr-0.1Cu alloy is 0.47 ± 0.05 mm/year, and its degradation rate is much lower than that of the other Cu-containing alloys. Mg–2Zn-1Gd-0.5Zr-0.1Cu alloy has no cytotoxicity to MC3T3-E1 in the biocompatibility tests and shows good antibacterial properties in the antimicrobial experiments. In general, the Mg–2Zn-1Gd-0.5Zr-0.1Cu alloy is considered as the potential biodegradable antimicrobial biomaterial for bone implants.

Keywords

• Mg alloy
• Copper
• Microstructure
• Biological properties
• Corrosion