Degradation behavior of the as-extruded and ECAP-processed Mg–4Zn alloy by Ca addition and hydrothermal coating

Abstract

Coating is an effective approach to address the high corrosion rate of biodegradable Mg alloys, as their main challenge toward their extensive use. In this regard, it was tried to control the degradation process of an Mg–4Zn alloy by Ca addition, equal channel angular pressing (ECAP), and hydrothermal coating. The obtained results indicated that excellent grain refinement induced by Ca incorporation and ECAP simultaneously, improved both mechanical strength and corrosion resistance of the Mg-based substrate. The achieved grain refinement resulted in a thicker, more compact and integrated coating, where the ECAP-processed Mg–4Zn–0.5Ca alloy exhibited the best coating quality with no penetrative cracks. The ECAP-coated Mg–4Zn–0.5Ca alloy benefits from both the improved coating quality and superior substrate corrosion resistance, leading to a noticeable improvement in corrosion resistance. This emphasizes the positive role of Ca addition and ECAP process in promoting the mechanical properties and degradation behavior of Mg–4Zn substrate, as well as the quality of hydrothermally-synthesized coating.

Keywords

• Biodegradable Mg alloys
• Coating
• Corrosion rate
• ECAP
• Mechanical properties
• Mg–Zn–Ca