Effect of extrusion parameters on degradation of magnesium alloys for bioimplant applications: A review

Abstract

Magnesium alloys, as a new generation temporary biomaterial, deserve the desirable biocompatibility and biodegradability, and also contribute to the repair of the damaged bone tissues. However, they do not possess the required corrosion resistance in human body fluid. Hot mechanical workings, such as extrusion, influence both the mechanical properties and bio-corrosion behavior of magnesium alloys. This review aims to gather information on how the extrusion parameters (extrusion ratio and temperature) influence the bio-corrosion performances of magnesium alloys. Their effects are mainly ascribed to the alteration of extruded alloy microstructure, including final grain size and uniformity of grains, texture, and the size, distribution and volume fraction of the second phases. Dynamic recrystallization and grain refinement during extrusion provide a more homogeneous microstructure and cause the formation of basal texture, resulting in improved strength and corrosion resistance of magnesium alloy. Extrusion temperature and extrusion ratio are reported as the influential factors in the degradation. The reports reveal that the increase in extrusion ratio and/or the reduction in extrusion temperature cause a decrease in the final grain size, leading to intensification of basal texture, in parallel side of the samples with extrusion line, and to lower volume fraction and size of precipitates in magnesium alloys. These all lead to improving the bio-corrosion resistance of the magnesium alloy implants.