The microstructure and corrosion resistance of biological Mg-Zn-Ca alloy processed by high-pressure torsion and subsequently annealing

Magnesium alloy has great potential for bone implantation. However, its corrosion rate is fast in physiological environment. In this paper, biological Mg-Zn-Ca alloy was processed by high pressure torsion (HPT) and subsequently annealed at 90-270 degrees C for 30 min. The microstructure and corrosion resistance in simulated body fluid were investigated. The results revealed that with the rise of the annealing temperature, the grain size of the HPT alloy gradually increased and the relative diffraction peak intensity of (0002) grain orientation decreased. The amount of second phases increased first and then decreased, while the surface stress decreased first and then increased. All of these changes affected the corrosion rate simultaneously. The corrosion resistance of the HPT alloy increased first and then decreased with the rise of annealing temperature. After annealing at 210 degrees C for 30 min, the corrosion resistance was the best. Therefore, it was feasible to control the corrosion rate via annealing treatment.