Microstructure, texture, and mechanical properties of Mg-4Zn-1Mn-xCa alloys and the fabrication of biomedical Mg thin-walled micro-tubes

In this study, the microstructure, texture, and mechanical properties of Mg-4Zn-1Mn-xCa (x = 0, 0.2, 0.5, wt%) alloys are studied. The thin-walled micro-tubes of Mg-4Zn-1Mn-xCa (x = 0, 0.2, wt%) alloy are fabricated by hot extrusion, and the microstructure and corrosion behaviors of micro-tubes are investigated. The results show that the addition of trace Ca caused the microstructure of Mg-4Zn-1Mn-xCa alloys to become finer, while resulting in a significant basal texture owing to the increased volume fraction of unrecrystallized grains. Notably, the addition of 0.2Ca enhanced the yield strength (YS) by 30.3%. Then, Mg alloy micro-tubes with an outer diameter of 3.2 mm, inner diameter of 2.4 mm, and a wall thickness of 0.4 mm are successfully produced. Besides, the hardness of micro-tubes with 0.2Ca addition (72.3Hv) is higher significantly than that without Ca addition (62.9Hv), and the grain size is much finer. An electrochemical test demonstrated that the corrosion resistance of micro-tubes shows an improvement with the addition of 0.2Ca. These findings indicated that it is feasible to fabricate a biodegradable Mg stent with grain superfine Mg-4Zn-1Mn-0.2Ca alloy billet.