Effects of Mn Addition on the Microstructure and Mechanical Properties of As-cast and Heat-Treated Mg-Zn-Ca Bio-magnesium Alloy

摘要

The effects of manganese (Mn) addition on the microstructure, tensile properties and hardness of the as-cast (AC) and heat-treated (HT) Mg-2Zn-0.5Ca-xMn (x = 0.5, 1.0 and 1.5 wt%) alloys were investigated for biomedical osteosynthesis applications. The transformation of the microstructure and precipitation of the AC and HT alloys with different Mn additions were analyzed by optical microscope, x-ray diffraction, scanning electron microscope and transmission electron microscope. Mechanical properties of the alloys were tested on an electronic universal testing machine and a micro-hardness tester. The results showed that the polygonal α-Mn precipitate was the existing form of Mn in the alloys, which was attached by Mg-Zn phases. With increasing the Mn addition, the grains in the AC Mg-2Zn-0.5Ca-xMn alloys became more refined, and changed from bulky and uneven dendrite crystal to uniform equiaxed crystal. Meanwhile, the MgZn_2 and Mg_2Zn_3 phases increased in HT alloys with the increase in Mn addition. Moreover, the Strength and elongation of the AC and HT alloys both decreased after reaching a peak with the increase in Mn addition. The HT Mg-2Zn-0.5Ca-1 .0Mn alloy also possessed the optimal tensile strength of 205 MPa and the elongation of 15.7% among the alloys in this study.