稀土Gd对SLM成型Mg-Zn-Gd合金耐蚀性能研究

Effect of Gd element on corrosion rate of SLM forming medical magnesium alloy

摘要:

镁合金具有高比强度与良好的生物相容性,是一种理想的骨植入材料。因镁合金降解速率过快在临床应用中受到限制,通过SLM可对其合金化并改善耐蚀性能。利用SLM成型Mg-1Zn-xGd(x=0、0.25、0.5、1、2 wt%)合金,测试镁合金在模拟体液中浸泡72 h平均腐蚀速率变化趋势,采用SEM、EDS与TEM检测手段辅助分析腐蚀机理。实验结果表明,Gd含量对镁合金腐蚀速率影响显著,添加0~2 wt% Gd后镁合金降解速率呈先降低后升高趋势,在添加0.5 wt% Gd时镁合金具有最佳耐腐蚀性能。腐蚀反应产生的表面钝化膜能够一定程度减缓腐蚀的进行,添加过量Gd后沿晶界析出Mg₅Gd相增多加剧了镁合金腐蚀。

关键词:稀土镁合金;耐蚀性能;降解速率;显微组织

Abstract:

Magnesium alloy is an ideal bone implant material with high specific strength and good biocompatibility.SDue to the limitation of rapid degradation rate of magnesium alloy in clinical application, SLM can be used to alloyed magnesium alloy and improve its corrosion resistance.SMg-1zn-xGd (x=0, 0.25, 0.5, 1, 2 wt%) alloy was formed by SLM, and the average corrosion rate of magnesium alloy soaked in simulated body fluid for 72 h was tested. The corrosion mechanism was analyzed by SEM, EDS and TEM.SThe experimental results show that Gd content has a significant effect on the corrosion rate of magnesium alloy, and the degradation rate of magnesium alloy decreases first and then increases with the addition of 0~2 wt% Gd, and the magnesium alloy has the best corrosion resistance with the addition of 0.5 wt% Gd.SThe surface passivation film produced by the corrosion reaction can slow down the corrosion process to a certain extent, and the Mg₅Gd phase precipitated along the grain boundary increases after the addition of excessive Gd, resulting in intensified corrosion of magnesium alloy.

Key words:rare earth Mg alloys; corrosion resistance; degradation rate; microstructure