微量Sr对Mg-0.2Zn-0.1Mn-xSr医用可降解镁合金显微组织、力学性能及腐蚀性能的影响

Effects of trace Sr on microstructure, mechanical properties and corrosion resistence of Mg-0.2Zn-0.1Mn-xSr biomaterials

摘要:

本文主要研究在Mg-0.2Zn-0.1Mn中添加微量的Sr后，Mg-0.2Zn-0.1Mn-xSr（x=0.1、0.2、0.3）合金显微组织、力学性能及耐腐蚀性能的变化。显微组织观察结果表明随着Sr含量增加，晶粒尺寸明显降低；Mg17Sr2相在镁基体中呈颗粒状均匀弥散分布，且Mg17Sr2相体积随着Sr含量增加而长大。室温拉伸试验结果表明微量的Sr能够提高镁合金的抗拉强度和屈服强度，但延伸率却表现出下降的趋势。通过Kokubo模拟体液中的浸泡实验了解镁合金的降解行为。失重实验测得Mg-0.2Zn-0.1Mn-xSr (x=0，0.1，0.2，0.3)腐蚀速率为：6.85、6.01、6.80和7.52mm/a。微量Sr的添加能够提高镁合金的耐腐蚀性能；但随着Sr含量增加，镁合金更容易产生点蚀和晶间腐蚀，反而使镁合金耐腐蚀性能出现降低。这是因为添加微量Sr后镁合金晶粒细化，细小而弥散分布的Mg17Sr2相有助于腐蚀产物膜沉积形成对基体的保护，使得镁合金更耐蚀。而过大的Mg17Sr2相会加剧局部的微电偶腐蚀，破坏腐蚀产物膜，降低镁合金的耐腐蚀性能。结果表明Mg-0.2Zn-0.1Mn-0.1Sr具有最佳的力学性能和耐腐蚀性能配比。

Abstract:

In this work, the effects of adding trace Sr elements on microstructure, mechanical properties and corrosion properties of Mg-0.2Zn-0.1Mn-xSr(x=0, 0.1, 0.2, 0.3 wt. %) alloys were investigated. The result of microstructure observation reveal that the grain size of the alloy decreases with the increase of Sr. The granular Mg17Sr2 phase is uniformly dispersed in the magnesium matrix. While, the second phase grows up as the Sr increases. The result of mechanical properties investigated by tensile test at room temperature indicated that micro Sr can improve the yield strength and tensile strength. But the elogations decreased with the increase of Sr. Degradation was studied using immersion tests in Kokubo solution. The corrosion rates were faster and the pitting was more likely to occur when the Sr increased. The average corrosion rates of Mg-0.2Zn-0.1Mn-xSr(x=0, 0.1, 0.2, 0.3 wt. %) that measured by weight loss were 6.85→6.01→6.80→7.52mm/a. Trace Sr can improve the corrosion resistance of magnesium alloys. However, with the increase of Sr content, the magnesium alloys are more prone to pitting and intergranular corrosion, which in turn reduces the corrosion resistance of magnesium alloys. The bio-corrosion behaviors can be attributed to the grain refinement and the diffused second phase, which can promote the formation of corrosion product film. However, the bigger second phase in the matrix will accelerate the local corrosion，which will reduce the corrosion resistance of magnesium alloy. The results show that Mg-0.2Zn-0.1Mn-0.1Sr has the best mechanical properties and corrosion resistance.