Chen L, Bin Y, Zou W, et al. The influence of Sr on the microstructure, degradation and stress corrosion cracking of the Mg alloys - ZK40xSr.[J]. Journal of the Mechanical Behavior of Biomedical Materials, 2016, 66:187.
发布日期: 2016-01-05 发布者: 郑洋 阅读: 21

   Abstract:In the present work, new magnesium (Mg) alloys (Mg-4Zn-0.6Zr-xSr, x=0, 0.4, 0.8, 1.2, 1.6<ce:hsp sp=0.25/>wt%; ZK40xSr) were prepared and studied as potential biodegradable materials. The influence of strontium (Sr) addition on the properties of the new Mg alloys was investigated, which included microstructure, corrosion degradation, and the stress corrosion cracking (SCC) susceptibility. The average grain size of the ZK40Sr was approximately 100<ce:hsp sp=0.25/>μm, which was significantly smaller than that of ZK40 alloy without Sr (402.3±40.2<ce:hsp sp=0.25/>μm). The size of grain boundaries precipitates in the ZK40xSr alloys gradually increased with the increase of Sr content. The grain boundaries finally showed a continuously distribution and net-like shape. The degradation test showed that the average degradation rate of the ZK40xSr alloys increased with the increase of Sr addition. In the case of Mg-4Zn-0.6Zr, the degradation rate was 2.2<ce:hsp sp=0.25/>mg<ce:hsp sp=0.25/>cm -2 <ce:hsp sp=0.25/>day -1 , which was lower than that of Mg-4Zn-0.6Zr-1.6<ce:hsp sp=0.25/>Sr (4.93<ce:hsp sp=0.25/>mg<ce:hsp sp=0.25/>cm -2 <ce:hsp sp=0.25/>day -1 ). When the ZK40xSr alloys were immersed in m-SBF, the rod-like Sr-contained hydroxyapatite (HA) substance was detected, which was known to enhance cell growth around bone implants. The fracture surfaces of the as-cast Mg-4Zn-0.6Zr-1.6Sr were shown intergranular stress corrosion cracking (IGSCC) patterns. The increase of SCC susceptibility of the higher Sr ZK40xSr alloys was attributed to the increase of micro-galvanic corrosion between the α-Mg and the grain boundaries precipitates. The SCC susceptibility values were ≈0.13 and ≈0.41 for the Mg-4Zn-0.6Zr-0.4Sr and the Mg-4Zn-0.6Zr-1.6Sr, respectively. ;