ZA27合金中杂质对合金耐蚀性能的影响

Grain boundary segregation of impurity elements and its effect on corrosion resistance in ZA27 alloy

根据分子动力学理论建立了熔体ZA27合金的原子集团,结合计算机编程构造出ZA27合金α相与熔态合金共存时的原子模型及α相大角度晶界模型.利用递归法计算了杂质Cd、Pb、Sn元素固溶于晶粒内,处于固体/熔体相界面及其在α相晶界处的环境敏感镶嵌能.研究结果表明:杂质Cd、Pb、Sn处于固体/熔体相界区的能量最低,固溶于晶粒内的能量最高,说明杂质Cd、Pb、Sn在α相内溶解度很小,结晶时富集于固体/熔体相界前沿熔体中,从而导致凝固结束后杂质Cd、Pb、Sn元素偏聚于晶界,这会降低合金的耐蚀性.

A model of ZA27 cast alloy melt was set up by molecular dynamics theory. The atomic structural model of the solid-liquid interface and the high-angle grain boundary model of α phase in ZA27 were constructed by computer programming. The environment-sensitive embedding energy （ESE）of impurity atom（Cd, Pb, Sn）inside grain, at grain boundary and solid-liquid interface was calculated by recursion method. The results show that the environment-sensitive embedding energy （ESE）is the lowest when impurity is at the solid-liquid interface, and the highest when inside grain. It means that the solid solubility of impurity elements in α phase is very small, and during solidification the impurity elements are enriched in the melt near solid-liquid interface, which leads to reduces corrosion resistance of the alloy. the segregation of impurity atoms at grain boundaries and reduces corrosion resistance of the alloy.