扩渗时间对镁合金表面扩渗Zn+La2O3组织与性能的影响

在390℃温度下对AZ31镁合金进行固态扩渗Zn+La2O3（扩渗剂中的质量分数为0.4%）处理，扩渗时间分别为0、2、4、6h。研究了不同扩渗时间下镁合金表面渗层组织的变化，并测试了镁合金表面扩渗层的硬度和耐腐蚀性能。结果表明：当扩渗时间为2h时，未出现渗层；当扩渗时间为4h时，扩渗层中出现了Mg0.97Zn0.03固溶体和Mg-Zn化合物(MgZn+Mg2Zn3+MgZn2+ Mg2Zn11)。随着扩渗时间的延长，使得Zn原子的扩渗能力增强，Mg和Zn反应扩散形成了多种化合物，在AZ31镁合金表面得到了渗层。当扩渗时间为6h时，Mg7Zn3作为一种新相出现在了渗层中，同时，渗层组织粗化。扩渗试样的硬度随扩渗时间的增加而增加，而耐腐蚀性能在扩渗时间为4 h时为最佳。

Effect of Expansion Time on Microstructure and Properties of Zn+La2O3 Coating on Magnesium Alloy

AZ31 magnesium alloy surface was carried out solid diffusion Zn+La2O3(the mass fraction of La2O3 in the diffusion agent was 0.4%) treatmentat 390 °C, the diffusion time was 0,2, 4 and 6h respectively.The changes of the surface microstructure of magnesium alloy at different times of diffusion were studied. The surface hardness and corrosion resistance of the magnesium alloy were tested. The results show that no diffusion layer appeared when the diffusion time was 2 h. solid solution Mg0.97Zn0.03 andMg-Zn compounds(MgZn+Mg2Zn3+MgZn2+ Mg2Zn11) appeared on the diffusion layer when the diffusion time was 4 h. With the prolonged diffusion time, Zn atom diffusion ability was enhanced and variouscompoundswere formed by Mg and Zn reaction. The diffusion layer was obtained on AZ31 magnesium alloy surface.When the expansion time was 6 h, Mg7Zn3 as a new phase was present in diffusion layer, the microstructure of diffusion layer became coarse at the same time. The hardness increaseedwith the increase of the diffusion time, and the corrosion resistance was optimal when the diffusion time was 4 h.