(上海交通大学 金属基复合材料国家重点实验室，上海 200240)
摘 要: 采用AlCl3-NaCl熔盐，在较低温度(380 ℃)下对AZ91D镁合金表面进行热扩散渗铝处理，制备一扩散合金层。采用金相显微镜、扫描电子显微镜、X射线能量色散仪、X射线衍射仪，对所得的扩散合金层的组织和结构进行分析；采用纳米压痕仪分析表面合金层的硬度；采用交流阻抗及极化曲线分析在3.5%(质量分数)NaCl溶液中进行熔盐冶金扩散处理前、后AZ91D镁合金的耐腐蚀性能。结果表明：AZ91D镁合金经熔盐冶金扩散处理后，在较低温度下，即可获得连续致密的表面合金层；合金层主要由外层的Mg2Al3与内层的Mg17Al12金属间化合物组成，该表面合金层的形成伴随着熔盐中置换反应及扩散过程的发生；合金层显著提高合金的表面硬度，并明显改善AZ91D镁合金在3.5%(质量分数)NaCl溶液中的耐腐蚀性能。
关键字: AZ91D镁合金；熔盐；扩散；硬度；耐蚀性
aluminizing coating on surface of AZ91D Mg alloy
（State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China）
Abstract:The aluminizing of AZ91D Mg alloy by AlCl3-NaCl molten salts at a lower temperature of 380 ℃ were investigated, and a diffusion alloyed layer was prepared. The microstructure and composition of the diffusion alloyed layer were studied by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffractometry. The nano-hardness of the alloyed layer was studied by nanoindentation. The corrosion resistance of the treated AZ91D Mg alloy was evaluated in 3.5% (mass fraction) NaCl solution by electrochemical impedance spectroscopy and potentiodynamic polarization. The results show that a continuous and dense alloyed layer can be formed on the surface of the AZ91D Mg alloy by aluminizing in molten salts at low temperature. The aluminum-alloyed layer consists mainly of Mg2Al3 and Mg17Al12 intermetallic layers. The formation of the Mg-Al alloyed layer is associated with a displacement reaction mechanism and diffusion process that takes place during the molten salt treatment. The alloyed layer substantially improves the hardness as well as the corrosion resistance of the AZ91D Mg alloy, which is attributed to the high volume fraction of intermetallic compounds in the surface alloyed layer.
Key words: AZ91D Mg alloy; molten salt; diffusion; hardness; corrosion resistance
