AZ91D镁合金表面热扩渗膜层的结构及性能研究

Investigation on Microstructures and Properties of AZ91D Mg Alloy Surface Thermal Diffusion Layer

采用真空固体粉末热扩渗法,对AZ91D镁合金表面实施Al-Zn及Al-Zn-Nd共渗处理。对扩散合金层进行显微组织形貌和物相组成分析,并在3.5%NaCl溶液中测量镁合金基体及其扩渗试样的耐腐蚀性能。结果表明,在385℃下恒温热扩散10 h,能在试样表面获得一定厚度的连续均匀的渗层,且Al-Zn-Nd共渗层组织比Al-Zn共渗层组织更加细小致密;Al-Zn共渗的膜层主要由Mg_(17)Al_(12)、Al_5Mg_(11)Zn_4和α-Mg三相构成,而Al-Zn-Nd共渗的膜层主要由Mg_(17)Al_(12)、Al_5Mg_(11)Zn_4、NdAl_3和α-Mg四相构成;扩渗处理明显改善了AZ91D镁合金的耐蚀性,且Al-Zn-Nd共渗试样的耐蚀性优于Al-Zn共渗试样。

Al-Zn and Al-Zn-Nd treatment on AZ91D Mg alloy sueface was conducted by vacuum solid powder thermal diffusion. The microstructure and phase composition of the diffusion layer were analysed, the corrosion resistance of Mg alloy substrate and diffusion samples in 3.5%NaCI solution were measured. The results show that constant thermal diffusion at 385 ℃ for 10 h can get a certain thickness coating which is uniform and dense on the sample surface, and Al-Zn-Nd diffusion layer＇s tissue is more denser and smaller than Al-Zn diffusion layer＇s. The Al-Zn diffusion layer is mainly composed of Mg17Al12, Al5Mg11Zn4 and α-Mg, while Al-Zn-Nd diffusion layer is composed of Mg17Al12, Al5Mg11Zn4, NdA13 and ct-Mg. Vacuum solid powder thermal diffusion obviously improves the corrosion resistance of AZglD Mg alloy, and the corrosion resistance of A1-Zn-Nd thermal diffusion sample is better than that of Al-Zn thermal diffusion sample.