(南华大学 机械工程学院，衡阳 421001)
摘 要: 利用激光熔覆技术在AZ91镁合金表面制备Al-30%Cu(质量分数)合金涂层。采用X射线衍射仪、扫描电子显微镜、显微硬度仪、电化学工作站表征分析激光熔覆试样的组织和性能。结果表明:激光熔覆层与基体呈现出良好的冶金结合，无明显的气孔裂纹等缺陷。其中，熔覆区出现大量的牙齿状、花瓣状和细颗粒状组织，结合区为典型的树枝晶组织。XRD结果表明:熔覆层主要由二元相Mg17Al12、AlMg、CuMg2和三元相Al2CuMg、Mg32Al47Cu7组成。由于晶粒细化和新形成的金属间化合物的共同作用，合金熔覆层的显微硬度平均值(392.2HV)为AZ91镁合金基体硬度(约70HV)的5.6倍。熔覆层的腐蚀电位比基体的提高179.2 mV，腐蚀电流密度较基体的降低两个数量级，耐蚀性得到较大的改善。
关键字: AZ91镁合金；Al-Cu合金涂层；激光熔覆；显微硬度；耐蚀性
（School of Mechanical Engineering, University of South China, Hengyang 421001, China）
Abstract:Al-30%Cu (mass fraction) alloy coating was prepared by laser cladding on AZ91 magnesium alloy. The microstructure and properties of the laser cladding specimen were characterized by several advanced techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and electrochemical workstation. The results show that the cladding layer is well bonded with the substrate, and no obvious defects, such as pores and cracks, are visible. There are a large number of tooth-shaped, petal-like and granular precipitates dispersed in the laser cladding zone, while a typical dendritic microstructure occurs in the bonding zone. The XRD results show that the laser cladding layer is composed of binary phases Mg17Al12, AlMg and CuMg2, and as well as ternary phases Al2CuMg and Mg32Al47Cu7. Due to the fine-grain strengthening and newly-formed intermetallics, the average microhardness of the cladding layer is 392.2 HV, which is about 5.6 times higher than that of the AZ91 substrate (about 70 HV). The corrosion potential (φcorr) increases 179.2 mV and the corrosion current decreases by two orders of magnitude. The corrosion resistance of the AZ91 substrate is greatly improved.
Key words: AZ91 magnesium alloy; Al-Cu alloy coating; laser cladding; microhardness; corrosion resistance
