(南華大學 機械工程學院，衡陽 421001)
摘 要: 利用激光熔覆技術在AZ91鎂合金表面制備Al-30%Cu(質量分數)合金涂層。采用X射線衍射儀、掃描電子顯微鏡、顯微硬度儀、電化學工作站表征分析激光熔覆試樣的組織和性能。結果表明:激光熔覆層與基體呈現出良好的冶金結合，無明顯的氣孔裂紋等缺陷。其中，熔覆區(qū)出現大量的牙齒狀、花瓣狀和細顆粒狀組織，結合區(qū)為典型的樹枝晶組織。XRD結果表明:熔覆層主要由二元相Mg17Al12、AlMg、CuMg2和三元相Al2CuMg、Mg32Al47Cu7組成。由于晶粒細化和新形成的金屬間化合物的共同作用，合金熔覆層的顯微硬度平均值(392.2HV)為AZ91鎂合金基體硬度(約70HV)的5.6倍。熔覆層的腐蝕電位比基體的提高179.2 mV，腐蝕電流密度較基體的降低兩個數量級，耐蝕性得到較大的改善。
關鍵字: AZ91鎂合金；Al-Cu合金涂層；激光熔覆；顯微硬度；耐蝕性
（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
