为了提高铝合金表面的力学性能, 利用同轴送粉器将高纯度的Cr, Fe, Co, Ni, Cu粉末激光沉积在铝合金表面, 制备了AlCrFeCoNiCu高熵合金涂层。以激光功率、扫描速度、送粉率为因子, 以润湿角、稀释率为响应, 综合田口分析与逼近理想值分析(TOPSIS)对激光沉积工艺参数进行多目标优化。利用XRD、SEM和EDS技术分析了涂层的相结构、微观组织和元素含量, 并对涂层进行了显微硬度测试。采用优化后的工艺参数进行实验验证, 最优值接近度C*i由0538 9增加到0.567 4, 提高了5.28%, 最佳工艺参数为激光功率1 300 W, 扫描速度120 mm/min, 送粉率5.4 g/min。沉积层为FCC和BCC相结构; 显微组织包括柱状晶、等轴晶, 在枝晶间出现Cu偏析; 涂层的平均硬度为509 HV0.2, 是基材的5倍。结果表明: 综合利用田口分析和TOPSIS的方法可有效优化铝合金表面激光沉积高熵合金的工艺参数, AlCrFeCoNiCu高熵合金涂层可以显著改善铝合金表面的力学性能。

To improve the mechanical properties of an aluminum alloy surface, high-purity Cr, Fe, Co, Ni, and Cu powders were laser deposited on the alloy by using a coaxial powder feeder to form an AlCrFeCoNiCu High-Entropy Alloy (HEA) coating. With laser power, scanning speed, and powder feeding rate selected as the factors and the wetting angle and dilution taken as the responses, a multi-objective optimization of the process parameters of laser deposition was conducted by combining the Taguchi method and the technique for order preference by similarity to an ideal solution (TOPSIS). The phase structure, microstructure, and element contents were analyzed by XRD, SEM and EDS, and the surface hardness of the coating was determined. The results of the validation experiments reveal that the relative closeness coefficient (C*i) increased by 5.28% from 0.538 9 to 0.567 4 and that the ideal parameter values were laser power of 1 300 W, scanning speed of 120 mm/min, and powder feed rate of 5.4 g/min. During laser deposition, the HEA coating consisted of body-centered cubic and face-centered cubic phases , and the microstructure of the coating is composed of columnar and equiaxed crystals. Segregation of copper occurred in indendrites , and the average hardness of the coating is 509 HV0.2, which is five times that of the substrate. These results indicate that combination of the Taguchi method and TOPSIS can effectively optimize the process parameters of laser deposition of HEA on aluminum alloys and that AlCrFeCoNiCu HEA coating can significantly improve the mechanical properties of aluminum alloys.