基于NSGA-Ⅱ算法的高熵合金材料激光熔覆形貌的预测和控制方法

Research on the prediction and control method of laser melting morphology of high entropy alloy materials based on NSGA-Ⅱalgorithm

针对激光熔覆AlCoCrFeNiTi合金的成形质量问题,探索工艺参数对稀释率、高宽比和熔覆面积的影响规律,实现熔覆成形质量的预测与优化。采用响应面法建立激光功率、扫描速度、送粉电压与稀释率、高宽比和熔覆面积的数学模型,通过NSGA-Ⅱ遗传算法进行多目标优化。试验结果表明,最优工艺参数为激光功率1770.60 W,扫描速度5.96 mm/s,送粉电压为23.26 V,稀释率、高宽比、熔覆面积的误差分别为6.69%、9.27%、11.96%。稀释率随着激光功率和扫描速度的增大而增大,送粉电压则相反;高宽比及熔覆面积均随着扫描速度增大而减小,送粉电压则相反。该研究结果能为高熵合金熔覆层形貌的预测和控制提供理论依据。

As a new type of material developed in metal materials in recent years,HEAs have large lattice distortion,high configuration entropy,high strength,good toughness,corrosion resistance,high-temperature oxidation resistance,and high temperature softening resistance.In terms of research on high-entropy alloy materials,the existing research mainly focuses on the influences of laser cladding on the structure and properties of high-entropy alloy coatings,rather than process parameters on the forming quality of high-entropy alloy coatings by laser cladding.AlCoCrFeNiTi high-entropy alloy coatings were prepared on AISI 45 steel substrates by laser cladding in the work.Aiming at the forming quality of laser cladding high-entropy alloy materials,the work explored the influences of process parameters on the dilution rate,aspect ratio,and cladding area to predict and optimize the cladding quality.The mathematical model of the process parameters,dilution rate,aspect ratio,and cladding area was established by the response surface methodology(RSM)to analyze the influences of laser power,scanning speed,and powder feeding voltage on the morphology of AlCoCrFeNiTi-coating cladding layer.The RSM can establish a mathematical relationship model between input variables and output quantities.The work used the Box-Behnken design(BBD)module in the RSM,The model of the process parameters and the interaction relationship between the parameters on the response value could be established by the BBD.Besides,multi-objective optimization is performed by the NSGA-Ⅱgenetic algorithm.After optimization,the process parameters are obtained as the laser power of 1,770.60 W,a scanning speed of 5.96 mm/s,and a powder feeding voltage of 23.26 V.The actual value-error ratios of the dilution rate,aspect ratio,and cladding area are verified by experiments to be 6.69,9.27,and 11.96%,respectively.The dilution rate increases with increased laser power and scanning speed and decreases with the increased powder-feeding voltage.The aspect ratio decreases with the increased scanning speed and increased with the increased powder-feeding voltage.With the change of laser power,the aspect ratio first decreased and then increased.The effect of laser power on the cladding area is not significant,and the cladding area decreases with the increased scanning speed and increases with the increased powder-feeding voltage.The maximum microhardness of the HEA clad layer processes with the optimized parameter set is 858.9HV,which is about four times that of the base material(215.8 HV).The AlCoCrFeNiTi HEA clad layer consists of BCC phase and TiC phase,which is consistent with the formation of simple solid solution phase in the HEA clad layer.The HEA clad layer of the optimized parameter group has good metallurgical bonding with the substrate,the coating is dense and the grains are refined.The research results can provide a theoretical basis for the prediction and control of the morphology of highentropy alloy materials prepared by laser cladding.