Optimization of porosity and surface roughness of CMT-P wire arc additive manufacturing of AA2024 using response surface methodology and NSGA-Ⅱ

A novel cold metal transfer and pulse (CMT-P) hybrid arc technology was introduced for additive manufacturing of high-strength aluminum alloy 2024 (AA2024). The effects of process parameters, namely the wire-feed speed, travel speed, and CMT/P ratio (ratio of number of CMT stages to pulse stages in a cycle), on the porosity and surface roughness of AA2024 CMT-P additive manufacturing were systematically investigated using the response surface methodology and an improved non-dominated sorting genetic algorithm (NSGA). The results showed that the wire-feed speed had the greatest effect on the porosity and surface roughness. The porosity initially decreased and then increased with an increase in the wire-feed speed. However, the surface roughness decreased with an increase in the wire-feed speed. Moreover, the porosity was reduced with a decrease in the travel speed. With an increasing travel speed, the surface roughness initially decreased and then increased. Furthermore, for both porosity and surface roughness, the best results were obtained at a CMT/P ratio of 1/4. Thus, high porosity and surface roughness in the additive-manufactured parts were caused by high values of wire-feed speed, travel speed, and CMT/P ratio. In addition, using the optimized process parameters, additive parts with low porosity and low surface roughness could be produced.