Laser–Direct Current arc Hybrid Additive Manufacturing of Cu-Cr-Zr Alloy: Microstructure Evaluation and Mechanical Properties

Recently, there has been a growing requirement for rapid and cost-effective additive manufacturing solutions for copper alloys with favorable mechanical properties. In this research, laser–direct current arc hybrid additive manufacturing (LAHAM) was employed to fabricate Cu-Cr-Zr alloy. By way of multi-scale characterization including SEM, EBSD and TEM, the effect of scanning speed on the microstructure was systematically investigated in detail. Moreover, an evaluation of mechanical properties was carried out. The results indicated that columnar grains grew across layers with the growth direction tending to the center of the molten pool. When the scanning speed increased from 250 mm/min to 350 mm/min, the proportion of high-angle grain boundaries exceeded 69% and reached a maximum of 79% at 300 mm/min. A large amount of Cr phase was precipitated from the Cu matrix. Both submicron and nanoscale Cr precipitates were observed. Statistically, the area proportion of Cr precipitates was up to 26.3% at 300 mm/min. The changes of heat input and remelting effects were the main reasons for the change in the precipitate level. As a result, the mechanical properties of the Cu-Cr-Zr alloy were enhanced via precipitation strengthening. When the scanning speed was 250 mm/min, the Cu-Cr-Zr alloy sample exhibited an ultimate tensile strength of 311.3 ± 7.8 MPa with an elongation of 38.6 ± 5.6%.