Microstructure Optimization and Strength-Ductility Synergy by Heat Input Regulation in Wire-Arc Additively Manufactured 7055 Al Alloy
摘要
Wire-arc additive manufacturing (WAAM) of Al-Zn-Mg-Cu alloys components offers significant potential for aerospace applications. However, metallurgical defects control and regulation of microstructure and properties have emerged as the critical bottlenecks that limit its further development. This study employed a custom-designed 7055 aluminum alloy welding wire in conjunction with cold metal transfer (CMT) WAAM technology to investigate the effect of deposition parameters on microstructure and mechanical properties, and underlying mechanisms were systematically elucidated. The results indicate that deposition parameters significantly influence molten pool behavior by modulating heat input. At low voltage (11.1 V), fine equiaxed grains formed, whereas at a higher voltage (17.5 V), grain coarsening occurred, accompanied by mixed microstructure comprising both equiaxed and columnar grains. After T6 heat treatment, the strength of all specimens increased by approximately 260% compared to as-deposited counterparts. Among them, 2# specimen (130 A, 11.1 V) exhibited the best comprehensive mechanical properties, with tensile strength of 577 MPa and elongation of 14%. The combination of equiaxed grains, low porosity, and uniformly distributed η′ (Mg (Zn, Cu)2) phase were identified as the key factors underlying its excellent performance. In addition, fine and dispersed pores are less detrimental to ductility, whereas high porosity can induce stress concentration and suppress the formation of dimples. By identifying rational deposition parameters, this study provides a theoretical foundation and experimental data to support manufacturing of high-performance WAAM 7xxx series aluminum alloy components.