Achieving superior strength and plasticity in cold metal transfer plus pulse wire arc additive manufacturing of a novel Al-Si-Mg-Cu-Zn alloy via in-situ laser remelting

Al-Si-Mg alloys are widely used in aerospace and automotive industries due to their excellent casting properties and wear resistance. However, a key challenge in wire arc additive manufacturing of Al-Si-Mg alloys is the presence of metallurgical defects and inferior mechanical properties, areas that have received limited attention in existing research. Critical factors impacting performance include the porosity in deposited layers and the formation of columnar grains caused by high energy input. This study explores the application of interlayer laser remelting to a novel Al-Si-Mg-Cu-Zn alloy produced via the Cold Metal Transfer plus Pulse (CMT-P) process and provides a comprehensive analysis of their microstructure, mechanical properties, and strengthening mechanisms. The findings reveal that interlayer laser remelting significantly reduces porosity, suppresses the growth of columnar grains, and promotes the formation of equiaxed grain zones with a higher density of low-angle grain boundaries. Furthermore, the laser-affected zone generated during remelting results in finer and denser precipitates, thereby effectively enhancing the mechanical properties. Notably, the CMT-P+2.2 kW laser-remelted samples demonstrate an average ultimate tensile strength of 373.48 +/- 0.51 MPa, yield strength of 267.33 +/- 9.61 MPa, and an elongation of 11.3 +/- 0.5 %, reflecting improvements of 29.24 %, 42.6 %, and 11.5 %, respectively, compared to the CMT-P samples. The study also analyzed the effects of four strengthening mechanisms during the laser remelting process, identifying precipitation strengthening and solid solution strengthening as the most significant contributors to the enhanced performance of the Al-Si-Mg-Cu-Zn alloy. This research presents an innovative and feasible approach for fabricating Al-Si-Mg-Cu-Zn alloys with excellent mechanical properties through additive manufacturing.