Gradient microstructure and strength-ductility synergy improvement of 2319 aluminum alloys by hybrid additive manufacturing

Wire-arc additive manufacturing (WAAM) technology has been considered as a suitable method for manufacturing large components of aluminum alloys due to its high deposition rate and material utilization. However, the coarse grain size, high porosity and poor mechanical properties of as-deposited aluminum alloys have limited their further development. In this study, a novel hybrid additive manufacturing (HAM) technology combining WAAM and friction stir processing (FSP) has been developed, and a gradient microstructure 2319 aluminum alloy with ultrafine grains-equiaxed grains-columnar grains was successfully fabricated. The microstructure evolution and mechanical properties also have been investigated in this study. The grain size distribution, texture analysis, and the percentage of recrystallized grains were characterized by electron backscatter diffraction (EBSD). The experimental results demonstrated that the hybrid additive manufacturing can achieve a substantial grain refinement (87.09%) and increase the dynamic recrystallization content to 62% due to alternating mechanical and thermal effects. Meanwhile, compared with WAAM specimens, the hybrid-manufactured 2319 aluminum alloy has improved yield strength (YS) by 32.22%, ultimate tensile strength (UTS) by 8.75%, and elongation (EL) by 20%. The dominant mechanism of the significant strength-ductility synergy improvement also has been revealed.