Formability, microstructure and mechanical properties of nano-treated Al-Zn-Mg-Cu alloy fabricated by wire arc additive manufacturing

Wire arc additive manufacturing(WAAM) was utilized to fabricate the nano-treated Al-Zn-Mg-Cu alloy. Effects of fabrication parameters on WAAM formability are systematically investigated. The results show that the nano-treated Al-Zn-Mg-Cu alloy is well formed by alternative path under the following parameters: welding current 190 A, welding speed 350 mm/min, dwell time 90 s. Post-deposition heat treatment is employed to further modify the microstructure and the mechanical performance. The WAAMed Al-Zn-Mg-Cu alloys at both as-deposited and heat-treated states exhibit homogeneous microstructure composed of fine equiaxed grains without preferred orientation. T6 heat treatment significantly improves the microhardness and mechanical properties of the as-deposited alloy. The microhardness of the T6 treated alloy reaches 178.3 HV, which is 61% higher than that of the as-deposited sample. The ultimate tensile strength, yield strength, elongation of the T6 treated alloy along horizontal and vertical directions are 469.7(±5.1) MPa, 366.3(±1.4) MPa, 6.4 (±0.4) % and 454.3(±18.8) MPa, 364.7(±16.7) MPa, 5.9 (±0.5)% respectively, demonstrating that the WAAMed nano-treated Al-Zn-Mg-Cu alloy has excellent mechanical isotropy.