Microcosmic mechanism of performance enhancement of wire arc additive manufactured Al-Zn-Mg-Cu alloy based on heat treatment

Al-Zn-Mg-Cu alloys are widely used in aerospace structures because of their excellent performances. To improve the poor mechanical performance of the Al-Zn-Mg-Cu arc additive manufactured deposit, heat treatments were used for the enhancement of mechanical performances. The microstructure of the deposits was improved after heat treatment due to the decomposition of intermetallic compounds. Meanwhile, the solid solution of alloying elements and the phase transformation led to two strengthening mechanisms: solid solution strengthening and the precipitation strengthening. The performance enhancement of the deposits was most significant under the T6 heat treatment. The horizontal and vertical strength increased to 513 and 504 MPa, respectively, and the hardness increased to 205 HV with more uniformly distribution in the vertical direction.