Effects of different additives on microstructure and properties of Al–Zn–Mg–Cu alloys prepared by laser-directed energy deposition

There are always microcracks and pores during the laser additive manufacturing of 7xxx aluminum alloy, which significantly limits its performance improvement and application. This work uses additives to suppress defects and improve the alloy's properties. Here three alloys were prepared by the addition of silicon, TiN, or both. Their microstructure and mechanical properties were investigated in detail. The results show that silicon can inhibit the crack generation by reducing the solidification rate. The grain size is large. TiN can refine the grain and it creates pores. The addition of both can restrain the defects, refine the grains and obtain good comprehensive properties. Moreover, the hardness and wear resistance of A3 are slightly lower than A2 due to the brittle phase generated by the addition of Si. The yield strength, tensile strength, elongation, hardness and wear rate of A3 alloy treated by T6 are 214.8 ​MPa, 262.8 ​MPa, 2.59 ​%, 130.9 HV and 2.24 ​× ​10⁻³ mm³/(N·m).