Influence of direct aging treatment on microstructure and mechanical properties of Al-4Cu-2Mg-0.3Sc-0.7Zr alloy processed by selective laser melting

This work investigates the microstructure and mechanical properties of select laser melting (SLM) fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloys after direct aging treatment. In the as-fabricated alloy, typical duplex grain microstructure, primary Al3(Sc, Zr) precipitates and CuMg co-segregation are observed. After aging treatment at 203 °C for 2.5 h, it was found that two types of S (Al2CuMg) precipitates with {100}Al and {120}Al growth direction. The superlattice lattice confirmed the presence of the secondary Al3(Sc, Zr) precipitates with L12 structure after aging at 225 °C to 496 °C. The disappearance of CuMg segregation and the coarser scale Al3(Sc, Zr) particles lead to the poor Zener-pinning effect and abnormal growth of fine grains at 496 °C aged. The fine secondary Al3(Sc, Zr) precipitates enhanced mechanical properties greatly, the yield strength achieved 435.5 MPa (increased about 18 %) with the elongation of 10.5 % after aging at 440 °C. •The precipitation behavior of SLM fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloy during aging process was investigated.•The two types of S (Al2CuMg) particles and the Al3(Sc, Zr) particles were characterized, respectively.•The relationship between microstructure and mechanical properties was investigated.