Laser powder bed fusion of Zr-modified Al-Cu-Mg alloy: Processability and elevated-temperature mechanical properties

Abstract

• Hot-cracking was affected by the volume fraction and size of the equiaxed grains. • The nucleation potency of L1 2 -Al 3 Zr phase was evaluated based on the E2EM model. • Both as-fabricated and T6-treated samples exhibited excellent YS from 150 °C to 350 °C. Zr modification is an effective method for improving hot-cracking resistance and elevated-temperature mechanical properties during laser powder bed fusion (L-PBF) of traditional medium and high strength wrought aluminum alloys. This study investigated the L-PBF processability and elevated-temperature mechanical properties of a Zr-modified 2024Al alloy. It was found that the hot-cracking susceptibility increased with the increased scanning speed, which was in reasonable agreement with the modified Rappaz–Drezet–Gremaud criterion. Furthermore, the primary L1 2 -Al 3 Zr precipitates, which acted as efficient nucleation sites, precipitated at the fusion boundary of the melt pool, leading to the formation of a heterogeneous grain structure. The yield strength (YS) of the as-fabricated samples at 150, 250, and 350 °C was 363, 210, and 48 MPa, respectively. Despite the slight decrease to 360 MPa of the YS when tested at 150 °C, owing to the additional precipitate strengthening from the L1 2 -Al 3 Zr precipitates, the YS achieved yield strengths of 253 and 69 MPa, an increase of 20.5% and 30.4%, when tested at 250 and 350 °C, respectively. The yield strengths in both the as-fabricated and T6-treated conditions tested at 150 and 250 °C were comparable to those of casting Al-Cu-Mg-Ag alloys and superior to those of traditionally heat-resistant 2219-T6 and 2618-T6 of Al-Cu alloys.