Additive manufacturing of isotropic-grained, high-strength and high-ductility copper alloys

This work reports additive manufacturing of nickel-aluminum-bronze alloys by electron beam powder bed fusion (EB-PBF), with a relatively homogeneous microstructure at the micro- to meso-scale and exhibiting an exceptional combination of tensile strength and ductility — well surpassing that of conventionally wrought counterparts. The attainment of both high yield and ultimate tensile strength are attributed to collective effects of uniformly distributed precipitates, near-equi-axed grains, and a high fraction of high-angle grain boundaries. High tensile ductility originates from a sustainable work-hardening ability via dislocation-dislocation and dislocation-precipitate interactions, enhanced by moderate twinning, stacking faults, and back-stress hardening. Significantly, the EB-PBF alloys exhibit near-isotropic tensile properties in directions parallel and vertical to the build direction due to high-density precipitates enabled by equi-axed grains.