Simultaneously improving strength and ductility of laser-powder-bed-fused Al–Zn–Mg–Cu–Ti alloys by controlling phase structure of Al3Ti

Titanium (Ti) addition enabled the laser-powder-bed-fusion (LPBF) fabrication of 7075 (Al–Zn–Mg–Cu) alloys under the heterogeneous nucleation effect of in-situ Al3Ti phase. However, brittle D022 structured Al3Ti easily formed during LPBF, leading to unpleasant tensile properties. In this study, suppression of D022–Al3Ti was explored by adding a small amount of carbon (C) in LPBF Al–Zn–Mg–Cu–Ti alloys. It was found that C addition resulted in 118% improvement in elongation and simultaneous 23% improvement in ultimate tensile strength. The effect of C on the L12 → D022 transformation was studied by aberration-corrected transmission electron microscope and density functional theory.