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.