High-strength additively manufacturable Al-Zr-Er-Ni alloys with high as-built ductility and thermal stability

Additively manufactured (AM) aluminum (Al) alloys with high as-built ductility offer sustainability, enhanced load-bearing performance, and resistance to residual-stress-induced failure. However, most commercial AM Al alloys have very limited ductility. In this study, we designed an AM Al-1.63Zr-2.38Er-1.34Ni (wt. %) alloy with 16% as-built ductility, while not introducing nanopowders or expensive scandium (Sc) to the formulation. We revealed that Al3Zr accounted for 65% of cavitation in the as-built condition by SEM characterizations. With calculation of phase diagram (CALPHAD)-based integrated computational materials engineering (ICME) simulations, we found that at each Er composition, Zr must not exceed the threshold required to act as a reservoir for the L12 phase transformation (needed for high strength) during aging. An optimized composition was identified following the guideline of Zr = 1.07 × Er; this composition enhances the ductility from 0.9% to 16% (1600% increase) in the as-built sample, while only decreasing strength by 27% compared to the benchmark alloy. The strength is preserved even after aging for 48 hours at 400°C.