Computational design of a crack-free aluminum alloy for additive manufacturing

The design of new alloys adapted to LPBF and combining suitable mechanical strength together with a low cracking susceptibility is a promising way to produce defect-free parts made of aluminum. The current work proposes a design procedure relying on the decrease of the brittle temperature range to mitigate the hot cracking issue and additional optimization criteria concerning the phases fractions and the solid solution strengthening to preserve the mechanical strength and some ductility. The optimization functions are included in an aggregated genetic algorithm for a rapid and efficient identification of the optimal composition. The algorithm determined a promising alloy, with a brittle temperature range of only 9 °C, and mostly constituted of FCC phase (around 90%), with some Mg₂Si and Al₉FeNi precipitates. The alloy is found suitable for the LPBF process with no cracks observed. Hence, the criterion for the mitigation of hot cracking is validated. Mechanical results shown a high yield stress and ultimate trensile stress but an elongation at break quite low compared to conventional manufactured aluminum alloys.