Unprecedently radiation-tolerant Al alloys via vacancy-mediated anomalous solid-state phase transformation

Vacancies play a critical role in diffusion-dominated solid-state phase transformations of materials. A classical paradigm of physical metallurgy is that quenched-in excess vacancies are tuned to regulate the precipitation hardening in lightweight aluminum alloys. Here we demonstrate that a vacancy-alloying effect, whereby a high concentration of vacancies induced by in-situ TEM heating or ion irradiation, completely overturns the traditional precipitation sequence in Al-Cu alloys microalloyed with Sc. An anomalous phase transformation appears via a spinodal decomposition process with L 1₀-Al₂Cu₂ phase as the product nanoprecipitate and the traditional precipitation sequence turning GP zones into θ′′ and θ′ precipitates is reversed. The vacancy-triggered spinodal decomposition is capable of absorbing and stabilizing vacancies continually, enabling the minor Sc-added Al-Cu alloys to reach an unprecedented resistance to void swelling or ductility degradation, even irradiated to 100 dpa. We envisage that the anomalous vacancy-accommodating phase transformation may pave a way for the development of advanced radiation-resistant metallic alloys with promising applications in nuclear industry and space missions.