Innovative Crossover Aluminum Alloys for Extreme Space Environments: AMAG CrossAlloy.57

Aluminum alloys are of critical importance for most aerospace and space applications due to their high strength to density ratio. Nevertheless, the development of such technology is significantly hindered by extreme space conditions, including temperature fluctuations, vacuum and high-energy radiation. Consequently, the formation of vacancies and the dissolution of associated precipitates eventually lead to severe degradation of strength, hardness and creep resistance in conventional precipitation-hardened alloys when exposed to these conditions.

To enhance radiation resistance and improve durability, a range of strategies have been investigated. These strategies encompass alloy variations and modifications to the heat treatment process. The T-Mg₃₂(Zn,Al)₄₉ phase is of particular interest, given its notably high number of atoms per unit cell. To promote the formation of T-phase particles, it is necessary to employ a chemistry combination of the 5xxx (Al-Mg) and 7xxx (Al-Zn) series. Preliminary transmission electron microscopy (TEM) analyses confirm the presence of stable T-phase particles in such alloys upon correct heat treatment. Experiments involving ionizing radiation at levels of up to 1 dpa have confirmed a high degree of radiation resistance, as evidenced by the maintenance of microstructural integrity. In contrast to conventional hardening phases like Mg₂Si, the T-phase demonstrated stability, exhibiting minimal morphological changes or void formation, even under high radiation doses.

These findings emphasize the importance of T-phase-hardened alloys for long-duration space missions, where material durability is of the utmost importance. AMAG is currently investing in the industrialization of the crossover concept (CrossAlloy® .57) and conducting extensive characterization of rolled sheets and plates.