Externally-Physical-Field-Assisted Aging Precipitation in Aerospace Aluminum Alloys: A Review

Externally physical fields such as stress field, electric field and magnetic field have been demonstrated influence the equilibria and kinetics of solid-state transformations in metals and alloys. This review focuses on the effects of externally physical fields on the aging precipitation of aerospace Al alloys including 2xxx Al-Cu alloys, 7xxx Al-Zn-Mg alloys as well as the advanced Al-Li alloys. While the η' phase in Al-Zn-Mg alloy and the T1 phase in Al-Li alloy showed no obvious stress-orientating effect, the precipitation of θ' phase in Al-Cu alloy showed obvious stress-orientating effect depending on the applied stress direction. Regarding precipitation kinetics, aging under stress field, electric field and magnetic field all can enhance the aging precipitation of aerospace Al alloys. The understanding of the effects of externally physical field on the aging precipitation in Al alloys is very preliminary. It appears that while the stress field acts on the thermally activated transformation, the athermal effect associating with electromigration of electromagnetic field has been considered responsible for the enhanced aging precipitation.