Mechanistic understanding on the evolution of nanosized Al3Fe phase in Al–Fe alloy during heat treatment and its effect on mechanical properties

Abstract Al–1Fe (wt%) alloy containing nanosized Al 3 Fe phase was processed by continuous rheo-extrusion, and subjected to heat treatment at different temperatures. During heat treatment, due to the diffusion of Fe atoms, the nanosized Al 3 Fe phase was blunted and fragmented along the width direction, and the bluntness and fragmentation resulted in the spheroidization of Al 3 Fe phase. However, with the extension of heat treatment time, the spheroidized Al 3 Fe phase became coarse and grew along a particular plane. Then, the morphology of Al 3 Fe phase transformed into small plate-like. While, the plate-like Al 3 Fe phase with an average length of 30 µm in the as-cast Al–1Fe (wt%) alloy indicated good thermal stability during heat treatment. The different thermal stability of Al 3 Fe phases was attributed to their size. The large surface curvature of nanosized Al 3 Fe phase significantly accelerated the diffusion of Fe atoms. When the heat treatment temperature was 200 ℃ and 300 ℃, the tensile strength and elongation of the rheo-extruded Al–Fe alloy marginally decreased. The decrease of tensile strength and the decrease of elongation increased when the heat treatment temperature was greater than 400 ℃. The tensile strength and elongation of as-cast Al–1Fe (wt%) alloy were insignificantly altered. Though the loss of tensile strength of Al–Fe alloy containing nanosized Al 3 Fe phase was much greater, its tensile strength was always higher than the tensile strength of the as-cast Al–Fe alloy in the entire heat treatment.