Improvement of microstructure and mechanical property of Al–2Fe alloy though an in-situ reaction of Fe2O3 powder in Al–Mg melts

Al–Fe based alloys exhibit excellent high heat-resistance property but suffer from low strength and hardness because the soft aluminum matrix is interrupted by coarse needle/flake-like Al 3 Fe phases. To refine Al 3 Fe phases and strengthen Al matrix, we developed an in-situ liquid-solid reaction strategy based on Al-Mg-Fe 2 O 3 system to fabricate a MgAl 2 O 4 particle-reinforced Al–2Fe composite. Results show that the formation of MgAl 2 O 4 particles is primarily governed by the diffusion of Mg, Al, and O elements and the substitution of Mg and Al for Fe in Fe 2 O 3 . MgAl 2 O 4 particles with nano and submicron sizes are uniformly dispersed in Al matrix. Those in-situ formed nano and submicron particles serve as heterogeneous nucleation sites of Al 3 Fe crystals by providing coherent interfaces; while only the nanosized MgAl 2 O 4 particles acted as nucleation sites of Al crystals. Compared with the Al–2Fe alloy, the sizes of Al grains and Al 3 Fe phases in composite were reduced by 54.7% and 34.5%, respectively, accompanied by increases of 36.9%, 47.7%, and 40.5% in yield strength, ultimate tensile strength, and Vickers hardness. Furthermore, the elongation was slightly decreased from 16.5% to 13.0%. The improvement of mechanical properties are attributed to the in-situ-formed MgAl 2 O 4 particles, which refine the Al grains and Al 3 Fe phase and strengthen the Al matrix.