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

Abstract

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 Al₃Fe phases. To refine Al₃Fe phases and strengthen Al matrix, we developed an in-situ liquid-solid reaction strategy based on Al–Mg–Fe₂O₃ system to fabricate a MgAl₂O₄ particle-reinforced Al–2Fe composite. Results show that the formation of MgAl₂O₄ particles is primarily governed by the diffusion of Mg, Al, and O elements and the substitution of Mg and Al for Fe in Fe₂O₃. MgAl₂O₄ 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 Al₃Fe crystals by providing coherent interfaces; while only the nanosized MgAl₂O₄ particles acted as nucleation sites of Al crystals. Compared with the Al–2Fe alloy, the sizes of Al grains and Al₃Fe 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 MgAl₂O₄ particles, which refine the Al grains and Al₃Fe phase and strengthen the Al matrix.