Effects of rare earth modification on microstructure refinement and mechanical properties of Al-2 wt%Fe alloys

The microstructure and mechanical properties of Al-2 wt%Fe alloys after mixed RE modification, homogeneous annealing and cold rolling have been studied using OM, XRD, SEM and mechanical testing. Results showed that during traditional casting, the α -Al grain and Al 3 Fe/Al 6 Fe intermetallic could be effectively refined by the mixed RE in Al-2 wt%Fe alloy. The average grain size of primary α -Al with 0.5 wt% RE addition is half smaller than that without RE. The addition of mixed RE makes the mechanical properties of alloys initially increased and then decreased. The RE elements that enriched in front of the solid/liquid interface formed Al 8 Fe 2 Ce at grain boundaries of α -Al. An addition of 0.7 wt% mixed RE lead to the preferential formation of the granular Al 11 Ce 3 , which the La were dissolved in. However, the formation of Al 11 Ce 3 weakened the refining effect of mixed RE on the microstructure, also deteriorated the mechanical properties of the alloy. Homogeneous annealing decomposes lamellar Al-Fe phase into short rods, and cold rolling process makes the second phase dispersively and uniformly distributed in the primary α -Al matrix. The elongation and tensile strength of alloy with 0.5 wt% mixed RE addition are increased by 50.14% and 10.67% respectively compared with those of unmodified alloy in cold rolled state.