Iron Aluminide-Reinforced Aluminum Matrix Composite Produced by Multi-Pass Friction Stir Processing

The structural evolution and mechanical properties of an Al–Mg alloy were studied after multi-pass friction stir treatment (FST) with the addition of 5, 10, and 15 vol % iron powder. With an increasing number of FST passes, iron-containing particles are refined and more uniformly distributed within the aluminum matrix. Diffusion interactions between Al and Fe during FST lead to the formation of intermetallic compounds of the Al6Fe and Al13Fe4 types. The in-situ diffusion reaction between Al and Fe is not complete even after four FST passes, since iron particles encased in Al-Fe intermetallic compounds are still present in the mixing zone. After four-pass FST, a uniform distribution of intermetallic compounds of the Al6Fe and Al13Fe4 types was achieved in the mixing zones, which doubled the microhardness compared to the base alloy. The tensile strength of the composites also increases while reducing ductility.