Investigation of through-thickness microstructural evolution and mechanical properties variation in friction stir alloyed Al-Fe alloy system

The present study investigates the through-thickness microstructural evolution, particle dispersion, and mechanical properties of the Al-Fe alloy system fabricated via friction stir alloying (FSA). The EDS and TEM analysis confirm Al 13 Fe 4 as the main reaction product of the Al-Fe alloy system in the present study. However, the inhomogeneity in the distribution of Fe and Al 13 Fe 4 IMC particles was observed across the thickness of the fabricated alloy. The middle section (starts at 2 mm and ends at 4 mm from the FSA surface) of the alloy was identified as the best region in terms of particle dispersion, fine grain size (~3.6 µm), and improved mechanical properties. The average microhardness in the stir zone (SZ) of the middle region was increased by ~62% as compared to the base metal (BM). The middle section also shows the maximum ultimate tensile strength (UTS) of ~134 MPa which is ~30% and ~38% higher than the UTS of the top and bottom sections, respectively. A detailed discussion is provided on the correlation of mechanical properties with various factors such as Fe particle dispersion, material flow, IMC morphology, and involved reaction mechanisms.