Formation of Cu2FeAl7 phase in friction-stir-welded SiCp/Al–Cu–Mg composite

Extruded 15 vol.% SiCp/Al–Cu–Mg composite was friction-stir-welded (FSW) and subjected to subsequent post-weld T4-treatment. The formation of Cu 2 FeAl 7 phase with Fe resulting from steel tool wear was identified at or near the SiC particle interfaces by using transmission electron microscopy, high-resolution electron microscopy and differential scanning calorimetry. Two types of Cu 2 FeAl 7 phases were observed: a single crystal phase and a polycrystalline nanostructured phase. No elemental iron was detected. The formation mechanism of the Cu 2 FeAl 7 phase is discussed.