Metallurgical reaction and joining phenomena in friction welded Al/Fe joints

The continuous drive friction welding of aluminum alloy to stainless steel was investigated in this paper. Microstructural characterization, intermetallic compound (IMC), and mechanical properties of the friction welded Al/Fe joint were studied. Results showed that thermal mechanically affected zone (TMAZ) at the Al side was subjected to both thermal cycling and mechanical force, and grain size was 1–3 μm, and streamlines were more dramatically than at the steel side. In fully dynamic recrystallized 127 zone (FDRZ), microstructure became the fine equiaxed grains, and its width at the steel side was about 5 μm. The local Si enrichment IMC layer was formed at the interface area of Al/Fe joint, and its average thickness was about 300 nm. IMC layer was relatively flat at the steel side, while uneven at the Al side. The hardness reached to the maximum value (395.8 HV) at the steel side in FDRZ, and the average hardness was only 76 HV in heat-affected zone (HAZ) at the Al side. When forge pressure was below 220 MPa, the tensile strength of joint was approximately linearly related to the forge pressure.