Effect of multi-pass friction stir processing and rolling on microstructure of interface structure and mechanical properties of 2024Al/AZ31B composites

Al/Mg laminated composites were successfully prepared by multi-pass friction stir processing(M-FSP) and rolling, and the effects of interface structure on their microstructure and properties were studied by Scanning Electron Microscopy (SEM) and Backscattering Diffraction (BSD). The results showed that there were two layers of intermetallic compounds (IMCs) at the interface of the composites after M-FSP, and the average grain size on 2024Al and AZ31B layers decreased from the initial 12.79 μm and 15.06 μm–3.59 μm and 6.36 μm, respectively. For M-FSP + Rolling(F + R) samples, after rolling process, the initially straight IMCs layers were fragmented and embedded on the two matrix layers to increase the interface bonding, while the average grain size on the 2024Al and AZ31B sides were further refined to 2.16 μm and 4.26 μm. The ultimate tensile strength of the F + R sample was increased to 20.6%, with an average value of 322 MPa, compared with the M-FSP samples. This research using M-FSP + Rolling can improve the interface bonding and refine the microstructure, thereby improving the mechanical properties of the composites.