A novel approach for producing in situ Al-Al2Cu composite via friction stir processing

In situ Al-Al2Cu surface composites were synthesized via friction stir processing (FSP) at aluminium plate with brass foil interlayer(s). The effects of rotational speed, number of FSP passes, and number of brass interlayers were investigated. Defect-free surface composites with the Al2Cu particles were successfully produced in all the processed FSP conditions. The surface composites consisted of a fine grained aluminium matrix (2-10 mu m), Al2Cu particles and some unreacted brass fragments remain mainly at the bottom of the stir zone. An improvement in hardness (up to 300%) compared with the aluminum base metal was achieved. Also, the activation energy and diffusion pre-factor of Al2Cu phase produced by FSP were estimated.