Influence of friction stir processing on microstructure and properties of AA7075/TiB2 in situ composite

Friction stir processing (FSP) is a novel solid state method to homogenize the distribution of particles in aluminum matrix composites (AMCs). AA7075/TiB2 AMCs were prepared by the in situ reaction of inorganic salts K2TiF6 and KBF4 with molten aluminum. The microstructure, before and after FSP, was studied using optical and scanning electron microscopy. TiB2 particles were segregated and clustered at the grain boundaries. The fabricated composite was subjected to single pass FSP using a friction stir welding machine. FSP changed the distribution of TiB2 particles to be intragranular. TiB2 particles fragmented during FSP and were rounded due to the abrading action of the rotating tool. FSP significantly enhanced the mechanical and wear properties of the composite. The details of fracture morphology, worn surface and wear debris are also presented in this paper.