Influence of boron nitride nanoparticles on microstructure and wear behavior of AA6082/TiB₂ hybrid aluminum composites synthesized by friction stir processing

Friction stir processing (FSP) was successfully applied to synthesize AA6082/(TiB₂ + BN) hybrid aluminum matrix composites (AMCs) and compared with AA6082, AA6082/TiB₂ AMC and AA6082/BN AMC. TiB₂ and BN particles were compacted into a groove and FSP was carried out at optimized parameters. The microstructure was investigated by optical, scanning electron and transmission electron microscopy. Sliding wear behavior was evaluated using a pin-on-disc apparatus. Micrographs revealed a homogenous dispersion of particles in the aluminum matrix irrespective of the region within the stir zone. There was no segregation of two type particles in the hybrid AMC. Effective interfacial bonding between the particles and the aluminum matrix was demonstrated with extensive grain refinement occurring in the matrix. The shape and morphology of the TiB₂ particles altered during FSP while the BN particles were intact. The addition of BN nanoparticles enhanced the wear resistance of AA6082/TiB₂ AMC by acting as a solid lubricant and forming a tribo film. The wear mode changed with the addition of TiB₂ and BN as dispersed particles. BN particles reduced the iron content in the wear debris of AA6082/TiB₂ AMC which is beneficial for a reduction in counterface wear.