Effect of Strengthening Particles on Microstructure and Tribological Properties of Aluminum Based Nano-composites

In this research surface composite layers containing nano sized TiB2, Al2O3-TiB2, ZrO2 and CNTs particles have been fabricated on Al alloy substrate by friction stir processing. Effect of different processing variables such as number of passes and strengthening particle on distribution of particles, hardness and tribological properties of surface nanocomposite layer have been evaluated by electron microscopy, hardness and wear test. Results showed that surface properties of aluminum alloy will be enhanced and the optimum conditions of properties which can be determined by comparing the effects of different parameters will be obtained. An increase in the number of passes up to four modifies microstructure and accordingly mechanical and tribological properties were enhanced. Maximum hardness of 210 HV was measured for specimens FSPed with Al2O3-TiB2 powder after four passes. Surface composite produced by FSP significantly improved the dry sliding wear resistance of the Al6061 alloy by changing the wear mechanism. The FSPed sample with Al2O3-TiB2 particles had higher wear resistance in comparison with others. This enhancement is a consequent of better bonding between particles and aluminum matrix and higher microhardness.