Dry sliding wear behavior of sinter forged micrometric and nanometric yttrium oxide reinforced AA-7075 matrix composites

This study aims to investigate the dry sliding wear behaviour of AA-7075 based metal matrix composites developed by powder metallurgy route. AA-7075 metal matrix composites have been developed with 1–15 vol% micrometric yttrium oxide particulate reinforcement and 0.1–3 vol% nanometric yttrium oxide particulate reinforcement by sinter forging.The matrix and reinforcing powders were blended together to obtain a homogeneous composite powder mixture which was cold compacted and further sintered under pure nitrogen atmosphere. The sintered compacts were forged in a closed die to attain full density. The hot forged samples were further artificially age hardened to peak hardness. Wear behavior of AA-7075 and its composites at peak aged condition were investigated at various loads and sliding speeds. The coefficient of friction and wear rate were determined with respect to different volume fractions of micrometric and nanometric yttrium oxide additions to AA-7075 alloy matrix. The overall wear at a constant volume fraction was found to be lower for the compositions having nanometric Y₂O₃ as compared to micrometric Y₂O₃. Further the basic wear mechanism of pure aluminum 7075 alloy and reinforced composites consisted of adhesive wear with plastic deformation followed by abrasive wear (due to hard reinforcement particles).Material strengthening by precipitation hardening and reinforcement addition and the role of the forging operation and yttria reinforcements in the removal and uniform distribution of oxide layers present on the AA-7075 powder particles were accountable for the improvement in the wear resistance of the composites.