Sliding wear response of ultrasonic-assisted stir-squeeze cast Al-Zn(-Mg) alloy/ZrO 2p composite: wear mechanism and subsurface deformation

Abstract The character of hard ZrO 2p in dry sliding wear of Al-Zn(-Mg) alloy was investigated in the cast and heat-treated conditions using a pin-on-disc wear tester at fixed sliding speed (3.5 m s −1 ) and varying applied pressure (0.5–2.125 MPa), giving special accentuation on the response parameters such as seizure resistance, wear rate, and bulk temperature rise. Hardness behavior was also studied for the same concerning materials in accordance with ASTM standards. The composites exhibited enhanced hardness, wear and seizure resistance, and greater temperature rise over the alloy. Indeed, the wear rate at preliminary stages increased with increasing applied pressure up to a transition limit beyond which it upsurged abruptly to greater value at the seizure pressure. Heat treatment also significantly improved the hardness, and resistance to wear and seizure. Amongst, heat-treated composite embedded with 4% ZrO 2p yielded the highest hardness of 180 HV and seizure pressure of 2.125 MPa, respectively. The deformation in the subsurface was examined in terms of microhardness variation along the depth perpendicular to the worn surface. It was detected that the presence of ZrO 2p not only enhanced the seizure resistance but also effectively hampered the extent of subsurface deformation at the seizure. The wear mechanism was prevalently governed through the establishment of the mechanically mixed layer (MML), oxide layer, cracking, and deformed subsurface.