Influence of aging, varying particle size and volume fraction of Al₂O₃ particles on the hardness and wear behavior of Al 7150 alloy composite produced by hot uniaxial compaction method

The influence of aging, particle size and volume fraction (5, 10, 20 and 25%) of alumina particulates on the hardness and wear behavior of Al 7150 alloy composites produced by hot uniaxial compaction method was investigated. The as-received Al₂O₃ particulates were first mechanically ball milled for durations of 45, 180, 360, 420 and 580 min to reduce its particle size. The milled alumina particles of 165 nm, 65 nm, 45 nm, 27 nm and 21 nm were later independently blended with the Al 7150 alloy powders to produce five sets of cylindrical specimens using a punch-die setup. The compaction pressure was 500 MPa with a holding time of 3 h, at a temperature of 400 °C. The Vickers microhardness tests revealed an improvement in the hardness with the increase in the volume % of the reinforcement and decreasing particulate size. The Age hardenability of the composites was also investigated by first solutionizing the composite samples followed by aging at 3 h (T4-underage), 24 h (T6-peak age) and 96 h (T7-overage). The wear behavior of the samples was studied by comparing the wear rate of the un-reinforced alloy and non-heat treated (reinforced) Al 7150 alloy composite samples with T6 heat treated composite specimens using a pin on disc wear testing machine under different load and sliding distance conditions. The test specimens were characterized using XRD, FESEM and EDS analysis. Apart from the effect of particle size and volume fraction of Al₂O₃ reinforcement, the precipitation hardening which occurred during aging, influenced the microhardness and wear behavior of the composite samples. (paper)