Tribological Behavior of Copper Chilled Aluminum Alloy (LM-13) Reinforced with Beryl Metal Matrix Composites

The present investigation aims at developing copper chilled aluminum alloy (LM-13) reinforced with beryl using stir casting method. Matrix alloy was melted in a composite making furnace to a temperature of about 700°C to which preheated reinforcement particles was added (3 wt.% to 12 wt.% in steps of 3 wt.%), stirred well and finally poured in to an AFS standard mold containing copper end chills of different thickness (10, 15, 20 and 25 mm) placed judiciously for directional solidification. The resulting chilled composites were subjected to microstructural, XRD, mechanical properties (strength and hardness) and tribological behavior.Results of the microstructural and XRD analysis indicate that the chilled castings were sound with good distribution and presence of all the particles. The bonding between beryl reinforcement and Al alloy matrix (LM-13) leads to excellent isotropic properties without any shrinkage or microporosity. Mechanical characterization indicates that both strength and hardness were maximum in the case of copper chilled MMC containing 9 wt.% and 12 wt.% reinforcement respectively. Strength and hardness of chilled MMC are found to increase by 9.88% and 16.66% as compared against the matrix alloy. It is observed that because of the ceramic (beryl) reinforcement in aluminum alloy, the wear resistance of the chilled composite developed has increased with increase in reinforcement content. At lower load, chilled MMCs exhibited mild wear regime with high coefficient of friction and at higher loads they exhibited severe wear with better wear resistance compared to un-chilled composite. It is observed that the increase in mechanical properties and wear resistance are due to incorporation of beryl reinforcement, the effect of chilling that has resulted in grain refined microstructure with good bonding of the matrix and the reinforcement.