Fractography of cryogenic chill casted ASTM A 494 M grade nickel alloy metal matrix composites

ASTM A 494 M grade Ni-Garnet composites containing four different weight percentages 3%, 6%, 9% and 12% of Garnet samples have been fabricated by using cryogenically cooled copper chill stir casting method. Effects of volume percent of Garnet particles on tensile strength, and fracture surfaces of Nickel Garnet composites have been investigated. The highest tensile strength was achieved in the specimen containing 9 Wt. % garnet produced with 25 mm chill thickness which shows an increase of 14% in comparison to the no chill cast reinforced alloy. Microscopic investigations of fracture surfaces revealed that fracture in a brittle manner with little or no necking happening. By increasing garnet content and chill thickness, the composites fracture goes in a more severely brittle manner. The fracture behavior of the composites was altered significantly by the presence of garnet particles and the crack propagation through the matrix and the reinforcing particle clusters resulted in the final fracture.