Damage mechanisms in a cast ductile iron and a Al2O3p/Al composite

Mechanical behavior and damage mechanisms of an Al2O3 particulate-reinforced Al matrix composite (Al2O3/Al) prepared by pressure infiltration are investigated and compared with those of a cast ductile iron. In addition to low cost and reduced weight, the composite has a Young's modulus comparable to the ductile iron. However, its fracture toughness is lower than that of the ductile iron. Interface debonding between the graphite and ferrite is responsible for the crack initiation behavior of the ductile iron. The crack in the ductile iron is arrested by the ductile ferrite phase surrounding the graphite, leading to high fracture toughness. For the Al2O3p/Al composite, the dominating crack initiation mode is particulate cracking. Interface debonding and zigzag cracking of particulates are additional fracture modes. The high content of Al2O3 particulates and the high thermal and elastic incompatibilities between the Al matrix and Al2O3 particulates result in brittle fracture and low fracture toughness for the composite. Possible ways to increase the fracture toughness of the Al2O3p/Al composite material are also outlined.