FRACTURE CHARACTERISTICS OF AN AL-SI-MG MODEL COMPOSITE SYSTEM

The fracture toughness characteristics of an Al-Si-Mg model composite system were examined. Through manipulating composition and processing variables, controlled variations in particle volume fraction and matri x flow properties were produced and tested using J(IC) tests. Metallog raphic analysis shows that the fracture process proceeds by the cracki ng of Si particles ahead of the crack tip in a very localized region. This is compared with results from smooth uniaxial tensile specimens w hich, while exhibiting the same particle cracking mode of fracture, ha ve damage distributed over a wider area of the specimen. The results f or the Al-Si-Mg model alloys are compared with J(IC) results for comme rcial composite systems, and the differences observed are discussed in terms of the characteristics of the reinforcement particles.