Assessment of microfracture mechanisms in Al_2O_3/6061Al and SiC/6061 Al discontinuous reinforced composites

摘要

Microfracfture mechanisms are investigated in artificially aged discontinuously reinforced metal matrix composites (MMCs). Fracture behavior is presented for a 6061 Al alloy reinforced with Al_2O_3 and SiC particulates. Stir-cast processing was used to fabricate both Al_2O_3/6061 Al and SiC/6061 Al MMCs. Emphasis is placed on the role played by the particulate/matrix interface in these materials as the interfacial character and integrity influence microfracture mechanisms. Interface and near-interface phase characterization was conducted using electrochemical dissolution, and optical, scanning, and transmission microscopy. Crack initiation and crack propagation behavior was investigated in the under aged, peak-aged, and over-aged conditions using double notched, 4-pt. bend specimens and half-inch short bar specimens, respectively. The effect of aging, associated microstructure development, and reinforcement type on microcrack initiation and crack propagation mechanisme is discussed.