Abstract
The microscopic aspect of creep-fatigue failure process in a 6061 aluminum alloy composite reinforced with SiC whiskers, SiCw/6061, was studied at high temperature, with specific attention being paid to the interaction between whiskers and the small crack growth. It was shown that the creep-fatigue damage progressed according to the following procedures: (i) the nucleation and the growth of small cracks, or microcracks in the matrix near the interface, (ii) the growth of the small cracks constrained by whiskers, and the increase of the crack density, (iii) the crack face bridging by whiskers, accompanying with the inhibition of the small crack growth by whiskers, (iv) the coalescence of the small cracks, accompanying with the pull-out of whiskers, followed by the final rupture. The crack propagation rates of the SiCw/6061 were also studied, comparing with those of the matrix alloy, on the basis of non-linear fracture mechanics parameter; creep J-integral. An interesting correlation of the creep-fatigue crack growth rates between the SiCw/6061 and the matrix alloy and other kinds of metallic materials was found, by taking account of the creep ductility.
