High temperature rupture of an SiC particulate reinforced Al composite under multiaxial stress states

Specimens of an SiC particulate reinforced Al alloy (10 vol.% SiCp-2124 Al) were tested at 678 K to failure under three different stress states: uniaxial tension using smooth bar specimens, biaxial shear using a novel double shear specimen geometry, and triaxial tension using notched bar specimens. Rupture times are compared for the three stress states with respect to the von Mises effective stress, the maximum principal stress, and the principal facet stress. The validity of these parameters is judged according to how well the rupture time of the biaxial and triaxial stress states can be predicted using the rupture data for specimens under uniaxial tension. The results indicate that the high temperature rupture process is dominated by cavity nucleation at the particle/matrix interface and cavity growth by dislocation creep. Microstructural observations of microcracks associated with cavity coalescence are shown to be consistent with this finding.