Creep Cavitation Behavior in Polycrystalline Ceramics

Small-angle neutron scattering measurements have been performed on compression-crept alumina characterized by a relatively thick, continuous, grain boundary phase, another alumina with essentially no continuous grain boundary phase, and a silicon carbide with a relatively thin, continuous, grain boundary phase. The neutron scattering measurements, which provide a means of characterizing nucleation rates, growth rates, and morphologies of typical grain boundary cavities during the early stages of creep, have shown unequivocally that cavity nucleation does in general occur. They also have identified very significant differences in the relative roles of cavity nucleation and growth in these three ceramic systems. Measured cavitation parameters are outlined and discussed in relation to micro-structural differences and appropriate cavitation models.