Tensile Creep of Alumina‐Silicon Carbide “Nanocomposites”

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Abstract
The tensile creep behavior of an (Al 2 O 3 ‐SiC) nanocomposite that contains 5 vol% of 0.15 μm SiC particles is examined in air under constant‐load conditions. For a stress level of 100 MPa and in the temperature range of 1200°–1300°C, the SiC reduces the creep rate of Al2O3 by 2–3 orders of magnitude. In contrast to Al 2 O 3 , the nanocomposite exhibits no primary or secondary stages, with only tertiary creep being observed. Microstructural examination reveals extensive cavitation that is associated with SiC particles that are located at the Al 2 O 3 grain boundaries. Failure of the nanocomposite occurs via growth of subcritical cracks that are nucleated preferentially at the gauge corners. A modified test procedure enables creep lifetimes to be estimated and compared with creep rupture data. Several possible roles of the SiC particles are considered, including (i) chemical alteration of the Al 2 O 3 grain boundaries, (ii) retarded diffusion along the Al 2 O 3 ‐SiC interface, and (iii) inhibition of the accommodation process (either grain‐boundary sliding or grain‐boundary migration).

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