Prediction of tensile power law creep constants from compression and bend data for ZrB2–20 vol% SiC composites at 1800 °C

Here we consider our four-point flexure and compression creep results obtained under Ar protection at 1800 °C to predict the tensile creep behavior of a ZrB2–20 vol% SiC ultra-high temperature ceramic. Assuming power law creep, and based on four-point bend data, we estimated the uniaxial creep parameters using an analytical method present in the literature. Both predicted and experimental compressive stress exponents were found to be in excellent agreement, 1.85 and 1.76 respectively, while observation of the microstructure suggested a combination of diffusion and grain boundary sliding creep mechanisms in compression. Along with the microstructural evidence associated with the tensile regions of the flexure specimens, the predicted tensile stress exponent of 2.61 exceeds the measured flexural value of 2.2. We assert an increasing role of cavitation to the creep strain in pure tension. This cavitation component adds to the dominant grain boundary sliding mechanism as described below and elsewhere for flexural creep.