Creep behavior of a zirconium diboride–silicon carbide composite

Abstract

Abstract Flexural creep studies of ZrB 2 –20 vol% SiC ultra-high temperature ceramic were conducted over the range of 1400–1820 °C in an argon shielded testing apparatus. A two decade increase in creep rate, between 1500 and 1600 °C, suggests a clear transition between two distinct creep mechanisms. Low temperature deformation (1400–1500 °C) is dominated by ZrB 2 grain or ZrB 2 –SiC interphase boundary and ZrB 2 lattice diffusion having an activation energy of 364 ± 93 kJ/mol and a stress exponent of unity. At high temperatures (>1600 °C) the rate-controlling processes include ZrB 2 –ZrB 2 and/or ZrB 2 –SiC boundary sliding with an activation energy of 639 ± 1 kJ/mol and stress exponents of 1.7 n n = 2.2. Microstructure observations show cavitation may partially accommodate grain boundary sliding, but of most significance, we find evidence of approximately 5% contribution to the accumulated creep strain.