Compressive creep of fine and coarse-grained T3SiC2 in air in the 1100-1300°C temperature range

Herein, we report on the compressive creep behavior of hot isostatically pressed (HIPed) fine-grained (FG) and coarse-grained (CG) Ti3SiC2 in the 1100-1300 degrees C temperature range. The creep behavior is characterized by three regimes, a primary, quasi-steady state and a tertiary. At lower stresses, the creep rates of the two microstructures are comparable suggesting that dislocation creep is operative. At approximate to 2, the stress exponents in the quasi-steady state regime are comparable to those measured in tension; the creep rates in compression, however, are roughly an order of magnitude lower. At relatively high stresses and/or temperatures, the stress exponents of the FG samples increase dramatically and the creep rates of the CG samples are higher than their FG counterparts. Both observations suggest a change of mechanism from dislocation creep to possibly sub-critical crack growth, in which delaminations play an important role. This conclusion is bolstered by post-deformation microstructural analysis that shows evidence for sub-critical crack growth. The minimum creep rates of pressureless sintered Ti3SiC2 samples were roughly an order of magnitude higher than HIPed samples, with comparable grain size strongly suggesting that some form of grain boundary related deformation, such as decohesion and/or sliding, is playing an important role in the sintered samples. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.