Tensile creep of fine grained (3-5 μm) Ti3SiC2 in the 1000-1200°C temperature range

In this paper we report on the tensile creep behavior of fine-grained (3-5 mum) Ti3SiC2 in the 1000-1200 degreesC temperature, T, range and the 10-100 MPa stress, sigma, range. The creep behavior is characterized by three regimes a primary, quasi-steady state and a tertiary. In the quasi-steady state range and over the entire range of testing temperatures and stresses, the minimum creep rate, (epsilon) over dot(min) is given by: (epsilon) over dot(min)(s(-1)) = (epsilon) over dot(0).exp[19 +/-1].(sigma/sigma (0))(1.5 +/-0.1).exp[(-445 +/- 10) kJ/mol / RT] where sigma (0) = MPa and (epsilon) over dot(0) = 1 s(-1). The times to failure, t(f), were fitted to an expression of the form: t(f)(s) = t(0).exp[-2 +/-1].[(epsilon) over dot(min)/(epsilon) over dot(0)](-0.9 +/-0.1) where t(0) = 1 s. Interrupted creep tests show that volume-conserving plastic deformation is the dominant source of strain during the secondary creep regime, while cavities and microcracks are responsible for the acceleration of the creep rate during the tertiary creep regime. Like in ice, large internal stresses, especially at high stresses, are developed in Ti3SiC2 during deformation, as a consequence of its extreme plastic anisotropy. The response of Ti3SiC2 to stress appears to be determined by a competition between the rates of accumulation and relaxation of these internal stresses. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.