Acta mater. 49 (2001) 4103–4112 www.elsevier.com/locate/actamat TENSILE CREEP OF FINE GRAINED (3–5 μm) Ti 3 SiC 2 IN THE 1000–1200°C TEMPERATURE RANGE M. RADOVIC 1 , M. W. BARSOUM 1 †, T. EL-RAGHY 1 and S. WIEDERHORN 2 1 Department of Materials Engineering, Drexel University, Philadelphia, PA 19104, USA and 2 National Institute of Standards and Technology, Gaithersburg, MD 20899, USA ( Received 23 June 2000; received in revised form 15 June 2001; accepted 15 June 2001 ) Abstract—In this paper we report on the tensile creep behavior of fine-grained (3–5 μm) Ti 3 SiC 2 in the 1000–1200°C temperature, T, range and the 10–100 MPa stress, s, 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, e ˙ min , is given by: e ˙ min (s -1 ) = e ˙ 0 ·exp[19±1]·(s/s 0 ) 1.5±0.1 ·exp  (-445±10) kJ/mol RT  where s 0 = MPa and e ˙ 0 = 1s -1 . The times to failure, t f , were fitted to an expression of the form: t f (s) = t 0 ·exp[-2±1]·[e ˙ min /e ˙ 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 Ti 3 SiC 2 during deformation, as a consequence of its extreme plastic ani- sotropy. The response of Ti 3 SiC 2 to stress appears to be determined by a competition between the rates of accumulation and relaxation of these internal stresses.  2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. Keywords: Creep; High temperature; Oxidation 1. INTRODUCTION By now it is well established that the ternary carbide, Ti 3 SiC 2 , exhibits an unusual combination of proper- ties [1–12] such as high specific stiffness [9] with ease of machinability [3]; good thermal and electrical conduction [3, 6], thermal shock [2, 3], oxidation [5] and fatigue resistance among others. A brittle-to-plas- tic transition occurs at temperatures between 1100 and 1200°C, with large (20%) strains-to-failure in compression, flexure [2] and tension [10]. Transmission electron microscopy (TEM) analysis has shown that dislocations are mobile and multiply during deformation, even at room temperature [7, 11, † To whom all correspondence should be addressed. Tel.: +1-215-895-2338; Fax: +1-215-895-6760. E-mail address: barsoumw@drexel.edu (M. W. Barsoum) 1359-6454/01/$20.00  2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. PII:S1359-6454(01)00243-9 12]. (The basal plane critical resolved shear stresses are estimated to be 36 MPa at room temperature and 22 MPa at 1300°C [8]). The dislocations are overwhelmingly arranged either in arrays, wherein the dislocations exist on identical slip planes (basal planes), or in dislocation walls, wherein the dislo- cations form a low angle grain boundary normal to the basal planes [7]. No other dislocations but perfect, mixed basal plain dislocations with b=1/3112 ¯ 0 [7, 11] are observed by TEM suggesting that only two independent slip systems are available for defor- mation by dislocation glide. Thus, here plasticity does not imply that five independent slip systems are oper- ative, but rather that plasticity is possible by a combi- nation of delamination, kink band formation of indi- vidual grains, as well as shear band formation [2, 4, 7, 8, 10]. The tensile behavior of fine (3–5 μm) grained Ti 3 SiC 2 samples in air is a strong function of tempera-