Tensile creep of coarse-grained Ti 3SiC 2 in the 1000–1200 °C temperature range

Abstract

The tensile creep of coarse-grained, CG, Ti 3SiC 2 samples, in the 1000–1200 °C temperature, T, and 10 MPa to 100 MPa stress, σ, ranges, respectively, was studied. The creep behavior is characterized by three regimes: an initial, a secondary where the creep rate is at a minimum, ε min , and a tertiary regime. In the intermediate regime ε min is given by: ε min ( s −1)=ε o exp 17±1 σ σ o 2.0±0.1 exp −458±12 kJ/mol RT where σ 0=1 MPa and ε 0=1 s −1. The times to failure are given by: t f (s)=exp(−2±0.3) ε min −1 . The results presented herein confirm that: (a) dislocation creep is the dominant mechanism; (b) the high plastic anisotropy of Ti 3SiC 2 results in large internal stresses during creep; (c) the response is dictated by a competition between the rates of generation and dissipation of these internal stresses; (d) at higher temperatures and/or lower strain rates the internal stresses can dissipate and the behavior is more ductile. Furthermore, in the tertiary creep regime, the creep appears to occur by a combination of dislocation creep and the formation of cavities and cracks. The coarse-grained samples have lower creep rates than their fine-grained (3–5 μm) counterparts, and their times to failure are longer. The latter is partially attributable to the ability of the larger grains, whose basal planes are normal to the applied load, to form tenacious crack bridges by delamination and kink band formation, in addition to the bridges that occur when the basal planes are parallel to the applied load.