STEADY-STATE DEFORMATION MECHANISM IN TITANIUM CARBIDE

In order to clarify the high-temperature deformation mechanism in titanium carbide during steady state deformation, specimens prepared by r.f. zone melting technique were deformed by compression at temperatures from 1745 to 2270 K and at strain rates from 2 x 10(-5) to 5 x 10(-3) s-1, and the dislocation structure after deformation was observed by transmission electron microscopy. It is found that the activation energy for steady state deformation is 560 kJ/mol, which is about 3/4 of that for lattice self-diffusion of Ti in TiC, and the stress exponent, m(s), for steady state strain rate is about 7 in a temperature range of 1745 to 2125 K and about 5 at 2270 K. The dislocation structure consists of subboundaries and networks in subgrains. The rate-controlling mechanism in the steady state deformation is discussed on the basis of the dislocation network model and it is suggested that the network growth should be controlled by the pipe-diffusion of Ti along dislocations in the lower temperature range where m(s) is 7, while the growth should be controlled by the lattice self-diffusion of Ti in the higher temperature range where m(s) is 5.