Effect of C/Ti Atom Ratio on the Deformation Behavior of TiCχ Grown by FZ Method at High Temperature

Abstract

In order to clarify the effect of C/Ti atom ratios(χ) on the deformation behavior of TiC χ at high temperature, single crystals having a wide range of χ, from 0.56 to 0.96, were deformed by compression test in a temperature range of 1183~2273 K and in a strain rate range of 1.9 × 10 −4~5.9 × 10 −3 s −1. Before testing, TiC χ single crystals were grown by the FZ method in a He atmosphere of 0.3 MPa. The concentrations of combined carbon were determined by chemical analysis and the lattice parameters by the X-ray powder diffraction technique. It was found that the high temperature deformation behavior observed is the χ-less dependent type, including the work softening phenomenon, the critical resolved shear stress, the transition temperature where the deformation mechanism changes, the stress exponent of strain rate and activation energy for deformation. The shape of stress-strain curves of TiC 0.96 , TiC 0.85 and TiC 0.56 is seen to be less dependent on χ, the work hardening rate after the softening is slightly higher in TiC 0.96 than in TiC 0.85 and TiC 0.56 . As χ decreases the work softening becomes less evident and the transition temperature where the work softening disappears, shifts to a lower temperature. The τ c decreases monotonously with decreasing χ in a range of χ from 0.86 to 0.96. The transition temperature where the deformation mechanism changes shifts to a lower temperature as χ decreases. The activation energy for deformation in the low temperature region also decreased monotonously as χ decreased. The deformation in this temperature region is thought to be governed by the Peierls mechanism.