Dislocation glide motion in 6H SiC single crystals subjected to high-temperature deformation

Abstract

SiC single crystals of 6H polytype were plastically deformed by uniaxial compression at a constant strain rate at temperatures between 1100 and 1800°C, and their critical resolved shear stress τ_c and strain-rate sensitivity were measured as a function of temperature. The flow rate [ydot] was found to be expressible in the form [ydot] (τ_c − τ_i) ⁿ exp (−U/kT), where the activation energy U, the stress exponent n and the stress τ_i were evaluated to be 3·4 ± 0·7 eV, 3·1 ± 0·4 and 3 MPa, respectively. The present study indicates that plastic strain of the SiC crystals under the present deformation conditions was due to dislocation glide motion on the basal slip system. The motion also appears to have been the rate-controlling process of plastic flow. It is concluded through quantitative reasoning that, in the temperature range studied, the basal dislocation motion is dominated by the Peierls mechanism rather than by the solution-hardening mechanism.