Transmission electron microscopy of dislocations in cementite deformed at high pressure and high temperature

Abstract

Polycrystalline aggregates of cementite (Fe3C) and (Fe,Ni)3C have been synthesised at 10 GPa and 1250 °C in the multianvil apparatus. Further, deformation of the carbides by stress relaxation has been carried out at temperature of 1250 °C and for 8 h at the same pressure. Dislocations have been characterised by transmission electron microscopy. They are of the [1 0 0] and [0 0 1] type, [1 0 0] being the most frequent. [1 0 0] dislocations are dissociated and glide in the (0 1 0) plane. [0 0 1] dislocations glide in (1 0 0) and (0 1 0). Given the plastic anisotropy of cementite, the morphology of the lamellae in pearlitic steels appears to have a major role in the strengthening role played by this phase, since activation of easy slip systems is geometrically inhibited in most cases.