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

摘要

Polycrystalline aggregates of cementite (Fe3C) and (Fe,Ni)(3)C have been synthesised at 10 GPa and 1250 degrees C in the multianvil apparatus. Further, deformation of the carbides by stress relaxation has been carried out at temperature of 1250 degrees 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.