EARLY STAGES OF NANOSTRUCTURING OF A PEARLITIC STEEL BY HIGH PRESSURE TORSION DEFORMATION

摘要

High-pressure torsion of a pearlitic steel under a pressure of 7 GPa and for 1 rotation produces a highly deformed pearlitic structure. Some regions are less deformed with straight lamellae and resolvable dislocations, whereas other have more buckled lamellae and the ferrite appears to have a nanoscale cell structure with each cell slightly misoriented from its neighbours. In all cases, the cementite lamellae still contain most of the carbon but are broken into a nanocrystalline structure. 3D atom probe analyses show that the cementite is losing carbon, and that some of this appears to be transported along dislocations into cell wall structures. The deformation mechanisms and the early stages of the destruction and dissolution of the cementite are discussed.