Fig. 12 Growth process of dislocations on the interface when d3 is applied along the y -axis. The whole process is contained in the first quarter of the first cycle. (a) timestep=11.2ps, d=9.766Å. (b) timestep=12.0ps, d=10.172Å. (c) timestep =12.8ps, d=10.522Å. (d) timestep =13.6ps, d=10.816Å. Green and blue lines in bcc-Fe matrix correspond to 1/2<111> and <110> dislocations, respectively. (e) Viewing area and orient of the dislocation growth. The view is kept parallel to the interface by rotating the coordinate system.
Severe shear deformation leads to excessive growth of dislocations which evolve into surface defects such as stacking fault, and the interlaced dislocations ultimately result in irreversible plastic accumulation. Note that the nucleation of dislocations usually occurs on the interface between bcc-Fe and cementite. Therefore, it is convincing that the generation and accumulation of dislocations on the two-phase interface or the boundary of carbide inclusions are the origin of the cyclic plastic accumulation. This may also be the main reason why bearing steels damage usually appears near inclusions such as carbides.