Molecular dynamics simulation of the effect of cementite decomposition on yield phenomena in pearlite microstructure

Molecular dynamics simulations were used to investigate cementite decomposition's effect on ferrite/cementite interface-mediated plastic deformation. To model the cementite decomposition, an amorphous cementite phase is introduced between the ferrite and cementite layers with the Bagaryatski orientation relationship. The effects of the cementite decomposition on two plastic deformation phenomena are investigated by varying the thickness of the amorphous cementite layer: first, dislocation emission from the interface, and second, plastic deformation propagation from the ferrite phase to the cementite phase. The introduction of amorphous cementite into a ferrite/cementite interface containing interfacial dislocations causes the effective dislocation nucleation site originating from the interfacial dislocation to lose function, increasing the yield stress of the ferrite/cementite microstructure. The thicker the amorphous layer, the more difficult it is for the ferrite-phase plastic deformation to propagate to the cementite phase. These results suggest that cementite decomposition complicates plasticity phenomena at the interface. The effect of cementite decomposition on the work-hardening ability of the ferrite phase is discussed, as is the possibility of achieving both high strength and high ductility in drawn pearlite steel via appropriate interface structure design. (author)