PHASE-FIELD MODELING OF SOLUTE SEGREGATION TO STACKING FAULT DURING PARTIAL DISLOCATION GLIDE

Abstract

This study presents a phase-field model of partial dislocation glide along with concurrent solute segregation to stacking fault. Many authors related to this field have shown that the diffusion mechanism by virtue of different crystal structure of stacking fault and bulk material has occurred along the fault plane. In our model, we are considering solute diffusion occurs by above said mechanism. Segregation of solute atoms to the stacking fault lowers the stacking fault energy (SFE) and facilitates further movement of the leading partial dislocation (LPD). The purpose of the current work is also to study the variation of LPD velocity as a function of applied shear stress under simultaneous Suzuki segregation along with the LPD motion. We present the model formulation in steps. At first, the model of partial dislocation glide is formulated, followed by solute partitioning along the fault plane. We run simulations for dilute alloy binary solution where the amount of solute is quite low when SFE is a function of composition and at constant SFE. The simulation determines the stacking fault composition profile, captures the distance moved by the LPD and also its velocity at various applied shear stress (σb). A minimal difference in the velocity (v) vs shear stress (σb) curve between the case when SFE is a function of composition and at constant SFE has observed in dilute alloy solution at low shear stress. That motivates us to consider an ideal solution alloy having a considerable amount of solutes. Simulations for ideal solution alloy was also run for the two cases of SFE. A convergence between the curve of SFE as a function of composition with constant SFE in v vs σb plot has observed as moving from lower σb to the higher σb side. This convergence is because of the incomplete partitioning, as the chance of solute trapping is very high at higher LPD velocity, increasing the SFE. The present research work further advances in developing a phase-field model for the case of multi-component alloy.