Pressure effect on the diffusion of carbon at the 85.91^o <100> symmetric tilt grain boundary of α-iron

The diffusion mechanisms (DMs) of C atom around grain boundaries (GBs) in α-iron have long been an area of interest for researchers due to its impact on various mechanical properties for steel such as corrosion resistance and embrittlement. Over the years, these mechanisms have been studied at ambient pressure. However, to date effect of pressure on the DMs of C in GBs of iron has received much less attention and relatively little information is available. In this study, using the kinetic activation-relaxation technique an off-lattice KMC algorithm with on-the-fly catalog building that allows obtaining diffusion properties over large time scales taking full account of chemical and elastic effects coupled with an EAM potential, we investigate the pressure effect on the diffusion properties of C in 85.91^o <100> symmetric tilt GB of α-iron within a range of -1.2GPa to 1.2GPa at a temperature of 600K. We find that, at zero pressure, the C atom segregates to the GB region and traps in energy states lower than found in the crystal. This segregation increases with increasing pressure. Moreover, the effective barriers of C diffusion at the GB increase with increasing pressure. This suggests that at higher pressure C will be pinned by the compression of the boundary, slowing diffusion.