Estimation of austenite grain boundary mobility in low-carbon steel by grain growth

The temporal evolution of grain size distribution (GSD) was observed by EBSD IPF maps of austenite reconstructed from the orientation maps of martensite in Fe–0.1C and Fe–0.1C–3Mn alloys from which the spatial GSD was predicted by the Saltykov method. They were compared with grain growth simulation by Abbruzzese and Lücke (A–L) model. The mobility of grain boundary in the Fe–0.1C alloy was estimated to be three to four orders of magnitude lower than those of ferrite grain boundaries of high-purity Fe, similar to or somewhat lower than the higher values of α / γ interface reported so far. The spatial GSD and average grain radius in the Fe–0.1C–3Mn alloy were compared with the A–L model in which solute drag caused by carbon and Mn segregation was incorporated. The grain growth rate was reproduced with the Mn diffusivity across a grain boundary, i.e. trans-grain boundary diffusion coefficient, lying between the volume diffusivity of Mn in austenite and the diffusivity along the grain boundary.