5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

After solidification, grain growth occurs in the metallic materials, in general. It is very important to understand grain growth as well as solidification in order to control the mechanical properties of metallic materials. Abnormal grain growth(AGG), in which some grains preferentially grow to be extremely large, often occurs during cooling and isothermal holding at high temperatures after the solidification. AGG is related to non-uniformity of secondary phase particles and/or change in their distribution with time. Since AGG degrades mechanical properties, it is necessary to elucidate the mechanism and condition for occurrence of AGG. The precipitates in matrix and also remaining liquid in solidification serve as the second phases associated with AGG and the size of such pinning particles is often much smaller than the grain size of the matrix. Phase-field models have been utilized for simulating pinning effects on grain growth. However, early models cannot be applied to analysis of pinning effect and AGG when the pinning particle is very small compared with the grain size of matrix. This is because the pinning particles are explicitly described in the early models and hence the simulation of grain growth with very fine particles requires huge computational cost. Therefore, in this study, the pinning effects of particles are introduced in the phase-field model based on a mean-field approximation. The present model can reproduce the curvature driven motion of grain boundary with pinning force. Using this model, we investigate occurrence of AGG in carbon steels under various heat treatments.