Phase Field Model Simulation of Abnormal Grain Growth by Solid-State Wetting

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Abnormal grain growth (AGG) takes place in many metallic systems especially after recrystallization of deformed polycrystals. The growth advantage has been attributed to the high mobility of the grain boundaries of the abnormally-growing grains. As a new approach to the growth advantage of AGG, however, we suggested the solid-state wetting, where a grain wets or penetrates the grain boundary or the triple junction of neighboring grains just as the liquid phase wets along the grain boundary or the triple junction. If the energy sum of the two grain boundaries is lower than the energy of the other grain boundary in contact at the triple junction, the high energy grain boundary will be replaced by the two low energy grain boundaries through the wetting process. Once the solid-state wetting occurs, the triple junction, which tends to be a rate-determining step in grain growth, migrates much faster than the grain boundaries in contact and therefore, the triple junction constraint in grain growth disappears. Here, we studied the effect of solid-state wetting on AGG by phase field model (PFM) simulation and compared the microstructural feature of AGG with that observed experimentally in Fe-3%Si alloy. The misorientation angles between island and peninsular grains accompanied by AGG were measured using electron backscattered diffraction (EBSD). The PFM simulation shows the realistic microstructural evolution of island and peninsular grains during AGG by solid state wetting. Very high frequency of island and peninsular grains formed at or near the growth front of abnormally growing grains could be best explained by solid-state wetting.