Persistence of abnormal grain growth in the presence of grain boundary complexion transitions: Thermodynamic analysis and phase field modeling

An anomalous feature in polycrystalline grain growth in metals and ceramics is the rapid abnormal growth of a few grains relative to the surrounding matrix grains. In certain systems, this phenomenon is reported to be associated with the presence of first order phase transitions in the grain boundaries often referred to as complexion transitions. The fundamental question of how the growth advantage of abnormally growing grains persists in this context is not yet well understood. We present a thermodynamically consistent mechanism by which abnormal grain growth may occur. The presence of two complexion transitioned boundaries at a triple junction provides a driving force for partial wetting at the triple junction leading to the formation of a quadruple junction. The subsequent dissociation of the quadruple junction into two partial wetting triple junctions favors the persistence of abnormal grain growth. We incorporate this dissociation process into a multi-order parameter phase field model and demonstrate the occurrence of abnormal grain growth without the need for mobility advantage or additional driving forces. The results from simulations of abnormal grain growth capture experimentally observed microstructural features such as peninsular and island grains. Through a systematic study we show that the initial fraction of complexion boundaries plays a significant role in abnormal grain growth and that maximum abnormal grain growth is observed when the fraction of complexion boundaries is less than about 2%.