Evolution of a generic two-dimensional grain structure as a model for grain growth in microalloyed steels
The two dimensional space is tessellated by unit cells that consist of a four-sided, two six-sided and an eight-sided grain. Finite mobilities can be assigned to each of the grain boundaries of the unit cell and the mobilities of the triple points (i.e. the crossing point of three grain boundaries) can also be set to finite values. Thereby, solute drag influenced grain boundary migration is simulated as it e.g. occurs during grain growth in microalloyed steels. It is demonstrated that it strongly depends on the location of the triple point or on the grain boundary within the grain boundary arrangement whether a reduced mobility has a strong or a low impact on the kinetics of grain growth. A difference in the mobilities of the entities of the microstructure may result in highly distorted grain structures. Strongly curved grain boundaries are adjacent to almost straight grain boundaries. It is shown that the size distribution of the grains becomes broader when reducing all triple point mobilities of the system. Furthermore, some grains become strongly elongated in case of reduced mobilities of grain boundary entities. Such microstructural features were also observed in micrographs of microalloyed steels after being heat treated at those elevated soaking temperatures where a transition to abnormal grain growth is expected in case of extended holding times.