Quantification of Microstructural Evolution in Grain Boundary Networks

In this work, the effect of grain boundary engineering (GBE) on the structure and connectivity of networks of two types of boundaries was quantified. General high angle boundaries and “special” Σ = 3 and Σ = 9 coincident site lattice boundaries were considered. The effect of GBE processing was to increase the population and length of special boundaries and to disrupt the network of high-angle grain boundaries (HAGBs) in the microstructure. The GBE processing resulted in an increase in the population of special boundaries as determined by line length fraction from approximately 37% to approximately 57%. The connectivity of the special boundaries, as determined by topological analysis, increased by a factor of 4, while the connectivity of HAGBs decreased by an order of magnitude. Cluster sizes in the special boundary network increased across the range of sizes, and the maximum cluster size of HAGBs decreased significantly. The metrics reported here allow for a quantitative analysis of grain boundary connectivity in microstructures, as well as for a quantitative means of comparison of microstructures. These metrics will be used in simulations of diffusional creep, with the aim of quantifying structure–property relationships in grain boundary engineered systems.