Generating Triple Junction Distributions
Hardy, Graden Bryant
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Substantial studies indicate polycrystalline triple junctions are independent microstructural defects with distinct properties and effects from their constituent grain boundaries. Triple junctions are also descriptive of grain boundary networks and can provide relative grain boundary energies. Despite their undeniable influence within microstructures, there is a lack of techniques for characterizing triple junctions on a large scale. This is the result of the difficulty of measuring their many parameters and three-dimensional features. In a first step towards triple junction characterization, this work has developed a method of characterizing twin-dependent triple junction distributions. All necessary parameters and conventions are established for generating twin-dependent distributions within a discrete space. A novel method of weighting distribution values to remove inherent sampling biases is developed. As a result of the distribution weighting, a novel technique for generating twin-dependent triple junctions with unequal volume cells is created. Grain boundary plane stereological methods are adopted to enable forming twin-dependent distributions from electron back-scatter diffraction data on a single section plane. This method has been prepared in a software format for the automated generation of distributions. The method has been optimized by empirical techniques and through the implementation of simulated microstructures it has been qualitatively and quantitatively validated. Quantitative measures of distribution quality are developed and implemented to approximate the relative reliability of results with respect to data quantity. The implications of this method to general triple junctions are discussed and the parameters and conventions of a general triple junction distribution are presented as a foundation for future development. This work prepares the fundamentals to general triple junction characterization and makes progress towards integrated materials engineering.