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45475-AC10
Statistical Theories of Failure in Polycrystalline Materials

Phillip M. Duxbury, Michigan State University

Grain boundary networks are engineered by increasing the fraction of boundaries which exhibit improved properties. Favorable boundaries have either low grain boundary misorientation or they are special boundaries, such as coincident site lattice boundaries. Significant improvement in properties such as corrosion resistance, critical current in superconductors and mechanical strength and toughness occur, provided percolating grain or grain boundary structures can be engineered. We have developed computational models for grain boundary engineered polycrystals and demonstrated that grain boundary constraints modify the behavior near the percolation threshold. We postulate that this is due to an enhanced clustering of weak boundaries induced by grain boundary constraints. In random grain structures the fraction of strong grain boundaries may be measured in two ways, either the length fraction, c, or the edge fraction

ce. We find that grain boundary constraint shifts the length fraction threshold,

c*, of Potts model polycrystals to higher values, while the edge fraction, ce*, remains almost the same in both correlated and uncorrelated grain structures.

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