Nana-scale Level Numerical Analysis of the Effect of Diffusion on Cavity Growth of Advanced Materials

Keywords:
high temperature, high pressure, creep damage, diffusion, cavity growth

Abstract:
One of the main future uses of nano-materials is for very high temperature response and management. Many processes today are inefficient because the costs of operating at such high temperatures are not manageable. Diffusion and cavity growth of nano-materials will continue to be life limiting factors as systems are built from the nano-scale. Indeed, many failures occur because of mis-management of high temperatures and pressures inherent in many structural systems. Many times these failures receive extensive press coverage as well (e.g., Columbia failure). At high temperature, cavity initiation and cavity growth are important phenomena in understanding the failure mechanism and in predicting the lifetime of various parts in service in the area of power plants, aerospace applications, among others. Such nucleation and growth phenomena are explained by diffusion of atomic flux (from cavity surface to grain boundary), creep flow, and grain boundary sliding. Cavity growth leads to cavity coalescence, and then grain boundary rupture occurs. Because of the complexity of the physical phenomenon, in most of the numerical work, one of the two extreme cases, fast grain boundary diffusion or fast surface diffusion, with or without the consideration of grain material deformation, is assumed. However, there has not been any unified cavity growth rate analysis where the combined effects of creep flow and surface/grain boundary diffusion mechanisms on cavity growth are considered. An understanding of, and predictive models to assess the high temperature response of materials is a critical step as nano-built materials are used in industry.

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Nanotech 2006 Conference Program Abstract