Numerical Analysis of the Effect of Diffusion and Creep Flow on Cavity Growth at the Nano-scale Level
F.W. Brust and J. Oh
Battelle Memorial Institute, US
high temperature, cavity growth, diffusion, creep flow, intercrystalline fracture
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. In summary, a unified numerical method for cavity growth, where combined effects of deformation and two distinct diffusion mechanisms are considered, is presented. Given the stress state in the neighborhood of the grain boundary, this numerical method provides detailed microscopic analysis of cavity growth including the change in geometry and size.
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Nanotech 2005 Conference Program Abstract