Predicting Grain Growth in Nanocrystalline Materials:A Thermodynamic and Kinetic-Based Model Informed by High Temperature X-ray Diffraction Experiments

Report No. ARL-TR-7107
Authors: Mark A Tschopp; Kris A Darling; Mark A Atwater; Kiran N Solanki
Date/Pages: October 2014; 79 pages
Abstract: Predicting grain growth in nanocrystalline materials requires modeling approaches that incorporate grain boundary thermodynamics and kinetics. In this work, a thermokinetic model for grain growth was applied to experimental X-ray diffraction measurements from nanocrystalline Fe–Zr in an effort 1) to understand the influence of thermodynamic, kinetic, and material parameters in the model; and 2) to extend the thermokinetic model by incorporating temperature dependence. The model performs well for the grain boundary saturated case in the nanocrystalline Fe–Zr system, where Zr segregate to the Fe grain boundaries and thermodynamically/kinetically reduce the driving force for grain growth. In this work, a sensitivity analysis of parameters (Monte Carlo global sensitivity analysis with 10,000 instantiations) identifies the important thermodynamic/kinetic parameters for the model. This model was then extended to include the change in these independent thermodynamic/kinetic parameters as a function of temperature and to model the effect of grain size distribution. The significance of this research is that the thermodynamic and kinetic contributions may be necessary to help explain grain growth in nanocrystalline materials and this extended model can be applied to understanding how grain size evolves with temperature in other nanocrystalline systems.
Distribution: Approved for public release
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Last Update / Reviewed: October 1, 2014