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M. Asle Zaeem,H. El Kadiri,M.F. Horstemeyer,M. Khafizov,Z. Utegulov 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Phase stability, topology and size evolution of precipitates are important factors in determining the mechanical properties of crystalline materials. In this article, the CahneHilliard type of phase-field model was coupled to elasticity equations within a mixed-order Galerkin finite element framework to study the coarsening morphology of coherent precipitates. The effects of capillarity, particle size and fraction,compositional strain, and inhomogeneous elasticity on the kinetics and kinematics of coherent precipitates in a binary dual phase crystal admitting a third intermediate stable/meta-stable phase were investigated. The results demonstrated the ability of the model to simulate coarsening under the concomitant action of Ostwald ripening and mismatch elastic strain mechanisms. Using a phenomenological coarsening power law, coarsening rates were determined to depend on precipitate size and volume fraction, compositional strain, and strain mismatch between precipitates and the matrix. Results also showed that the necking incubation time between two neighboring precipitates depends inversely on the precipitate’s initial sizes; however, under fixed volume fraction of precipitates, any increase in the initial sizes of the precipitates mitigates the coarsening. Meanwhile, the compositional strain and the growth of the intermediate stable/meta-stable phase leads to substantial enhancements of precipitate coarsening.
Investigation on Sintering Mechanism of Nanoscale Tungsten Powder Based on Atomistic Simulation
Amitava Moitra,Sungho Kim,Seong-Gon Kim,Seong Jin Park,Randall M. German,Mark F. Horstemeyer 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Atomistic simulations focusing on sintering of crystalline tungsten powders at the submicroscopic level are performed to shed light on the processing on the nanoscale powders. The neck growth and shrinkage were calculated during these sintering simulations, so it is possible to extend these results to the global physical property evolution via sintering. The densification and grain growth during sintering were calculated with variations in temperature, pressure, particle configuration, additives, and crystalline misalignment between particles. These findings lay a foundation for a virtual approach to setting the processing cycles and materials design applicable to nanoscale powders.