作者: Ke Gang Wang, X. Ding

摘要: The dynamics of phase coarsening at ultra-high volume fractions is studied based on two-dimensional phase-field simulations by numerically solving the time-dependent Ginzburg-Landau and Cahn-Hilliard equations. The kinetics of phase coarsening at ultra-high volume fractions is discovered. The microstructural evolutions for different ultra-high volume fractions are shown. The scaled particle size distribution as functions of the dispersoid volume fraction is presented. The particle size distribution derived from our simulation at ultra-high volume fractions is close to Wagner's particle size distribution due to interface-controlled ripening rather than Hillert's grain size distribution in grain growth. The changes of shapes of particles are carefully studied with increase of volume fraction. It is found that more liquid-filled triple junctions are formed as a result of particle shape accommodation with increase of volume fraction at the regime of ultra-high volume fraction.

3925

作者: Yuhki Tsukada, Yoshinori Murata, Toshiyuki Koyama, Masahiko Morinaga

摘要: A phase-field simulation is performed to examine the effect of elastic inhomogeneity between the and ’ phases on coarsening of the ’ phase in Ni-based superalloys. In the calculation of elastic strain energy, the mechanical equilibrium equation in elastically inhomogeneous system is solved by an iterative-perturbation scheme. On the basis of the elastic constants of a practical Ni-based superalloy, a series of simulations is performed in which both elastic anisotropy and shear modulus are varied independently. The variation of elastic anisotropy gives significant effect on both morphology and size distribution function of the ’ particles, whereas the variation of shear modulus gives little effect on them. Furthermore, it is found that the coarsening rate constant of the cubic growth raw changes and increases with increasing the standard deviation of the ’ size distribution.

376

作者: Chang Bo Ke, Bao Zhong Xie

摘要: The effect of initia gamma prime particle size on coarsening kinetics of gamma prime precipitates in Nickel-based superalloys has been studied by means of phase field method which takes into account the lattice misfit. The simulation shows that the gamma prime precipitate morphology at the late stage of coarsening is independent of initial particle size, and the rectangle-like precipitates dominate the matrix which is in good agreement with experimental studies. The coarsening exponent increases with initial size, while the coarsening rate constant exhibits no apparent regularity. Although the coarsening trend is independent of initial particle size, the precipitate size increases with initial size at a given aging time. Through precipitate size distribution calculation, it is found that the size distribution is fairly stable, which is not sensitive to the initial particle size.

1834

作者: Shui Qing Xiao, Shang Hua Wu

摘要: Mechanical properties of ceramic materials are closely related to the grain size, and control the ceramic material grain size is the key to increase mechanical properties of materials. Study on the theory of ceramic sintering grain growth model, such as solid phase sintering, liquid phase sintering and master sintering curve (MSC) and so on. Grain growth model not only can be used to guide the actual production design, but also can be used as a computer simulation tools. It is suggest that before use any grain growth model must modify their express from traditional model, and check the equation is correct that it is agree with the result of re-experiment.

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