A phase-field approach to nonequilibrium phase transformations in elastic solids via an intermediate phase (melt) allowing for interface stresses.
A phase-field approach to nonequilibrium phase transformations in elastic solids via an intermediate phase (melt) allowing for interface stresses.
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DOI：
10.1039/c6cp00943c
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发表时间：
2016-04
期刊：
影响因子：
--
通讯作者：
K. Momeni;V. Levitas
中科院分区：
文献类型：
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作者：
K. Momeni;V. Levitas
提出了一种非平衡温度下三相相变的相场方法。它包括先进的力学，一致的界面应力，界面相互作用。一个热力学朗道-金兹伯格潜力开发的极序参数满足所需的不稳定性和平衡条件的均相。尽管采用了小应变假设，但界面应力的引入与大应变公式中的某些项有关。所开发的模型被应用于研究两个固相之间的PT通过一个高度无序的中间相（IP）或中间熔体（IM）数百度以下的熔化温度。特别地，通过IM分析了HMX含能晶体中的β Particles δ PT。研究了不同参数（温度、固-固（SS）-固-熔（SM）界面的宽度和能量比、弹性能和界面应力）对传播SS界面内IM的形成、稳定性和结构的影响。界面和弹性应力内的SS界面相和他们的松弛和重新分布的外观的部分或完整的IM进行了分析。研究了IM临界核的能量和结构。特别是，界面应力增加CN的纵横比。虽然包括弹性能可以大大降低IM的CN的能量，但当考虑界面张力时，SS界面内IM的CN的活化能增加。开发的热力学势也可以被修改，以模拟其他多相物理现象，如多变量马氏体PT，晶界和表面诱导的预熔化和PT，以及开发IP的相图。
A phase-field approach for phase transformations (PTs) between three different phases at nonequilibrium temperatures is developed. It includes advanced mechanics, thermodynamically consistent interfacial stresses, and interface interactions. A thermodynamic Landau-Ginzburg potential developed in terms of polar order parameters satisfies the desired instability and equilibrium conditions for homogeneous phases. The interfacial stresses were introduced with some terms from large-strain formulation even though the small-strain assumption was utilized. The developed model is applied to study the PTs between two solid phases via a highly disordered intermediate phase (IP) or an intermediate melt (IM) hundreds of degrees below the melting temperature. In particular, the β ↔ δ PTs in HMX energetic crystals via IM are analyzed. The effects of various parameters (temperature, ratios of widths and energies of solid-solid (SS) to solid-melt (SM) interfaces, elastic energy, and interfacial stresses) on the formation, stability, and structure of the IM within a propagating SS interface are studied. Interfacial and elastic stresses within a SS interphase and their relaxation and redistribution with the appearance of a partial or complete IM are analyzed. The energy and structure of the critical nucleus (CN) of the IM are studied as well. In particular, the interfacial stresses increase the aspect-ratio of the CN. Although including elastic energy can drastically reduce the energy of the CN of the IM, the activation energy of the CN of the IM within the SS interface increases when interfacial tension is taken into account. The developed thermodynamic potential can also be modified to model other multiphase physical phenomena, such as multi-variant martensitic PTs, grain boundary and surface-induced pre-melting and PTs, as well as developing phase diagrams for IPs.