Nucleation of recrystallization in fine-grained materials: an extension of the Bailey–Hirsch criterion

Abstract

A new criterion for nucleation in the case of dynamic recrystallization is proposed in order to include the contribution of the grain boundary energy stored in the microstructure in the energy balance. Due to the nucleation events, the total surface area of pre-existing grain boundaries decreases, leading to a nucleus size smaller than expected by conventional nucleation criteria. The new model provides a better prediction of the nucleus size during recrystallization of pure copper compared with the conventional nucleation criterion.     

Crystal growth velocity in deeply undercooled Ni–Si alloys

The crystal growth velocity of Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T _L?≈?1505 and 1387?K for Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni–Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10?at.% Si, resulting in the remarkable decrease of growth velocity.     

加速的体验性动力学心理治疗的现状与进展

通过对加速的体验性动力学心理治疗的理论基础、理论模型、治疗策略进行综述与分析,阐明了心理治疗的基本架构。聚焦转化力和促进转化是治疗的根本;最差自体行使功能（精神病源）模型与最佳自体行使功能（蓬勃成长）模型是解释最差自体和最佳自体形成的理论基础;22个治疗策略是促进核心情感体验、建立安全依恋关系以及最终实现治疗目标的具体方法。通过对加速的体验性动力学心理治疗实证与理论研究最新进展的介绍,证实了治疗的有效性和先进性,并总结了7个显著贡献。