Kinetics of Phase Transformations

相变动力学

• 批准号: 8919235
• 负责人: William Klein
• 金额: $ 41.04万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-06-01 至 1993-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8919235&HistoricalAwards=false
• 关键词: Kinetics; Phase; Transformations

This grant is a combined experimental and theoretical examination of phase transformations in materials. Fast (millisecond ) synchrotron-based time resolved X-ray scattering is employed to study spinodal decomposition and ordering in alloys. Preliminary research has concentrated on the classic cases of spinodal decomposition in aluminum-zinc and ordering in copper-gold and showed that there is no significant timescale during which the Cahn-Hilliard-Cook linear theory or its extension, the Langer-Bar-On-Millier nonlinear theory are valid. Now the research is centered on alloys with smaller strain effects (iron-chromium and iron-cobalt), alloys with second-order ordering transitions (iron-cobalt and aluminum-iron), and alloys that undergo simultaneous ordering and phase separation (aluminum-iron). In some of these cases these fast experiments probe transformation kinetics in regions of the phase diagram in which neither phase is the true equilibrium structure. The simulations and theory part of the research pursues large scale studies of spinodal decomposition and continuous ordering in both Ising models and fluids, for short and long range interactions. Included are studies of crystallization in simple fluids. Limits of the present nucleation theories are studied by taking simulation data as the limit of miscibility is approached and seeing where the theory begins to fail. Geometric models are developed for nucleation and spinodal decomposition

该资助是对材料相变的实验和理论相结合的检验。 基于快速（毫秒）同步加速器的时间分辨 X 射线散射用于研究合金中的旋节线分解和排序。 初步研究集中在铝-锌中的旋节线分解和铜-金中的有序化的经典案例，并表明Cahn-Hilliard-Cook线性理论或其扩展、Langer-Bar-On-Millier非线性理论不存在有效的显着时间尺度。 现在的研究集中在应变效应较小的合金（铁-铬和铁-钴）、具有二阶有序转变的合金（铁-钴和铝-铁）以及同时进行有序和相分离的合金（铝-铁）。 在其中一些情况下，这些快速实验探测相图区域中的转变动力学，其中两相都不是真正的平衡结构。 该研究的模拟和理论部分致力于对伊辛模型和流体中的短程和长程相互作用的旋节线分解和连续排序进行大规模研究。 其中包括简单流体中结晶的研究。 通过在接近混溶性极限时获取模拟数据来研究当前成核理论的局限性，并查看该理论在哪里开始失效。 为成核和旋节线分解开发了几何模型