Nucleation and Growth of Solid-State Transformations

固态转变的成核和生长

• 批准号: 9122081
• 负责人: Gregory Olson
• 金额: $ 38.73万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-03-01 至 1995-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9122081&HistoricalAwards=false
• 关键词: Nucleation; Growth; Solid; State; Transformations

This research program is directed towards improved understanding of first-order phase transformations based on examination of the martensitic phase transformation. The program employs both theoretical and experimental approaches to address two broad areas: (a) the distributed-activation kinetics of heterogeneous nucleation; and (b) competing transformation mechanisms in nonlinear nonlocal solids. General features of distributed- activation heterogeneous kinetics are examined in nucleation kinetic experiments employing acoustic emission and sterological measurements in both thermoelastic and nonthermoelastic martensitic systems, defining potency distributions of initial and autocatalytic defects. principles are extended to bainitic transformations and solidification. Competing mechanisms of structural transformation are examined by combined theory and experiment in model systems describable by nonlinear nonlocal continuum models predicting interfacial energies. Experiments test predicted behavior of a new transformation mechanism, quasimartensitic strain modulation, which competes with nucleation and growth under conditions near a lattice instability. %%% This analytical and experimental work is directed to martensitic transformations found in steels, for instance, but is applicable to other phase transformations in metals and ceramics.

本研究项目旨在通过对马氏体相变的研究，提高对一阶相变的理解。该计划采用理论和实验方法来解决两个广泛的领域：(a)非均相成核的分布活化动力学；(b)非线性非局部固体中的竞争转化机制。在热弹性和非热弹性马氏体体系的成核动力学实验中，采用声发射和体学测量方法研究了分布活化非均相动力学的一般特征，定义了初始缺陷和自催化缺陷的势分布。原理推广到贝氏体相变和凝固。采用理论与实验相结合的方法，研究了用非线性非局部连续模型预测界面能的模型系统中结构转化的竞争机制。实验测试预测了一种新的转变机制——准马氏体应变调制的行为，它在晶格不稳定的条件下与成核和生长竞争。例如，这项分析和实验工作针对的是在钢中发现的马氏体相变，但也适用于金属和陶瓷中的其他相变。