Effect of thermal activation and vibrational dynamics of dislocations on thermodynamic dislocation theory

位错的热激活和振动动力学对热力学位错理论的影响

• 批准号: 447038308
• 负责人: Dr.-Ing. Yinguang Piao
• 金额: --
• 依托单位: Department of Mechanical Engineering
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/447038308?language=en
• 关键词: Effect; thermal; activation; vibrational; dynamics

Processed metals have been used by human beings for more than 5000 years since the bronze age. Plastically deformed metals have some beneficial properties, such as high strength and irreversibility, as tools and weapons to be used. Dislocations, as line defects, are the primary carriers of plastic deformation in crystals and dislocation‘s motion, interaction and annihilation influence remarkably the mechanical behaviour of materials. Despite the long history of empirical processing technology in metals and 70 years since dislocations were observed, we still lack fundamental theories of dislocation substructure development and its relation to hardening responses. Recently, the entropy of dislocations microstructures is involved into material modelling, which is believed to compensate for this “lack of knowledge”. In 2010 Langer, Bouchbinder, and Lookman have proposed thermodynamic dislocation theory involving entropy of dislocations. Using this theory with a set of few physics-based parameters, the numerous stress-strain curves in plane strain compression for copper, aluminum and steel over several decades of strain rate and from room temperature to one half of melting point have been simulated and obtained quantitative agreements with experimental results, which attested the usefulness of the theory. In addition to the applications in macroscopic engineering, one attempt to explore microstructures and associated mechanical responses, has been made through introducing excess dislocations, and the kinematic hardening, Bauschinger effect, and size effect based on the physical mechanism of movement of excess dislocations have been explained. Thermodynamic dislocation theory still has spaces to develop to account for hierarchy of material structures, such as to involve the interactions of dislocations to other material defects, e.g. vacancies, grain boundaries, precipitates. Since only depinning mechanism, a controlling feature of dislocation-dislocation interaction, is used in the theory, it may be valid in single phase metals but insufficient in others. For precipitate of multiphase strengthened alloys in practice, thermal activated bypass of barriers owing to the vibration of dislocation system plays important role. Thus, the main target of my project is to develop an extension of thermodynamic dislocation theory for hardening induced by precipitates. Two objectives become of prime interest, (i) adoption of the effect of thermal vibration of dislocation lines into the theory and (ii) involvement of dislocation bypass mechanism.

自青铜时代以来，加工金属已被人类使用了 5000 多年，塑性变形金属具有一些有益的特性，例如高强度和不可逆性，作为工具和武器，位错（作为线缺陷）是主要的。尽管金属的经验加工技术已有很长的历史，自位错出现以来已有 70 年的历史，但晶体中的塑性变形载体和位错的运动、相互作用和湮灭对材料的机械行为有重大影响。据观察，我们仍然缺乏位错亚结构发展及其与硬化反应的关系的基本理论。最近，位错微观结构的熵被纳入材料建模中，这被认为可以弥补这种“知识的缺乏”。2010年，Langer，Bouchbinder，和卢克曼提出了涉及位错熵的热力学位错理论，使用该理论和一组基于物理的参数，可以得出铜、铝和铝的平面应变压缩中​​的大量应力-应变曲线。对钢在几十年的应变速率和从室温到二分之一熔点的变化进行了模拟，并与实验结果获得了定量的一致性，这证明了该理论除了在宏观工程中的应用之外，也是探索微观结构的一种尝试。以及相关的机械响应，已经通过引入过量位错来实现，并且基于过量位错运动的物理机制的运动硬化、包辛格效应和尺寸效应已经得到解释，热力学位错理论仍有待发展的空间。对于材料结构的层次结构，例如涉及位错与其他材料缺陷（例如空位、晶界、析出物）的相互作用，由于理论中只使用了脱钉机制（位错-位错相互作用的控制特征）。在单相金属中有效，但在其他金属中则不足。对于实际中的多相强化合金的沉淀，由于位错系统的振动而引起的势垒的热激活旁路起着重要作用。因此，我的项目的主要目标是开发。析出物引起硬化的热力学位错理论的扩展引起了人们的主要兴趣，（i）将位错线的热振动效应纳入理论中；（ii）涉及位错旁路机制。