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，人类使用加工金属已有5000多年的历史。塑性变形金属具有一些有益的特性，如高强度和不可逆性，可用作工具和武器。位错是晶体中塑性变形的主要载体，位错的运动、相互作用和湮灭对材料的力学行为有着重要的影响。尽管金属的经验加工技术历史悠久，观察到位错已有70年，但我们仍然缺乏位错亚结构发展及其与硬化反应关系的基本理论。最近，位错微结构的熵被纳入材料建模，这被认为是弥补这种“知识的缺乏”。 2010年，Langer、Bouchbinder和Lookman提出了包含位错熵的热力学位错理论。利用该理论，在较少的物理参数下，对铜、铝和钢在几十年应变速率下从室温到半熔点的平面应变压缩应力-应变曲线进行了数值模拟，得到了与实验结果定量吻合的结果，证明了该理论的实用性。除了在宏观工程中的应用外，还尝试通过引入过量位错来探索微观结构及其力学响应，并解释了基于过量位错运动物理机制的随动硬化、Bauschinger效应和尺寸效应。 热力学位错理论仍有发展空间来解释材料结构的层次，例如涉及位错与其他材料缺陷的相互作用，例如空位，晶界，沉淀物。由于该理论只考虑了位错-位错相互作用的一种控制机制--脱钉机制，因此该理论在单相金属中可能是有效的，但在其他金属中则是不够的。在实际应用中，对于多相强化合金的析出，位错系统振动引起的势垒热激活旁路起着重要作用。因此，我的项目的主要目标是发展一个扩展的热力学位错理论的析出物诱导硬化。两个目标成为主要利益，（i）通过的位错线的热振动的影响到理论和（ii）参与位错旁路机制。