| 单晶铜塑性变形的二维离散位错动力学模拟研究 |
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| 作者姓名： | 王春晖 孙朝阳 郭祥如 魏云灿 蔡旺 |
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| 作者单位： | 1.北京科技大学机械工程学院, 北京 100083 |
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| 基金项目： | 国家自然科学基金委员会与英国皇家学会合作交流资助项目（51911530209）；国家自然科学基金面上资助项目（52175285）；国家自然科学基金NSAF联合资助项目（U1730121）；北京科技大学顺德研究生院科技创新专项基金资助项目（BK19CE008） |
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| 摘 要： | 针对亚微米尺度晶体元器件在加工和服役中出现的反常力学行为和动态变形等问题，基于离散位错动力学理论建立了单晶铜塑性变形过程的二维离散位错动力学模型。该模型考虑外加载荷、位错间相互力和自由表面镜像力对位错的作用机制，引入了截断位错速度准则。与微压缩实验对比验证了模型的正确性，并且能够描述力加载描述的位错雪崩现象。应用该模型分析了不同加载方式和应变率下位错演化及力学行为，结果表明:当外部约束为力加载和位移加载时，应力应变曲线分别呈现出台阶状的应变突增和锯齿状的应力陡降，位错雪崩效应的内在机制则分别归结为位错速度的随机性和位错源开动的间歇性；应变率在102～4×104 s?1范围内，单晶铜屈服应力的应变率敏感性发生改变，位错演化特征由单滑移转变为多滑移面激活的均匀变形，位错增殖逐渐代替位错源激活作为流动应力的主导机制。
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| 关 键 词： | 单晶铜 离散位错动力学 加载方式 应变率 力学行为 |
| 收稿时间： | 2021-04-21 |
Investigation of the plastic deformation of single crystal copper using a two-dimensional discrete dislocation dynamics model |
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| Authors: | WANG Chun-hui SUN Chao-yang GUO Xiang-ru WEI Yun-can CAI Wang |
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| Affiliation: | 1.School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China2.Beijing Key Laboratory of Lightweight Metal Forming, University of Science and Technology Beijing, Beijing 100083, China3.Shunde Graduate School, University of Science and Technology Beijing, Foshan 528000, China4.Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, School of Mechanical Engineering, Tianjin University of Technology, Tianjin 300384, China |
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| Abstract: | Microelectromechanical systems (MEMS) that feature components with the same geometrical size as that of an individual grain have been widely used in a variety of industries, including electronics, machinery, energy, transportation, aerospace, and architecture. Owing to the widespread engineering application of MEMS and nanoelectromechanical system devices, including sensors and actuators, submicron scale crystal materials exhibit mechanical behaviors different from those of macroscale materials, such as size effect, intermittent plastic flow, and strain rate effect, that have become significant topics in mechanics and materials research in recent years. Since dislocations are the carriers of plastic deformation, understanding the dislocation mechanism of submicron crystalline materials is crucial for designing and predicting microdevice reliability. To improve the understanding of abnormal mechanical behavior and dynamic deformation of submicron scale crystal components in processing and application, a two-dimensional discrete dislocation dynamics model of single crystal copper for plastic deformation was established based on the discrete dislocation dynamics theory. The effects of applied load, dislocation interactions, and image force by the free surface on dislocations were all considered in the numerical model, and the cutoff weighted dislocation velocity was also introduced. The model can be used to describe the “dislocation avalanche” effect under stress-controlled modes and interpret the dislocation evolution and mechanical behavior under different loading modes and strain rates, as demonstrated by microcompression experiments. When the external loading modes are force control and displacement control, the stress–strain curves show a step-like character under strain and a sharply serrated character under stress, respectively. The randomization of the dislocation velocity and intermittent activation of dislocation sources are the internal mechanisms of the dislocation avalanche effect. The strain rate sensitivity of the yield stress for single crystal copper changes in the strain rate range of 102–4 × 104 s?1. The evolution characteristics of the dislocations change from single slip plane to uniform deformations induced by multiple slip planes activation, and the dominant mechanism for the strain rate effect of yield stress is dislocation multiplication rather than dislocation source activation. |
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