面心立方金属材料压入初期突变现象的位错机制

接触应力是引发金属构件形变与失效的重要来源之一。为了理解材料的力学行为与失效机制,研究者对接触条件下位错的产生与运动开展了大量研究。然而由于实验技术的限制,对接触初期塑性变形机理的认识仍较为薄弱。近年来得益于原位表征和高测试精度的优点,仪器化纳米压入技术被陆续地应用于研究材料接触初期变形行为,尤其针对面心立方结构(FCC)的金属材料,结合模拟分析与微观表征,大大促进了对相关位错行为的理解。因此,在简要介绍仪器化纳米压入技术的特点、模型及应用的基础之上,首先,介绍了纳米压入接触初期载荷-位移曲线的突变现象,讨论了其与位错行为的关系;其次,重点以面心立方金属材料为对象,从位错萌生和位错运动与反应两个方面分别介绍了二者与突变现象的关系,并结合文献报道,详细讨论了压入过程位错萌生的影响因素,以及位错运动与反应机制;最后,进行了总结和展望,提出借助多种先进实验和模拟方法的交叉使用,将有助于揭示接触条件下的位错行为,从而为仪器化纳米压入技术的发展和理解接触条件下金属材料的变形与失效提供理论基础。

Dislocation Mechanism of Discontinuous Phenomenon in Incipient Stage of Face-centered Cubic Metal Indentation

Contact stress is one of the main sources causing deformation and failure of metallic engineering components. In order to investigate the mechanical behavior and failure mechanism of materials, many studies have been carried out to explore the nucleation and motion of dislocation under contact condition. Unfortunately, the knowledge of incipient plasticity are still unclear due to the limitation of testing technologies. With the advantages of in-situ characterization and high resolution, instrumental nanoindentation has been increasingly used to study incipient plasticity in recent years, especially for face-centered cubic metals, which further boosts the understanding of the dislocation behavior by combining simulation and advanced characterization methods. Therefore, based on the brief introduction of the characteristics, analysis model and applications of instrumental nanoindentation, the discontinuities of load-displacement curve were introduced and the relationship with dislocation behavior was discussed. Secondly, focusing on face-centered cubic metal materials, the relationship between dislocation initiation and dislocation motion and reaction and discontinuities were illustrated respectively. Based on literature review, the influencing factors of nucleation and the mechanism of motion and reaction were discussed in details. Finally, conclusion and prospect were put forward. Multiple application of advanced experimental and modelling methods will benefit the disclosure of dislocation behavior under contact, thus providing the theoretic basis for the development of instrumental nanoindentaion and understanding of deformation and failure of metallic materials under contact.