高熵合金原子层次异质结构强韧化机理研究

异质结构是高熵合金的重要强韧化方式之一，可以提升其强度，甚至实现强度和塑性的同步提升。具有强韧化效果异质结构的尺寸介于几个纳米~几十个纳米，虽然通过高角环形暗场像或原子层次成分分析技术，已可以表征静态条件下异质结构的原子层次显微结构，但由于缺乏原子层次的力学实验方法，导致异质结构原子层次强韧化机理不清晰。本申请拟采用申请人作为技术骨干研制的原子层次原位TEM力学研究系统，结合离位TEM分析方法，系统研究异质结构的尺寸、结构和分布影响位错形核和运动的规律；此基础上，调控合金组分、凝固/热处理工艺对异质结构进行优化，验证异质结构的强韧化机理，建立成分/工艺—异质结构—原子层次强韧化机理—力学性能的关联关系，为高熵合金的设计提供实验和理论依据。申请人已进行前期的工作积累，制备出含不同异质结构的高熵合金，对其力学性能和显微结构进行了表征，相比于均质高熵合金，异质结构同步提升了合金的强度和塑性。

Heterostructure is one of the important toughening mechanisms of high entropy alloys, which can increase its strength, and even achieve simultaneous improvement of strength and plasticity. The size of the heterostructure with strong toughening effect ranges from a few nanometers to tens of nanometers. Although the atomic scale microstructure of the heterostructure under static conditions can be characterized by high-angle annular dark field image and atomic scale composition analysis technology, however, the toughening mechanism of heterostructure still remain unknown, because of the lack of atomic scale mechanical testing methods. This application intends to use the atomic level in-situ TEM mechanical testing system, developed by the applicant as the technical backbone, combined with the ex-situ TEM analysis, to systematically study the atomic scale toughening mechanism. This application intends to systematically study the influence of the size, structure and distribution of heterostructures on the dislocation nucleation and motion. Base on the above results, the heterostructure will be optimized by adjusting the alloy composition and solidification/heat treatment process, to further verify the toughening mechanism of the heterostructure. This application intends to establish correlations of the composition/process—heterostructure—atomic scale toughening mechanism—mechanical properties and provide experimental and theoretical basis for further design of high entropy alloys. Some preliminary experiments have been conducted, including preparation of high entropy alloys with different heterostructures, characterization of their mechanical properties and microstructures. Compared with the homogeneous high entropy alloys, heterostructures has been proven to simultaneously improved the alloy's strength and plasticity.