共格/非共格纳米相复合强化钢的析出机理和强化机制

Nanoscale precipitation-strengthened steels are promising for many important applications, such as aerospace, transportation, and energy industries, due to their high strength, good weldability, and low material cost. However, these materials tend to suffer from low work-hardening capability and non-uniform deformation, which severely limit their engineering applications. The co-precipitation of coherent and incoherent nanoparticles was found to be one of the effective methods to improve the work-hardening capability and facilitate uniform deformation; nevertheless, the co-precipitation mechanism of coherent/incoherent nanoparticles and its influence on bulk mechanical properties are still unclear at the present time. In this proposed research, we intend to choose the steels strengthened by coherent Cu and incoherent Ni3Ti nanoparticles as the model alloys. The precipitate nanostructural changes, compositional evolution, and interfacial segregation behavior of Cu and Ni3Ti nanoparticles will be investigated through a combination of 3D atom probe tomography, transmission electronic microscopy, first-principles calculations, and mechanical tests. Emphasis will be placed on the understanding of the nucleation, growth, and coarsening of the coherent and incoherent nanoparticles, aiming at elucidating the nanoscale co-precipitation mechanism. In addition, based on the study of the correlation between precipitate microstructure and material mechanical properties, the underlying strengthening mechanism will be revealed. This proposed research will not only shed new insights on the understanding of nanoscale co-precipitation mechanism but also provide useful guidelines for optimizing mechanical properties of nanoscale precipitation-strengthened steels.

纳米析出强化钢具有高强度、良好焊接性能和较低成本的优势，在航空航天、交通运输和新能源等战略领域有极大的应用潜力，但加工硬化能力不足、均匀变形能力差是制约其工程应用的瓶颈问题。共格和非共格纳米相复合析出是一种提高纳米析出强化钢加工硬化和均匀变形能力的重要方法，但目前对共格/非共格纳米相的复合析出机理和强化机制尚不完全清楚。本项目拟以共格Cu和非共格Ni3Ti纳米相复合强化钢为模型合金，利用三维原子探针、透射电镜、第一性原理计算和力学性能测试等方法研究Cu和Ni3Ti纳米相的组织形貌变化、成分演化和界面偏析行为，分析Cu和Ni3Ti纳米相的形核、长大和粗化规律，阐明Cu和Ni3Ti纳米相复合析出的机理，建立纳米析出组织和材料力学性能的关联，揭示共格/非共格纳米相的复合强化机制。本项目的开展有利于加深对共格/非共格纳米相复合析出机理的理解，并为进一步优化纳米析出强化钢的综合力学性能提供理论依据。

纳米析出强化钢具有高强度、良好焊接性能和较低成本的优势，在航空航天、交通运输和新能源等战略领域有极大的应用潜力，但加工硬化能力不足、均匀变形能力差是制约其工程应用的瓶颈问题。本项目以共格/非共格纳米相复合强化钢为模型，以深入理解纳米相复合析出机理、粗化规律和强化机制为基础，开发了一系列具有优良强韧性的新型纳米复合析出强化钢，系统研究了纳米复合析出强化钢微观组织和力学性能的关联等问题。具体工作包括：1）开发了具有超高强度和良好塑性的新型纳米复合析出强化钢；2）从热力学和动力学角度系统分析了Cu和Ni3Ti复合纳米相的形核和长大过程，阐明了共格/非共格纳米相复合析出的机理；3）系统研究了共格/非共格纳米相的粗化行为，揭示了共格/非共格纳米相的粗化规律；4）建立了纳米复合析出微观组织和高强钢力学性能的关联，揭示了共格/非共格纳米相复合强化钢的强化机理。在以上研究成果的基础上，本项目发表SCI论文5篇，其中Acta Materialia 2篇，申请发明专利1项，培养博士生2人。