基于组织控制的Ti2AlNb基合金精密连接内在机制及其接头疲劳行为分析

Focus on the key issues of Ti2AlNb-based alloy applied as a light weight high-temperature structural material in the aerospace field, a novel precision joining technique of Ti2AlNb-based alloy is developed based on microstructure control in this project. The formation mechanism of the joint and microstructure evolution as a result of heat-force conditions are investigated. Moreover, fatigue behavior of the joints both at room and elevated temperatures is studied. The diffusion kinetics equations of Ti-Al-Nb-X multi-system is established to reveal the evolution of B2, O and α2 phase. To obtain a precision joint, the in-situ reaction and surface activation techniques are used to control the interface microstructure during diffusion process. According to the combination of numerical simulation and fatigue tests, the fatigue crack threshold and fatigue crack growth rate of each phase formed in the joints are obtained. In addition, high cycle fatigue properties of joint at room and high temperatures as well as fatigue crack growth mechanism are investigated. Meanwhile, the fatigue failure mechanism of Ti2AlNb-based alloy joint is revealed. By this work, the relationship between precise joining parameters, microstructure control and fatigue failure mechanism of the joints is established, which is beneficial to the application of Ti2AlNb-based alloy in the key components of aerospace engine.

针对新型轻质耐高温结构材料Ti2AlNb基合金在航空航天领域应用的关键问题，本项目开发一种基于组织控制的Ti2AlNb基合金精密连接新技术，深入研究接头形成内在机制，揭示在热-力耦合作用下界面组织的演化规律，阐明接头常温和高温疲劳失效机理。以建立Ti-Al-Nb-X多元体系扩散的动力学方程，明确合金中B2、O、α2相的演化规律为基础，引入原位反应和表面活化技术调控界面组织，实现接头精密成形与控制。采用数值模拟和疲劳实验相结合的方法，获得接头各相的疲劳裂纹扩展门槛值及疲劳裂纹扩展速率，作为界面组织控制依据。考察接头在室温和高温条件下的高周疲劳性能，分析疲劳裂纹的扩展过程，建立接头疲劳失效机制。通过本项目研究，建立精密连接工艺—界面组织演化—接头疲劳失效机制之间的内在关联，提供一种基于组织调控的Ti2AlNb基合金精密连接技术，为Ti2AlNb基合金在发动机关键零部件的应用奠定基础。

本项目针对新型轻质耐高温结构材料Ti2AlNb基合金在航空航天领域应用的关键问题，开发了基于组织控制的Ti2AlNb基合金精密连接新技术。分别设计Ti、Ti/Ni、TiNiNb、B原位增强及Mo颗粒增强中间层，研究了Ti2AlNb基合金接头的连接工艺、界面反应及接头形成过程，重点阐明了生成相之间的晶体学取向及组织变化规律。建立了多元体系扩散的动力学方程，获得Ti在Ti2AlNb基合金中的扩散路径及扩散激活能，建立了扩散层厚度的预测模型。通过高温中子同步衍射技术，深入研究了Ti2AlNb基合金中B2、O相在热循环中的演化规律。明确Ti2AlNb基合金连接时，不同相在接头形成中所起作用。从元素扩散、界面反应、固态相变多个层面系统阐述了不同条件下接头界面强化机制，获得了界面组织精确控制路线。通过纳米压痕、显微硬度、剪切实验、疲劳实验，从相、组织、接头不同尺度分析接头力学性能，建立Ti2AlNb基合金连接接头失效机制。考察接头在室温和高温条件下的服役性能，分析裂纹的扩展过程，揭示了在热-力耦合作用下界面组织的演化规律，阐明了接头常温和高温失效机理。通过本项目研究，建立了精密连接工艺—界面组织演化—接头失效机制之间的关系，提供了基于组织调控的Ti2AlNb基合金精密连接技术，为Ti2AlNb基合金在航空航天关键零部件的应用奠定基础。