脉冲电流辅助钛合金静轴肩搅拌摩擦焊接头的织构控制研究

Against the problems of uneven heating and poor microstructure-properties performance of friction stir welding joints of titanium alloys with high melting point and low thermal conductivity, this project will use two-phase titanium alloy as the research object, materials characterization and testing will be employed, and research will be carried out on texture control of the joints produced by stationary shoulder friction stir welding with additional pulse current. To perform characterization of texture, integrate the internal morphology of grains and establish the relationship between grain orientation and misorientation and plastic deformation mechanism; the impact mechanism of pulse current on texture will be revealed based on influence of the auxiliary heat source and electrically induced plasticity effect on texture formation of the joint; the orientation relationship between the parent β phase and the daughter αs phase will be analysed through microstructure reconstruction of high temperature parent β phase. Based on relevance between texture and plastic deformation mechanism of the joints, relevance between loading mode of the pulse current and texture of the joints and relevance between the parent phase and the daughter phase of the joints, the formation mechanism of αp phase texture and αs phase texture will be revealed. The type, orientation density and volume fraction of texture will be determined corresponding to the best performance of microstructure-properties of the joints by the quantitative study of texture and the mechanical properties of the joint combined with control of {110} texture of the parent β phase of the joints. The properties of the joints will be verified as influenced by the pulse current through quantitative relationship between the pulse current parameters and mechanical properties. The project will provide theoretical basis for the manufacturing of welded joints with high strength under texture control.

针对具有高熔点、低热导率钛合金搅拌摩擦焊接头受热不均、组织性能差的问题，本项目拟以双相钛合金为研究对象，采用材料表征与测试的方法，研究脉冲电流辅助静轴肩搅拌摩擦焊接头的织构控制。通过接头织构表征，结合晶粒内部形貌，建立接头的晶粒取向和晶粒间取向差与其塑性变形机制的对应关系；通过辅助热源和电致塑性对接头织构形成的影响，揭示脉冲电流对织构的作用机制；通过接头高温β母相的组织重构，建立β母相与αs子相的取向对应关系。基于接头织构与其塑性变形机制、脉冲电流加载方式与接头织构以及接头母相与子相的相关性，揭示接头αp相和αs相织构的形成机理。通过织构与接头力学性能的定量研究，结合对接头β母相{110}织构的控制，确定接头最佳组织性能对应的织构类型、取向密度和体积分数。通过脉冲电流参数与力学性能的定量关系，验证脉冲电流对接头性能的影响。本项目为织构调控下高强度焊接接头的制备奠定理论基础。

针对具有高熔点、低热导率钛合金搅拌摩擦焊接头受热不均、组织性能差的问题，搅拌本项目以双相钛合金为研究对象，采用材料表征与测试的方法，研究脉冲电流辅助静轴搅拌肩搅拌摩擦焊接头的织构控制。通过接头织构表征，结合晶粒内部形貌，建立了接头的搅拌晶粒取向和晶粒间取向差与其塑性变形机制的对应关系；通过辅助热源和电塑性对接搅拌头织构形成的影响，揭示了脉冲电流对织构的作用机制；通过接头高温β母相的组织重构，建立了β母相与αs子相的取向对应关系。基于接头织构与其塑性变形机制、脉冲电流加载方式与接头织构以及接头母相与子相的相关性，揭示了接头αp相织构的形成机理。在脉冲电流作用下，接头的拉伸性能优异。研究了微观组织、织构对接头力学性能的影响规律。通过织构与接头力学性能的对应关系，结合对接头β母相{110}织构的控制，确定接头最佳组织性能对应的织构类型为：随机分布的弱织构。在项目研究中发表标注基金号的论文6篇，其中SCI索引论文6篇。培养和协助指导硕士研究生5人。申请中国发明专利2项，均通过初审。参加国际学术会议2次、国内学术会议5次。通过本项目的研究，探索了钛合金载流静轴肩搅拌摩擦焊接新技术，研究了脉冲电流作用下钛合金静轴肩搅拌摩擦焊接头的织构形成机理，微观组织和织构对接头力学性能的影响规律以及接头的织构控制。在本项目研究成果基础上，拓展了搅拌摩擦焊接工艺，实现了基础理论及前沿技术的拓展与创新。本项目对于织构调控下高强度焊接接头的制备具有重要的学术价值和实际意义。