周期性钛合金层和晶化控制强韧化Ti2AlC/TiAl基合金的耦合作用机理

How to effectively solve the dilemma between strength and plasticity/stiffness of TiAl-based alloys, and realize simultaneous increasing of the strength and plasticity/stiffness, is the key to broaden their applications in the field of high technology. Inspired by the nacre with multi-scale and hierarchical structures, via biomimetic structure design is an effective approach to improve the properties of the structural materials. In our project, based on the composite strengthening technology and biomimetic structure design concept, we select Ti2AlC as the reinforcements and titanium alloy foils (Ti-6Al-4V) as the toughening layers, firstly overlay and cold-press the Ti3AlC2/Ti-Al amorphous powders and titanium alloy foils, and then fabricate by Spark Plasma Sintering (SPS) technology to achieve the Ti2AlC/TiAl-based alloys sheets toughened by cyclical titanium alloy layers, finally by means of the thermal deformation technology to increase interlamellar binding force and optimize the texture of the materials. The effect of preparation process parameters of the Ti3AlC2/Ti-Al amorphous powders on the sintering performance and crystallization behavior of Ti2AlC/TiAl-based alloys is investigated. The influence of forming technology of the composite sheets on the interface characteristic, multi-laminated structures, microstructure evolution, and the development rule of the defect is analyzed. By optimizing the process parameters, we can achieve the combination rules and controlling technology of the multilayers. By establishing the relationship of process, composite multi-laminated structures and room-temperature or high-temperature performance, the room-temperature fracture behavior and high-temperature plastic deformation behavior or characteristic are analyzed. Thereby, the coupling mechanism of the multi-laminated structures and Ti2AlC reinforcements are revealed. Our researches provide new idea and theoretical foundation for developing TiAl-based alloys with high strength and toughness, multi-scale and hierarchical structures, which can satisfy the urgent needs for high-performance sheets in the industries of aeronautics and astronautics, military and automobile.

如何有效平衡TiAl基合金强度和韧塑性之间的矛盾，实现强度和韧塑性协同提高是拓宽其应用的关键。受贝壳多尺度结构的启发，通过仿生结构设计成为提高性能的有效途径。本项目基于复合化技术和仿生结构设计理念，将Ti3AlC2/Ti-Al非晶粉末和钛合金箔逐层叠加冷压成型，采用放电等离子烧结技术制备周期性钛合金层增强Ti2AlC/TiAl基合金，通过热变形技术提高层间结合力和优化织构。分析非晶粉末制备参数对Ti2AlC/TiAl基合金烧结性能和晶化行为的影响。研究板材成形工艺对界面、叠层结构及组织结构演变和缺陷形成与演化规律的影响，通过优化工艺，获得叠层间的结合规律与控制技术。构建工艺、结构和室温及高温性能间的关系，分析断裂和塑性变形行为及特征，揭示叠层结构和Ti2AlC相的耦合作用机理。为发展高强韧仿生结构TiAl基合金提供新的思路和理论基础，满足航空航天、国防及汽车工业等对高性能板材的迫切需求。

发展以结构为首要因素的构型化复合设计理念，是突破传统金属基复合材料强韧性失配瓶颈的有效途径。本课题通过创新构型及优选MAX陶瓷相，采用放电等离子烧结技术（SPS）成功制备了多尺度周期性TC4钛合金层增强Ti2AlC/TiAl基合金，分析了工艺设计对界面结合及叠层结构的影响规律，揭示了叠层结构和Ti2AlC相的耦合作用机理，抗弯强度最大达1428.79MPa，断裂韧性最大达64.08MPa·m1/2。通过断裂特征及裂纹扩展模式分析发现，叠层结构设计具有独特的能量耗散和几何约束效应，裂纹由复合层扩展到强韧层时会出现明显的偏转、分叉等削弱裂纹扩展驱动力的行为，裂纹尖端明显钝化，裂纹扩展受阻。且随着强韧层层数的增加，裂纹扩展距离缩短，分叉时分叉角逐渐增大，裂纹尖端应力进一步削弱，从而大大消耗了裂纹扩展驱动力；第二相Ti2AlC的存在发挥了颗粒钉扎强化作用。为设计和发展高强韧、多尺度复合结构TiAl基合金提供实验指导。. 对TC4钛合金箔特殊加工处理，尝试开发了“砖砌式”叠层结构TC4钛合金层和MAX相协同强韧化TiAl基合金，揭示了特殊结构和力学行为之间的构效关系，发现“砖-泥-桥”仿生结构由于层状结构的韧化和三维连通的金属基体，更好地发挥了构型调控作用，为新型仿生TiAl基合金的后续研究奠定基础。