新型TiAl-钛合金层状复合板材高温轧制变形行为及强韧化机理

As high-performance structural materials, light weight and high-temperature resistant TiAl alloy sheets are much-needed for the aerospace industry. However, both difficult to roll forming and the inverse relationship between tensile properties and fracture toughness of TiAl alloy sheets have hampered their application. In the present project, a hot rolling processing method of the metal-intermetallic laminate composite sheets, concerning preparation of TiAl-Ti alloy laminate composite sheets with one layer or more layers TiAl, was put forward. Both formability and balanced mechanical properties of the laminate composite sheets are more excellent than that of TiAl alloy sheets. At present, very few experimental and theoretical studies, such as hot rolling deformation behavior, interface evolution and reinforcing and toughening mechanisms of the laminate composite sheets, have been reported in the field of metal-intermetallic laminate composites. After the completion of the project, we hope that some mechanisms, such as both the formation kinetics and thermal stability of interfacial microstructure, the coordination deformation mechanism between Ti alloy and TiAl, the reinforcing and toughening mechanisms, the fracture mechanism, the coupling law of microstructure and macroscopic mechanical behavior and the evolution of microstructure and mechanical properties of the laminate composite sheets after different heat treatments, can be revealed. Moreover, we also hope that the models, such as the interfacial micro-region evolution under the interaction between deformation and phase transformation and the relationship among preparation technology, microstructures and mechanical properties, can be constructed, which is useful for us to understand the correlation between microstructures and macroscopic mechanical properties and achieve the controls both the shape and the mechanical properties of the TiAl-Ti alloy laminate composite sheets. The relative experimental and theoretical research results of the project will promote the development and the application in the aerospace industry of large-size, high-quality TiAl-Ti alloy laminated composite sheets.

轻质、耐热TiAl合金板材是航空、航天工业急需的高性能结构材料，但TiAl合金板材由于具有轧制成形困难、室温拉伸性能与断裂韧性具有反常关系等特点，阻碍了板材的应用。通过热轧制备TiAl-钛合金层状复合板材可显著改善板材的成形性和综合力学性能。但关于这种复合板材的高温轧制变形行为、界面演化及强韧化机理还鲜有报道。通过本课题的研究，揭示TiAl-钛合金层状复合板材的界面微结构形成的动力学规律及稳定性、协调变形机制、强韧化机理、断裂机制、微观组织结构与宏观力学行为的耦合规律、不同热处理条件下复合板材的组织性能变化规律，建立形变与相变交互作用下的界面微区演变模型、板材制备-微观组织结构-力学性能的关系模型，近一步理解复合板材的微观特性与宏观性能的相关性，实现对复合板材控形与控性，为促进大尺寸、高质量TiAl-钛合金层状复合板材的研制及其在航天、航空等领域的应用奠定理论基础。

TiAl合金以其低密度、高比强度、优异的高温抗氧化性等特点，在航空航天领域具有重要的应用潜力。但较低位错可动性以及较少的滑移系和孪晶系导致其室温脆性大，这严重阻碍了TiAl合金的应用。本课题针对TiAl合金的缺点，采用包套热轧等技术制备了TiAl-钛合金叠层复合板材，并阐明了复合板材界面演化及界面微区性能，揭示了复合板材的强韧化机理，获得了热处理对复合板材组织性能的影响规律，建立了相关模型。制备的TiAl-钛合金层状复合板材，显著地改善了TiAl合金的脆性问题，断裂韧性明显提高，最高断裂韧性达到TiAl合金的1倍以上（35MPa•m1/2），这为TiAl合金在航空、航天领域的应用奠定了理论与技术基础。另外，TiAl-钛合金层状复合板材的动态压缩性能远高于文献中报道的Ti6Al4V-Al3Ti层状复合材料和Ti6Al4V合金的数据，其中最高动态压缩强度是文献中的近一倍（2547MPa），而压缩应变和冲击吸收能远超Ti6Al4V-Al3Ti层状复合材料（最高达到0.33和530MJ•m-3），展现出非常优异的动态压缩性能，在防弹装甲领域显示出巨大的应用潜力。