Ti2AlNb板材应变路径/微观组织耦合热变形材料模型及热成形极限研究

Ti2AlNb alloy is a lightweight high temperature intermetallic, and its complex curved thin-wall integral components have great potential in the field of aerospace and advanced aircraft. In the hot gas forming for Ti2AlNb-alloy complex parts, it is hard to predict the microstructure evolution and forming limit under the complex strain path deformation. Meanwhile, it is inaccurate to describe the materials mechanical behavior under complex stress-strain state by the hot tensile behavior. The complex strain path hot bulging tests and strain path/microstructure coupling materials modeling are adopted to solve the above questions. The biaxial stress-strain curves are realized by the free bulging testing with gas pressure accurate controlling and self-feedback modulating controlling. The high temperature forming limit diagram is tested by the different axial length ratios dies and un-bounded bi-layer bulging test method. The effect of strain path saltation on microstructure evolution of Ti2AlNb sheet is studied by hot bulging test of shape changing dies. Based on the experimental data, the strain path/microstructure coupling unified viscoplastic constitutive equations and VUMAT subroutines are set up, which considers the strain path impact factor. The project can provide a theoretical basis for the application of the high-pressure hot gas forming of Ti2AlNb intermetallic in the application of complex components for aerospace by cooperative of shape and performance.

Ti2AlNb合金为轻质高温金属间化合物，其复杂曲面薄壁整体构件在航空航天领域和尖端飞行器等国防领域具有巨大应用潜力。针对Ti2AlNb高压气胀成形中复杂应变路径变形微观组织预测困难、单向拉伸曲线无法准确描述双向复杂应力应变状态的材料力学行为、高温成形极限图测试及预测难等难题，采用复杂应力路径气胀测试及应变路径/微观组织耦合理论建模等方法开展研究。通过气压精确控制和自反馈微调的自由胀形，实现等双拉应力状态应力应变曲线测试。通过不同的轴长比和覆板胀形，测试板材高温成形极限图。通过形状突变模具胀形实验，研究应变路径突变对Ti2AlNb板材微观组织演变影响。基于实验数据，引入应变路径影响因子，建立应变路径/微观组织耦合的统一粘塑性本构方程及VUMAT子程序。该项目可为Ti2AlNb高温金属间化合物的“控形”-“控性”一体化高压气胀成形工艺在航空航天复杂曲面构件的应用提供理论依据。

针对Ti2AlNb合金和钛合金薄板高温成形“控形-控性”材料模型及高压气胀成形极限测试及预测的目标，开展Ti2AlNb板材和TA32钛合金板材的高温变形及组织演变、应变路径对材料微观组织及材料损伤影响、复杂应变路径构件的微观组织预测、高温成形极限等内容开展研究。已建立了基于物理内变量的统一粘塑性模型、搭建了板材气胀成形及压力控制装置，分析了Ti2AlNb板材高温拉伸行为及组织演变规律，获得了温成形极限图、各向异性变形行为和组织演变规律、钛合金晶体塑性模型等结果，为Ti2AlNb和TA32合金的大型复杂曲面整体结构件热态内高压成形、超塑成形、超塑成形/扩散连接和热冲压工艺成形提供了基础理论。在重要刊物上已发表12篇学术论文，其中SCI论文8篇；申报8项国家发明专利，授权发明专利4项；申报1项实用新型专利，授权1项。培养在读博士研究生2人；培养硕士研究生7人，其中3人已获得硕士学位。