Ti2AlNb基合金组织演变特征及其对损伤容限性能的影响

Based on plastic deformation characteristics of Ti2AlNb-based alloy, and on the control target of microstructure, processability and of damage tolerance properties, through the prediction and control of characteristics of microstructural evolution and of principles of defects formation and evolution, by using a method of combination of a modified dynamic material model and numerical simulation and physical simulation, the microstructural characteristics and plastic deformation mechanism under different deformation conditions are obtained. The formation and evolution mechanism of defects and microstructure under coupled multi-field condition is disclosed. And the thermodynamics model and the kinetics model are also constructed for describing microstructure evolution and defect formation. The damage tolerance behavior of the Ti2AlNb-based alloy is systematically studied and evaluated by using a combined method of macroscopic experiment and microcosmic analysis. The influence of different deformed microstructure on damage tolerance properties is analyzed. And the quantitative models of fracture toughness, crack growth rate and the threshold value of crack propagation were established. On the base of the above, the qualitative relationship and quantitative relationship among deformation parameters of the Ti2AlNb-based alloy, efficiency of power dissipation, microstructure characteristics and defect, damage tolerance properties will be obtained. This can realize the integration of properties design and process design. The research results can provide the theoretical basis of the precise formation of complex components based on Ti2AlNb-based alloy, and of the precise control of microstructure and damage tolerance properties.

根据Ti2AlNb基合金的成形特点，以微观组织、可加工性能及损伤容限性能为控制目标，采用修正的动态材料模型、极性交互模型、数值模拟并结合物理模拟的方法对微观组织演变特征和缺陷形成及变化规律进行预测和控制，掌握不同变形条件下的塑性变形机制；揭示多场耦合作用下组织及缺陷的形成和变化规律，并构建组织演变和缺陷形成的热力学和动力学模型。采用宏观试验和微观分析相结合的办法，系统研究Ti2AlNb基合金的损伤容限性能，分析不同微观组织对损伤容限性能的影响规律，建立断裂韧性、裂纹扩展速率及裂纹扩展门槛值的定量模型，最终确定出变形工艺参数-功率耗散效率-微观组织（含缺陷）-损伤容限性能之间的定性和定量关系，获得优化的变形工艺参数范围，实现性能设计与工艺设计的一体化。研究结果可为Ti2AlNb基合金复杂构件精确成形及微观组织和损伤容限性能的精确控制提供理论基础。

Ti2AlNb 基合金除具有较高的比强度、比刚度外，还具有高温强度高、抗氧化性能好、抗蠕变性能优良及热膨胀系数低等特点，是新型航空发动机首选的关键材料之一。项目根据Ti2AlNb基合金的成形特点，以成形件的组织和性能为控制目标，综合采用动态材料模型、极性交互模型、数值模拟并结合物理模拟的方法，对该合金的成形过程进行了分析。研究了变形及热处理工艺制度优化及其组织、缺陷形成及控制技术，掌握了不同工艺制度对Ti2AlNb基合金微观组织和性能的影响规律。在等温恒应变速率压缩实验的基础上，构建了不同成分Ti2AlNb基合金的本构关系模型，分析了变形工艺参数对其微观组织（含缺陷）的影响规律。根据动态材料模型和极性交互模型，计算相关能量参数，采用不同稳定或失稳准则构建出Ti2AlNb基合金在不同应变下的加工图，并对加工图中不同区域变形试样的微观组织进行分析，确定出各区域的组织演变特征、变形机理和损伤机制。并基于Deform软件平台进行二次开发，进一步分析了Ti2AlNb基合金典型构件不同部位形状尺寸变化和微观组织（含缺陷）演变规律，掌握了该合金的塑性变形机理及其对性能的影响，最终得到优化的变形工艺参数范围。研究结果可为Ti2AlNb基合金复杂构件精确成形和微观组织的精确控制提供理论基础。