钛/铝复合板非等通道横向共挤压制备工艺及界面结合机制研究

The combination of dissimilar titanium and aluminum alloys enables lightweight, high performance solutions, which is vital for the development of advanced manufacturing technology. However, the major problem with dissimilar titanium-aluminum bonds is emanated from the different properties such as thermal expansion and contraction, leading to the difficulty at various bonding processes. The interface bonding mechanism of titanium-aluminum composite plate by co-extrusion fabrication has not been ensured so far. The purpose of this project is to explore the interrelationship between fabrication technology and microstructural characterization and interface bonding mechanism for dissimilar titanium-aluminum composite plate. First, an innovative fabrication technology is proposed, namely non-equal channel lateral co-extrusion. The experimental set-up with variable angular structures and bearing compensator is developed. Second, the three-dimensional numerical model that couples thermo-mechanical- microstructure multi-physics is established, as well as the demand on a user subroutine of interface microstructural evolution is motivated. The experimental validation of the numerical model is assessed by comparing the extruded deformation and interfacial characterization. Third, to explore the source of tractional distortion during the bimetal co-extrusion, the residual internal stress field and their distribution are analyzed. Then, the optimization of die design and the process control strategy are performed. Fourth, with the help of microscopic characterization, the influences of process paramters of the co-extrusion and heat treatment conditions of the extruded titanium-aluminum composite plate on interface microstructural evolution and underlying bonding mechanics are in depth investigated. Finally, the goals of this project are to identify ways to improve the microstructural and mechanical properties of titanium-aluminum composite plate, and to establish robust process conditions for stable and precise manufacturing of bimetal composite structures.

钛/铝异种合金复合板的制备工艺是轻量化、高性能精密装备技术研究、发展及应用迫切需要解决的关键基础科学问题。本项目从钛、铝合金的热力学性能差异性大以致难复合的特点出发，提出采用非等通道横向共挤压成形连接技术，结合数值模拟仿真和界面微观表征分析，揭示制备工艺—微观组织—界面结合机制三者间的内在联系。首先，构建非等通道横向共挤压制备工艺的物理实验平台；其次，建立热-力-组织多场耦合的三维数值模型，开发界面组织演变计算模块的子程序，并实验验证模型的可靠性；再次，分析共挤压成形的残余内应力和牵引扭曲变形产生的内在关联，提出改进模具设计的优化方案，建立双金属共挤压变形协调控制的工艺优化评价准则；最后，研究共挤压成形工艺和热处理过程对界面微观组织和结合机制的影响规律。本项目研究结果对钛/铝复合板组织性能的可调控性提供科学的指导，对发展高性能和高可靠性的金属复合构件精确塑性成形先进理论和技术具有重要意义。

钛/铝异种合金复合板的制备工艺是轻量化、高性能精密装备技术研究、发展及应用迫切需要解决的关键基础科学问题，尤其在航空零部件。本项目从钛、铝合金的热力学性能差异性大以致难复合的特点出发，提出采用非等通道横向共挤压成形连接技术，结合数值模拟仿真和界面微观表征分析，揭示制备工艺—微观组织—界面结合机制三者间的内在联系。研究了不同挤压比和摩擦接触角模具结构下非等通道横向共挤压成形钛铝复合板的翘曲变形行为及控制策略；研究建立了基于粘弹塑性本构模型的非等通道横向共挤压数值模型，解决了双金属复合边界条件、自适应网格处理等建模关键技术，并分别对非等通道共挤压多场耦合数值模型进行了瞬态和稳态计算分析；研究了钛/铝合金共挤过程中的流动特性，结合微观表征手段分析了不同工艺参数及其耦合作用对钛/铝复合界面形貌和微区力学性能影响的显著性排序，确定了对钛/铝合金界面结合有显著影响的因素，以及共挤过程中界面形貌特征的演变规律；研究了不同热处理工艺条件下复合板材界面附近钛、铝两相显微结构、界面形貌的演变规律。主要研究结果表明：通过正交试验设计和信噪比的分析，“高温低速”的共挤压制备工艺可以作为减小异种双金属共挤压制备过程中产生的翘曲变形缺陷的调控策略。预热温度与平均温度相对偏差呈负相关，挤压速度与平均温度相对偏差呈正相关。工艺参数对挤出力的影响与对平均温度相对偏差的影响相似。热处理温度影响扩散层的生成厚度，580℃时最大扩散层约为1.95μm。520~580℃热处理温度区间内扩散层均有金属间化合物TiAl3生成，同时热处理温度与界面显微硬度成正相关。热处理温度在560℃时最大平均剪切强度达到峰值73.2MPa，复合板界面剪切强度超过了纯铝基材（60MPa）。本项目研究结果对钛/铝复合板组织性能的可调控性提供科学的指导，对发展双金属复合构件精确塑性成形先进理论和技术具有重要意义。