具有复杂大厚差特征的高强铝合金零件热辅助浮动镦锻成形工艺与机理研究

The rational use of light-weight material and light body structure is an effective way to realize the energy saving and emission reduction requirements of vehicles such as aircraft and automobile. Based on this idea, the research on heat-assisted floating upsetting-forging process and its mechanism for complex and large thickness variation component by high-strength Al-alloy plate will be carried out in this project. Through the establishment of material flow model for high strength Al-alloy plate in large deformation and the microstructure evolution model during the thermo-forming process, under the condition of non-uniform temperature and local floating forming, the thermo-mechanical and microstructure coupling simulation can be realized; combined with the construction of experiment platform for heat-assisted floating upsetting-forging process, the data basis for the research on heat-assisted sheet bulk forming will be provided. The material flow law during the plate forging of components with large thickness variation under the condition of non-uniform temperature field and complex loading will be revealed, and the process window of the heat-assisted floating upsetting-forging process for high strength Al-alloy will be established, which lays the theoretical and technological foundation of the light-weight design and manufacturing. The evolution law of the microstructure during dynamic recovery, recrystallization and texture transformation of high strength Al-alloy in the floating forming zone under complex boundary conditions will be analyzed, and the internal relationship among the heat-assisted floating upsetting-forging process, heat transfer and microstructure evolution will be clarified, so as to realize the coordinated control of forming process, microstructure and performance-in-service, which will be the scientific basis for the integration of shape forming and property achievement.

轻质材料与轻体结构的合理运用，是飞机、汽车等运载工具实现节能减排要求的有效途径。基于这一理念，本项目拟开展面向具有复杂大厚差特征的高强铝合金零件热辅助浮动镦锻成形工艺与机理研究。通过建立非均匀温度与局部浮动变形条件下，高强铝合金板料大变形流动应力模型和热成形过程微观组织演变模型，实现热-力-组织多场耦合仿真；结合热辅助浮动镦锻成形实验平台的构建，为热辅助板料体积成形研究提供数据基础。揭示非均匀温度场与复杂加载作用下，大厚差零件板料锻造过程中的材料流动规律，建立高强铝合金热辅助浮动镦锻成形工艺窗口，为轻量化结构设计与制造奠定理论和技术基础。分析浮动变形区内复杂边界条件下，高强铝合金动态回复与再结晶以及织构转变等微观组织的演变规律，明确热辅助浮动镦锻成形-传热-微观组织演变之间的内在联系，实现成形工艺、微观组织与零件服役性能的协调控制，为成形/成性一体化调控提供科学依据。

航空、汽车工业中的许多零部件，已呈现出结构复杂、材料轻质高强及壁厚差异大等特点。板料体积成形是一种先进塑性成形工艺，以板材为坯料，利用模具和工艺设计来控制材料流动，实现复杂非等厚特征的成形制造。然而，板料体积成形工艺在实施板料面内压缩时，易产生失稳起皱和折叠缺陷。本项目旨在采用热辅助方法改善浮动镦锻成形过程中材料流动性，通过物理实验、多场跨尺度集成计算及微观组织表征分析相结合的方法，实现具有大厚差特征的高强铝合金齿形零件的成形制造。.项目提出了一种通过协调工件、模具工作元件之间的相对运动模式，使侧壁材料在成形过程中从保持型腔逐渐挤入成形型腔，利用稳定塑性变形区完成成形的方式，解决了传统侧壁镦锻存在的轴向失稳、成形极限受限以及载荷激增的三大难题。.围绕材料流动控制目标，建立了反顶力理论计算模型；利用锥角凹模构成倾斜的预留型腔，可抑制材料的成形失稳；定量分析不同结构参数的模具表面微特征对材料流动的影响规律，明确模具微特征的增摩或减摩效果取决于材料流动阻力和润滑剂储存能力的共同作用；以增厚比和反顶力为约束，建立了可控变形区镦锻成形工艺窗口。.项目以固溶温度、固溶时间及应变速率为变量，研究了W态7075铝合金的热变形行为和组织演变规律，建立了统一粘塑性本构模型，并基于遗传算法对所建立的模型参数进行求解优化。搭建了一套集成化测量装置，对导热系数、对流换热系数和接触导热系数进行精准可靠的测定，误差控制在4%以内。完成了接触导热系数关于接触温度和接触应力的多变量映射关系，获得了适用于全域的接触导热系数。.项目以高强铝合金齿形件为工艺落脚点，设计了固溶处理-热辅助浮动镦锻成形-人工时效的工艺路线。通过开展多尺度集成计算，研究了成形温度、成形速度和反顶力对零件成形质量的影响。微观组织观察结果表明，热成形后变形区材料发生了明显的再结晶，形成细小晶粒，经人工时效处理后的齿面硬度可达到92%的T6态硬度值。