薄壁铝合金管材缩口热挤压增厚变形行为及组织与性能研究

管材塑性加工是先进塑性加工技术研究与发展的一个重要方向。目前飞机拉杆类零件采用管材缩口成形后铆接螺纹套筒方法制造，连接强度不稳定、制造成本较高。若采用新方法将管材缩口处径向增厚后直接攻螺纹，则将显著增加飞机拉杆的连接强度与降低成本。为此，本项目开展薄壁铝合金管材缩口热挤压增厚变形行为及组织与性能研究。管材与其母材棒料或板料性能不同，而管热挤压与其弯曲、胀形受力状态不同，因此本项目首先需建立管材在热压下性能测试的方法，从而构建管材热压下的可靠本构模型；其次，采用数值模拟，研究管材缩口热挤压受力状态与材料流变行为；在此基础上，设计管缩口热挤压加热装置与模具，开展薄壁铝合金管材缩口热挤压增厚实验研究；并探索成形路径、挤压温度、挤压速度、润滑条件等对缩口增厚处组织与性能的影响规律与控制方法。从而最终建立管材缩口热挤压增厚的新方法、新理论，并为该技术在飞机工业中的应用奠定坚实的理论基础。

Tube plastic forming has been an important research and development direction in advanced plastic process technology. Currently, the kind of pull-rod parts in aircraft are fabricated with the method of tube necking and riveting threaded sleeve. The connection strength of pull-rods are instable and their manufacturing costs are high. If the necking of pull-rod parts are used in a new method to thicken the tube wall and attack thread, the method will significantly increase the strength of connection and reduce the cost of the aircraft. So the deformation behavior and microstructure and properties in the thickening process of the necking and hot extrusion of thin-walled aluminum tube is studied in the project. The properties of tube, bar and plate of the same material is different. And the hot extrusion of tube is different from its bending and bulging in stress state. So the tube hot performance test method firstly need to be established and then build the reliable constitutive model of tube. Secondly, the numerical simulations of tube necking and hot extrusion will be used to analyse the strss state and the rheological behavior of the material. On this basis, the heating equipment and die will be designed and the experiment of the tube necking and hot extrusion will becarried on. The influence of forming path, extrusion temperature, extrusion speed, lubrication conditions on the microstructure and properties of the thickening of tube necking and the control method of its microstructure and properties will be explored. Ultimately, a new method and new theory on the thickening of tube necking and hot extrusion will be established and lay a solid theoretical foundation for application of the technology in the aircraft industry.