轻合金管状构件热态颗粒介质压力成形工艺及理论研究

Hot granules medium pressure forming process uses heat-resistant granules medium instead of liquid or gas in the internal high pressure thermoforming process to form lightweight alloy tubes. As granules medium is easy to seal, pressure is easy to establish, distribution of internal pressure is non-uniform, the friction between the sheet and granules medium is helpful for the forming of sheet, the process not only keeps the traditional advantages of high pressure thermoforming process, but also its forming temperature range is wider, do not need special sealing device and external pressurization system, so this process can provide a more accurate, convenient and economical method for thermoforming of lightweight alloy tubes that with thin-wall, large-diameter, complex cross-section. In order to figure out the process features and mechanism, many studies would be carried out: (1) establish heat constitutive equations, yield criteria and pressure transmission model of granules medium, accurately descript the macro-mechanical characteristics of granules medium under high-temperature and high-pressure. (2) establish a coupling simulation model of discrete element and finite element, accurately analysis coupling plastic deformation of discrete particles medium and continuous tube. (3) establish hot particle pressure forming technology theory and process specifications. This project is the extension of the internal high pressure thermoforming technology, it will promote the applications of lightweight alloy tubes in aviation, aerospace and military industry and other high-tech field.

热颗粒介质压力成形新工艺是采用耐热颗粒介质代替现有内高压热成形工艺中液体或气体的作用，实现轻合金管状构件成形。发挥耐热颗粒介质易于密封、压力建立简便、内压非均匀分布、与坯料接触产生有益摩擦作用等特殊性能，使该工艺既传承了现有内高压热成形技术的优点，又具有成形温度区间更宽、无需特殊密封装置、无需外部增压系统等优势，以期为解决薄壁、大口径、复杂截面的轻合金管状构件热成形难题提供更精确、更便捷、更经济的新方法。为探明工艺特征和机理，本项目拟开展以下研究：(1)构建颗粒介质热态本构方程、流动准则及传压力学模型，准确描述颗粒介质在高温、高压条件下的宏观力学特征；(2)构建离散元与有限元分体耦合仿真模型，精确分析离散体颗粒介质与连续体管件耦合塑性变形问题；(3)建立热颗粒介质压力成形技术理论和工艺规范。本项目研究是内高压热成形技术的拓展，将进一步促进轻合金管状构件在航空、航天和军工等高技术领域的应用。

热颗粒介质压力成形技术是管状构件内高压成形技术的拓展，采用耐热颗粒介质代替现有内高压热成形工艺中液体或气体的作用，实现轻合金管状构件成形。本项目建立了颗粒簇物质在高温高压条件下的热态本构方程和传压力学模型，并分别采用有限元和离散元法对传压性能进行了数值仿真和试验验证，得到了不同变形条件下颗粒介质的建模参数，准确描述了颗粒介质的宏观力学特征。以AA5083铝合金卷焊管和AA6061铝合金挤压管为研究对象，通过材料拉伸试验和组织金相观测，研究合金热态变形特征和热处理条件对材料性能的影响，建立考虑厚向应力影响的铝合金薄壳理论成形极限图，分析了在厚向应力诱导下的材料性能参数对理论FLD的影响规律。针对热态颗粒介质压力成形工艺中颗粒介质与管材耦合变形的特征，建立离散元与有限元分体耦合仿真模型，准确分析了成形过程中具有离散特征的颗粒介质和连续塑性变形特征的合金管材的承载和变形过程，为解决具有离散特征材料与塑性变形特征材料耦合作用的力学问题提供新的分析方法，拓展了数值仿真方法的应用范围。提出了热态颗粒介质压力成形(HGMF)新工艺，基于压力非均匀分布，以及颗粒介质与管坯接触摩擦作用等工艺特征，建立了管件自由胀形和角部贴膜力学解析模型，解析得到了管件自由胀形和角部贴合等主要变形过程的特征参数。建立了基于Drucker-Prager线性材料模型假设的管件HGMF工艺仿真模型，分析了不同加载路径和工艺参数对成形性能的影响，确定了AA5083卷焊管等温成形工艺方案，成功制备了典型Ω形凸环管件。提出了可热处理强化铝合金构件“固溶处理+颗粒介质内高压成形+人工时效”成形工艺方案，成功试制了AA6061挤压管材质的阶梯轴、六棱轴等典型管件。结合以上研究，发表论文10篇，申请发明专利1项，另录用5篇论文。培养博士研究生2名，硕士研究生4名。该项目成果已在航天领域管件制造中得到了初步应用，目前正积极向冶金和化工领域的钢铝复合管件方向拓展。