铝合金挤压铸造扭转复合成形组织演变机理及形性协同控制研究

The aluminum rotary parts are the critical lightweight components in the equipment for the aerospace and national defense weapons. However it is difficult to simultaneously achieve both processing efficiency and mechanical properties by the present casting and plastic forming processing. In the present project, it is proposed that the torsion shear deformation is introduced into the squeeze casting. Employing experiments and multi-scale simulation, the microstructural evolution and shape/performance control method are discussed: 1) The physical and mechanical properties is analyzed during the squeeze casting-torsion complex forming (SCTCF). The consecutive equation for aluminum alloy during high temperature and the interfacial heat transfer coefficient and friction behavior during forming process are investigated. Then, the finite element model is established. Finally, the coupled thermo-mechanical mechanism of SCTCF is ascertained. 2) The microstructural structure and mechanical properties are studied. The grain breakage, refinement and rotation under temperature-pressure-torsion shear complex loading are investigated. Then, the effects of the workpiece size and technical parameters on the microstructure and mechanical properties are confirmed. 3) The micromechanical model for grain breakage and refinement is established and coupled with finite element and visco-plastic self-consistent (VPSC) to establish the macro and micro deformation prediction method. Then, the microstructural evolution mechanism is revealed. Finally, the technical parameters and deformation processing are optimized. Microstructure and mechanical properties are controlled and the technical prototype is established. The implementation of this project is of great significance for discovering the forming theory and control method of most effective production of the high-performance aluminum alloy.

铝合金回转件是航空航天及武器等装备中关键的轻量化部件，但现有的成形加工面临效率与力学性能难两全的困境。为此，本项目提出在挤压铸造中引入扭转剪切变形的成形新方法，拟通过实验表征和多尺度仿真模拟，探讨其组织演变机理及形性协同控制方法：1）分析挤压铸造扭转复合成形过程的物理力学特性，研究铝合金高温本构模型、成形过程界面换热和摩擦行为，构建有限元模型开展成形仿真研究，探明热-力耦合机制；2）研究铝合金回转件的组织特征和力学性能，探讨温度-压力-扭转剪切复合载荷下晶粒破碎、细化及转动规律，明确形状尺寸、工艺参数对组织性能的影响；3）构建晶粒破碎、细化的微观力学模型，耦合宏观有限元和细观粘塑性多晶体自洽模型（VPSC），建立成形过程宏细微观变形预测方法，揭示组织演变机理，优化控制成形工艺参数和变形过程，调控组织性能，形成技术原型。项目对探索高效成形高性能铝合金件的成形加工理论与控制方法具有重要意义。

本项目针对铝合金回转件现有成形技术面临成形效率与力学性能难两全的困境，创新性提出一种挤压铸造扭转复合成形新方法，采用实验表征、有限元和粘塑性多晶体自洽模型多尺度仿真模拟的方法，研究其组织演变机理及形性协同控制方法。发明了挤压铸造扭转复合一体化成型方法及成型装置，获得了A356铝合金的高温力学本构和热加工图，构建了挤压铸造扭转复合成形有限元模型和换热系数反求模型，求解了成形过程中的界面换热系数，加入扭转剪切可以提高铝合金的成形能力，工件的气孔数量减少、尺寸变小，模具-工件界面换热条件更大，组织得到了细化，性能得到了提高。构建了A356铝合金挤压铸造扭转复合成形的宏细微观仿真模型，提出了挤压铸造扭转复合成形过程宏细微观变形预测方法，构建的模型能较为准确仿真A356铝合金复合成形过程中的流变应力和织构演变，探明了成形过程宏观变形规律，揭示了A356铝合金挤压铸造扭转复合成形组织演变机理，探索了一种复合成形技术的形性控制方法。项目共发表论文17篇，其中SCI收录5篇、EI收录9篇，获国家发明专利授权4项、实用新型专利授权1项，获湖南省自然科学三等奖1项。以该项目依托培养1名研究生毕业和3名在读研究生，本科生若干名。本项目通过三年的研究工作，已完成项目的计划内容和目标。