Al-Mg合金循环连续扩展挤压-拉拔大塑性变形微观组织结构演变及强韧化机制研究

Producing ultrafine-grained (UFG) aluminum alloys by severe plastic deformation (SPD) has been widely studied as an effective way to improve mechanical properties of materials and expand their application field. However, many SPD technologies including equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) limit the size of the materials being processed to a certain extent and it is difficult to synergistically improve the strength and plasticity of the material processed. This project will propose a new SPD technology, Cyclical Continuous Expanded Extrusion & Drawing, to prepare large-scale ultrafine-grained aluminum alloy with high performance and focus on the technical basis of the new severe plastic deformation method. The microstructural evolution and regularity of the alloy during deformation process will be studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Electron Back-Scattered Diffraction (EBSD) and so on to illuminate the deformation mechanism and grain refinement mechanism. The evolution of solute atoms, dislocation configuration and precipitation phase will be studied and the role of solute atoms and precipitates in the formation of ultrafine grains will revealed. The strengthening and toughening mechanism of the ultrafine-grained alloy will be discussed based on mechanical properties tests. The relationship between the process parameters, microstructure control and the mechanical properties of the alloy will be established. The research results of this project are expected to provide theoretical basis and technical support for the development of severe plastic deformation technology to prepare large-scale aluminum alloys with high performance, and further enrich the plastic deformation theory of aluminum alloy.

通过大塑性变形制备超细晶铝合金是进一步提高其力学性能拓展其应用范围的重要途径，但目前常用的大塑性变形方法较大程度上限制了材料加工尺寸，且难以协同改善材料强度和塑性。本项目提出采用循环连续扩展挤压+拉拔变形技术制备大规格高性能超细晶铝合金，重点研究该大塑性变形方法的制备技术基础；综合运用扫描电镜等多种微观分析手段研究大塑性变形过程中合金微观组织演变过程及规律，阐明其变形机理及晶粒细化机制；研究溶质原子分布、位错组态和析出相的演变规律，揭示溶质原子和析出相在超细晶结构形成中的作用；结合力学性能测试，研究超细晶合金的强韧化机制；建立大塑性变形工艺、微观组织调控与合金力学性能之间的关系。本项目研究成果有望为开发新型大塑性变形加工技术制备大规格高性能铝合金提供理论依据和技术支撑，并进一步丰富铝合金大塑性变形理论。

Al-Mg/Al-Mg-Si合金具有中等强度、优异的成形、抗腐蚀及焊接性能，是装备轻量化的关键结构材料，已广泛应用于轨道交通、汽车、轮船、航空航天和轻工业领域。大塑性变形能够大幅细化合金晶粒，显著提高合金的力学性能。设计一条通过连续大塑性变形来制备高性能Al-Mg/Al-Mg-Si合金的可商业化生产工艺是本文的研究目标。因此，系统研究了Al-Mg/Al-Mg-Si合金在循环连续扩展挤压与拉拔、连续扩展挤压和时效过程中的显微组织与力学性能演变，揭示了Al-Mg/Al-Mg-Si合金大塑性变形和时效强韧化机制，为利用大塑性变形制备超长尺度高性能铝合金材料提供理论依据和技术支撑。.通过重点研究：（1）循环连续扩展挤压与拉拔细化和均匀化了Al-Mg合金的显微组织，协同提高了合金强度和塑性。（2）连续扩展挤压影响了Al-Mg-Si合金后续时效过程的析出行为，提高了合金的力学性能。（3）快冷连续铸造-连续扩展挤压显著细化了压Al-Mg-Si合金的晶粒，提升了合金的强度。（4）连续扩展挤压工艺成功制备了导电轨异型材，导电轨的显微组织得到了显著细化。.探明了Al-Mg合金在循环连续扩展挤压与拉拔过程组织性能演变，揭示了循环连续扩展挤压与拉拔过程合金晶粒演变规律、冷热变形下再结晶分布及晶粒细化模型。同时，揭示了不同后处理时效工艺对连续扩展挤压Al-Mg-Si合金棒材析出行为的影响，获得了强度和塑性协同提高的Al-Mg-Si合金杆料，探明了Al-Mg-Si合金在快冷连续铸造-连续扩展挤压过程组织性能演变，解释了大塑性应变Al-Mg-Si合金不能通过后时效处理进一步强化的原因。提出了一种新型高品质铝合金导电轨高效短流程制备工艺，可以实现高应变制备细晶材料，为商业化开发和应用中小型Al-Mg-Si合金加工型材奠定基础。