墩挤组合大变形制备超细微结构铝合金制备技术研究

The application of Al alloy is increased in different fields, which requires excellent performance, ultra fine grained (UFG) microstructure is the only method to improve its performance in which its ductility is not damaged, severe deformation method has some particular advantages in the preparation of bulk UFG microstructure materials. In view of the existing problems such as severe plastic deformation preparation method, formation mechanism and the relationships of microstructures and performance for UFG microstructure materials, the uniform and stable Al alloy with UFG microstructure will be prepared by severe deformation method of compression and extrusion in this research. The prediction model, numerical simulation during the course of compressin and extrusion, mold design, preparation technology, grain deformation, texture evolution, distribution state and strengthening effect for second phase, strengthening mechanism for microstructure, rotation and sliding movement for grain boundaries, dislocation configuration, change and rotation for crystallographic orientation will be investigated, the controlling principle for microstructure and orientation, grain refinement mechanism and the relationships of UFG microstructure and performance will be obtained, the formation mechanism of UFG microstructure for Al alloy will be revealed, and the technology system of Al alloy with UFG microstructure prepared by severe deformation method of compression and extrusion will be determined. The research achievements can provide a new method for the preparation of bulk UFG microstructure materials with high performance,in company with the corresponding theoretical basis and technical support.

铝合金材料在不同领域应用的日益增加，对其性能要求也越来越高，超细微结构化是提高其性能且不损害延性的唯一强化方法，而大塑性变形方法在制备块体超细微结构材料方面具有独特的优势。针对目前超细微结构材料的大塑性变形制备方法、形成机制及微观组织结构与性能关系方面存在的问题，本研究提出采用等通道挤压和镦粗组合大变形方法制备均匀、稳定的超细微结构铝合金。通过预测模型、镦挤过程数值模拟、模具设计、制备技术基础、晶粒变形过程、织构演变过程、第二相分布状态及强化作用、微结构强化机制、晶界转动滑动变化过程、位错组态、晶体学位向变化转动过程等研究，获得超细微结构的组织及取向控制原则、晶粒细化机制及超细微结构与性能之间的关系，揭示铝合金超细微结构的形成机制，形成镦挤组合大变形方法制备超细微结构铝合金的制备技术体系。本研究成果有望为高性能块体超细微结构材料探索出一种新的制备技术，并提供相应的理论依据和技术支撑。

通过镦挤变形过程有限元分析模型的建立和数值模拟，为模具的设计和改进提供了有效的依据；优化设计并制造出试验用挤压和镦粗模具；采用复合镦挤组合大变形技术ECAP-CCDC工艺制备出具有超细微结构的6061、1061和7003高强铝合金；研究了复合镦挤变形及退火过程组织变化、位错形成与作用、第二相析出与强化、取向变化、晶界特征变化，获得了镦挤组合大塑性变形技术制备超细微结构铝合金的组织演变过程、织构组分演变过程及晶粒细化机制研究；通过不同工艺过程及不同组织状态铝合金的硬度、强度、韧性等性能表征及拉伸断口分析，获得了具有不同超细微结构组织铝合金的力学性能和塑韧性之间的关系。本项目通过镦挤组合大塑性变形法制备出具有超细微结构的高强铝合金。其超细微结构各向异性性能好，同时在较少的加工变形次数就达到了细化晶粒的目的。镦挤组合大变形技术制备超细微结构铝合金对材料的组织形成可根据成形工步不同进行有效控制，对材料强化作用具有重要理论意义。同时，获得超细微结构可以提高材料的强韧性能，从而达到延长材料使用寿命、提高生产效率，降低生产成本目的，在各种高性能铝合金零件及器件的制造领域应用前景广阔。采用该镦挤组合大变形技术来研发新一代的超细微结构高强铝合金材料，必将加快有色金属新型材料的生产，提升有色金属及其合金深加工的能力和水平，对有色金属新材料深加工技术的发展起到重要的推动作用。