基于稀土元素Sc、Zr复合改性多层-微纳结构铝合金的制备及其微观组织调控

The preparation and structural regulation of material with different scales such as micro and macro provide a new opportunity for the strengthening and toughening of metallic materials. This project intends to develop a target-determined hot extrusion process of overlapping sheets for the controllable fabrication of Al-Mg-Sc-Zr alloys with bimodal microstructures. Through the fine coordination of the Sc(Zr) contents and friction stir processing parameters, Al sheets with different structural characteristics such as coarse grains, ultra-fine grains and nano-grains could be prepared. Then the hot extrusion process of overlapping sheets with different microstructures would be introduced to produce the bimodal microstructural alloys. The effects of the deformation of the sheets and temperature on the microstructures would be systematically investigated. Then the alloy strengthen mechanism will be studied by analyzing the relation between bimodal structure, precipitated phase and dislocation slide after the annealing treatment. Meanwhile, the toughening mechanism will be researched by calculating of dislocation density difference before and after the tensile test, which followed by analyzing the relationship of dislocation distribution and species of precipitated phase. All the achievements of this project are supposed to provide new technology and theory for fabricating high performance aluminum alloys with bimodal microstructures.

纳米-微米-宏观等不同尺度上的结构设计与制备调控为金属材料强韧化研究提供了一个新的契机。本项目拟采用目标调控的“高温叠挤”工艺，实现多层-微纳结构Al-Mg-Sc-Zr合金的可控构筑，通过精细协调Sc（Zr）添加量以及搅拌摩擦加工（FSP）参数，制备粗晶、超细晶、纳米晶不同尺度结构特征材料；进而将所构筑不同尺度结构材料逐层堆叠并经高温挤压获得粗晶、超细晶、纳米晶共存的多层-微纳结构铝钪合金。系统研究变形量与时效工艺共同作用下合金塑性形变与微观组织演变行为，掌握组织结构的形成与演变规律以及调控方法；定量探索应变硬化率的变化所对应的位错密度及位错组态，探明其对多层-微纳结构铝钪合金韧性的影响机理，确立映射合金韧性与强度的位错、Al3(Sc,Zr)相及多层-微纳结构最佳模式，形成新型高性能铝钪合金的原型。以期为基于多层次多尺度组织构筑的高性能铝合金材料的发展提供理论依据和实验支撑。

纳米-微米-宏观等不同尺度上的结构设计与制备调控为金属材料强韧化研究提供了一个新.的契机。本项目采用目标调控的“高温叠挤”工艺，实现了多层-微纳结构Al-Mg-Sc-Zr合金的可控构筑，通过精细协调Sc（Zr）添加量以及搅拌摩擦加工（FSP）参数，制备粗晶、超细晶、纳米晶不同尺度结构特征材料；进而将所构筑不同尺度结构材料逐层堆叠并经高温挤压获得粗晶、超细晶、纳米晶共存的多层-微纳结构铝钪合金。系统研究了变形量与时效工艺共同作用下合金塑性形变与微观组织演变行为，掌握组织结构的形成与演变规律以及调控方法；定量探索应变硬化率的变化所对应的位错密度及位错组态，探明了其对多层-微纳结构铝钪合金韧性的影响机理，确立映射合金韧性与强度的位错、Al3(Sc,Zr)相及多层-微纳结构最佳模式，形成新型高性能铝钪合金的原型。以期为基于多层次多尺度组织构筑的高性能铝合金材料的发展提供理论依据和实验支撑。