【摘要】 铝合金具有低密度、高比强、耐腐蚀等优点，作为结构金属材料应用广泛。工业级铝合金的高强度主要来源于纳米沉淀相颗粒对位错的钉扎，其微米晶粒尺寸下的时效析出与强韧化行为已得到了大量研究，并在工程上实现了人工调控。伴随着各种加工制备方法的成熟完善，具有超细晶、纳米晶等细小晶粒尺寸的铝合金材料得到了越来越多的关注，以期待突破铝合金相对较低的强度。但是铝合金的时效析出行为却呈现出明显的晶粒尺寸效应，即在细小晶粒的高能量状态下，由于晶体缺陷数密度增大以及晶界能量升高，溶质原子倾向于不可控制地在晶界上析出并快速长大粗化，强化效果不足、同时还易于引起晶界处应力/应变集中并导致早期断裂。抑制晶界析出、实现高强塑性匹配是细小晶粒铝合金所面临的难题，也是其工程化应用的前提。以Al-Cu合金作为模型材料，讨论分析了不同晶粒尺寸下的时效析出行为，提出了微合金化和高浓度空位调控的微观组织设计策略，将为新型细晶铝合金的开发提供参考。更多还原

【Abstract】 Aluminum(Al) alloys are widely used in various industrial fields, due to their low density, high specific strength, excellent corrosion resistance and other advantages.The high strength of Al alloys is derived from nanosized precipitates that greatly block moving dislocations.The precipitation and hardening in commercial coarse-grained Al alloys has been extensively studied and could be artificially tuned in engineering applications.With the advances in processing and preparation methods, Al alloys with smaller grains, such as ultrafine grains and nano grains, have received increasing attention, in the hope of breaking through in their strength.However, the aging precipitation behavior of aluminum alloys exhibits a significant grain size effect,that is, solute atoms tend to precipitate in an uncontrollable manner at grain boundaries and coarsen fast when the grains reduce to small size.The unfavorable precipitation, mainly associated with the enhanced crystal defects and improved high-energy grain boundaries, will lead to insufficient strength and premature fracture.It is challenging to suppress grain boundary precipitation and optimize strength-ductility combination, which are requisites for applications of small-grained Al alloys.With Al-Cu alloys as a kind of model Al alloys, the paper discusses the precipitation at different grain sizes, and proposes a microalloying strategy in combination with high-concentration vacancies for microstructural design.This study may provide reference for the development of high-performance Al alloys that have refined grains.更多还原