Al-Mg-Si合金重复连续挤压大塑性变形微观组织演变规律及改性机理研究

Al-Mg-Si alloys, known as thermomechanical treatment strengthening alloys, are widely used for lightweight structural materials and conductor. However, there is a big challenge to gain the optimal mechanical properties concurrently on strength and plasticity. Severe plastic deformation can refine grains and enhance property of alloys with limited industrial application, combined with the special thermodynamic conditions, therefore, this project proposes a novel method to put severe plastic deformation on Al-Mg-Si alloys into practice using repetitive continuous extrusion forming. The method skillfully combines severe plastic strain-induced continuous dynamic recrystallization and dynamic precipitation to achieve an elegant combination of fine (sub) grains and precipitates, which settles the trouble of higher strengthen accompanying with lower plasticity and then improves the comprehensive properties of the alloys simultaneously, such as strength and plasticity. The evolution of microstructure and properties of Al-Mg-Si alloys during repetitive continuous extrusion forming under high temperature, low temperature and both alternately will be studied. The mechanisms of severe plastic strain-induced continuous dynamic recrystallization and dynamic precipitation during repetitive continuous extrusion forming, the relationship between the properties and microstructure and coupling mechanics model are to be explored. The physical natures of synergistically enhanced strength and plasticity properties in Al-Mg-Si alloy by repetitive continuous extrusion forming are suggested to be revealed. The works will be the theoretical bases for effectively producing medium and small standard aluminum alloy products with high level performance under severe plastic deformation utilizing repetitive continuous extrusion forming technique.

Al-Mg-Si合金是一种可形变热处理强化铝合金，广泛用作轻量化结构和导体材料。然而，合金的强度与塑性等性能往往难以保证一种最佳组合。本项目基于大塑性变形可以细化组织而改进合金性能但商业化应用有限的现状，结合连续挤压特殊的变形热力学条件，提出采用重复连续挤压对Al-Mg-Si合金进行大塑性变形，巧妙结合大变形应变诱发连续动态再结晶及动态析出使合金同时获得均匀细小的（亚）晶粒组织和析出强化相，达到协同改良合金综合性能的目的。项目主要研究Al-Mg-Si合金重复连续挤压过程中的位错组态、亚晶粒与新晶粒形成及析出相形态、尺寸、分布、成份及结构的演变规律，探索重复连续挤压大变形诱发连续动态再结晶及动态析出的作用机理，以及合金宏观性能与微观组织特征的相关性，揭示重复连续挤压变形协同提高合金强度与塑性等性能的物理本质，为商业化利用该技术有效制备中小规格铝合金材料并改进其性能提供理论基础。