Al-Mg-Si导线材料的Sc微合金化及其微观组织-性能关联

This project will be focused on ultrafine-grained Al-Mg-Si conductor materials, which are microalloyed by Sc and characterized by microstructural features with intergranular/intragranular dual distributions of nanosized particles, derived from two-stage aging treatment. The effects of composition, microalloying element, and aging treatment on the microstructural evolution, precipitation behaviors as well as on the properties, including strength, electrical conductivity, and heat-resistance property, will be comparatively studied. This project is aimed to (i) demonstrate the two-stage precipitation characteristics in the metal conductor materials with ultrafine-sized grains; (ii) clarify the Sc microalloying mechanism at this length scale; (iii) explore the possible interaction between the microalloying elements and the main alloying elements; and (iv) correlate the microstructures with the properties of the ultrafine-grained Al conductor materials. Corresponding models will be developed to quantitatively describe the relationships between the microstructural parameters and the strength, electrical conductivity, and high-temperature properties, with which the main influencing factors will be artificially controlled to optimize the comprehensive properties. In particular, development of a new kind of high-performance Al-Mg-Si-Sc conductor materials will be centered by controlling the Sc content and promoting the preparing procedures, which have microstructural features with Mg2Si precipitates dispersed within the grain interior and Al3Sc dispersoids located at grain boundaries. These results will be helpful for understanding the precipitation behaviors and their tailoring approaches in ultrafine-grained metal conductor materials. Besides, they will be reference for the alloy design and process optimization of high-strength, high-conductivity, and excellent heat-resistance Al alloy-based conductor materials.

本申请将以Al-Mg-Si超细晶导线材料作为研究对象，以Sc作为微量添加元素，通过双级时效处理形成纳米第二相颗粒晶内/晶界双层级分布的微观组织，对比研究合金成分、微合金元素含量和时效工艺对微观组织演变、时效析出行为以及对强度、电导率和耐热性能的影响。阐明超细晶金属导线材料的双级析出特性；澄清该尺度下微合金化元素的作用机理；探索主合金元素与微合金元素之间可能的相互作用；在此基础上建立超细晶铝合金导线材料微观组织与性能之间的关联并构建相应的理论模型，据此优化相关影响参量以获得优异的综合性能。重点通过微合金量及相应制备工艺的调控，获得晶内纳米Mg2Si相和晶界Al3Sc双层级颗粒分布的微观组织，开发高性能Al-Mg-Si-Sc合金导线材料。研究结果不仅有助于从机理上理解超细晶铝合金导线材料中的时效析出行为及其调控原则，同时也为高强、高导、耐热铝合金导线材料的合金设计和工艺完善提供借鉴和参考。

电力行业的快速发展对高强、高导铝合金导线材料提出了新的性能要求，而强度与电导率之间“此消彼长”的互斥关系却制约了铝合金导线综合性能的突破。本项目针对Al-Mg-Si导线材料在强度、电导率和耐热性上的多性能需求，采用Sc微合金化调控手段，通过加工变形和热处理工艺的优化匹配，制备出具有超细晶晶粒以及Al3Sc和Mg2Si多重纳米第二相颗粒弥散分布的多层级微观组织结构。其中超细晶和晶内纳米第二相颗粒起到主要的强化作用；大尺寸Al3Sc纳米第二相颗粒界面高密度几何必须位错促进了其后Mg2Si第二相颗粒的时效析出，提高了电导率；而Al3Sc颗粒的弥散分布以及对晶界的钉扎则保证了热稳定性。在宽幅Mg和Si含量范围内以及不同的加工/热处理工艺处理下，系统研究了合金成分、微合金化元素Sc添加量以及制备工艺对微观组织演变、时效析出行为以及对强度、电导率和耐热性能的影响规律。阐明了超细晶Al-Mg-Si导线材料Sc微合金化的多级析出特性；澄清了不同晶粒尺度下Sc微合金化元素的作用机理；并探索了主合金元素与微合金元素之间的相互作用。基于Mg/Si比以及晶粒尺寸对Al-Mg-Si-Sc导线析出行为与力学/电学性能影响的研究结果表明：在优化的Sc添加下，粗晶Al-Mg-Si-Sc合金中β”-Mg2Si颗粒主要在晶内析出，材料强度严重依赖于Mg/Si比，而电导率却对Mg/Si比不敏感。与Mg过量相比，Si过量(Mg/Si比<1)促进了β”-Mg2Si颗粒的析出，因此强度更高；而在超细晶合金中则反过来，对Mg/Si更敏感的是电导率而不是强度，其中Si过量合金的电导率高于Mg过量的合金。进一步在性能测试和微观表征的基础上，建立起了超细晶铝合金导线材料微观组织与性能之间的关联并构建了相应的理论模型。同时面向耐热性铝合金导线的迫切需求，积极开展了Al-Zr和Al-Cu体系铝合金导线的相关研究，对本项目的Al-Mg-Si合金导线研究起到了促进作用和推动效果。