针状β″相和细小片状η′相协同作用强化Al-Mg-Si-Zn合金及机制

项目名称： 针状β″相和细小片状η′相协同作用强化Al-Mg-Si-Zn合金及机制

项目编号： No.51501152

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 一般工业技术

项目作者： 杨文超

作者单位： 西北工业大学

项目金额： 21万元

中文摘要： 汽车轻量化目标的实现要求车体用Al-Mg-Si系合金具有更高的强度，而借助纳米析出相强化是提高其力学性能的主要途径之一。强化相的类型、尺寸和体积分数是决定其力学性能的关键。因此，在Al-Mg-Si系合金当中获得一定的、具有高体积分数的纳米强化相组织，一直是国内外研究的热点问题。本项目以Mg过剩型Al-Mg-Si系合金为研究对象，通过Zn原子的添加消耗过剩的Mg原子，探索Zn添加对合金凝固组织及时效硬化规律的影响，通过优化合金成分和预拉伸+时效热处理工艺，在合金中建立MgZn2相和Mg2Si相两种不同的析出路径，探讨它们之间的脱溶竞争关系，以实现合金成分、预拉伸和脱溶沉淀之间的协同控制，最终在Al基体中获得高体积分数分布的两种纳米强化相（针状β″相和细小片状η′相）的共存组织，利用它们的协同作用，阻止位错运动，提高合金强度，为探索高强Al-Mg-Si系合金的开发和应用提供理论和技术基础。

中文关键词： Al-Mg-Si合金；时效硬化；微观组织；体积分数；透射电镜

英文摘要： The application of Al-Mg-Si based alloys is one of the most interested areas for lightweighting structure of automotive materials, in which the strength increase of conventional Al-Mg-Si alloys is the main focus over the world. The strengthening from the nano-precipitates is one of the most effective ways in improving the mechanical properties of Al-Mg-Si alloys. The type, size and volume fraction of the precipitates are vital in determining their mechanical properties. Therefore, it is a hot topic for research and development to obtain the specialized precipitates at an appropriate volume fraction. In this project, the excess Mg-type Al-Mg-Si alloys are used to investigate the influence of Zn addition on the solidification and age hardening behavior where the addition Zn atoms can be used to consume excess Mg atoms. Based on the optimization for the alloy composition, pre-stretching and heat treatment process, it is aimed to establish two different strengthening paths by Mg2Si and MgZn2 precipitation through exploring their competition relationship using the collaborative control between the alloy composition, pre-stretching and precipitation. The key findings are to establish the effectiveness of strengthening offered by a coexistence microstructure of two nano-strengthening phases (the needle-shaped β″ phases and fine disk-shaped η′ phases) with high volume fractions in the Al matrix. This microstructure is capable of improving the strength of Al-Mg-Si based alloys by enhance the effectiveness of preventing the dislocation movement. By the end, the project will provide a theoretical and technical foundation in understanding the high strength Al-Mg-Si-Zn series alloys.

英文关键词： Al-Mg-Si alloys;Age hardening;Microstructure;Volume fraction;TEM