动态多向塑性变形制备高强韧纳米结构铝合金的微/纳观机理及其热稳定性研究

The preparation of nano-structured metallic materials and the exploration of their excellent performance are the research focuses in the current materials academic fields. .The dynamic multiple forging technique for preparing nano-structural aluminum alloy will be explored in the present application. Advanced experimental techniques such as SEM/EBSD、TEM/HREM and APT will be comprehensively used to study the achieved nanostructure at different scales especially on the atomic scale. The mechanisms of precipitates dissolved instantaneously at low temperature and grains sharp refined instantly during the nano-structure forming process induced by adiabatic shear deformation at high strain rate, and the nano-miniaturization evolution mechanism of the micro-structure during the dynamic multiple forging deformation will be explored. The characteristics of the nano-structures especially the composition、distribution、segregation of the solute atom clusters will also be investigated. The physical essence of the nanostructure's strengthening/toughening and the mechanism of the nanostructure's thermal stability will be studied.. New techniques for preparing metallic nano-structural materials and optimizing of their performance will try to be developed, and then the foundation for engineering applications and the design principles as well as the preparing technologies of nanostructures will be established on basis of the above researches.

纳米金属材料的制备和优异性能探索研究是当下材料学界的热点。为揭示这一贯穿不同结构层次的过程本质，本项目拟探索制备铝合金体纳米结构材料的动态多向锻压DMF新技术；综合运用SEM/EBSD、TEM/HREM、APT等先进的实验技术，在不同尺度尤其是在原子尺度上进行实验研究。探究高应变速率动载下绝热剪切变形诱导的纳米结构形成过程中析出相低温瞬间溶解以及晶粒瞬间急剧细化的机制；揭示DMF变形过程中微结构纳米化的演变过程与机理；研究纳米结构特征尤其是纳米结构中溶质原子团簇的成分、分布、偏析等的原子量级特征，探索纳米结构强韧化的物理本质、以及纳米结构热稳定性的控制因素和机制。. 力图发展出金属纳米结构材料制备新技术和性能优化途径，进而为纳米结构设计原理和制备技术的工程应用奠定基础。

超细晶（纳米）金属材料的制备和优异性能探索研究是当下材料学界的热点。为揭示这一贯穿不同结构层次的过程本质，本项目探索了制备铝合金体超细晶（纳米）结构材料的动态多向锻压DMF新技术；运用EBSD/SEM、TEM等先进的实验技术，探究高应变速率动载下绝热剪切变形诱导的纳米结构形成过程中析出相低温瞬间溶解以及晶粒瞬间急剧细化的机制，揭示DMF变形过程中晶粒超细化or纳米化的演变过程与机理，以及超细晶（纳米）结构热稳定性的控制因素和机制。得到了如下研究结论：. 1.首次基于热力学、动力学阐释了铝合金绝热剪切形变过程中沉淀相瞬间溶解机制，并建立沉淀相的扰动扩散溶解模型；. 2.基于旋转动态再结晶理论，解明了绝热剪切形变过程中晶粒瞬间细化机制；. 3.揭示了铝合金动态多向塑性变形过程中晶粒细化演变特征与机制；. 4.探明了应变速率、多向/单向加载方式对铝及铝合金晶粒细化的影响规律与机制；. 5.揭示了高应变速率动态加载制备的超细晶组织、以及绝热剪切形成的纳米晶粒组织的热稳定性规律与机制。. 已在国际著名学术刊物Materials Science and Engineering A、Journal of Materials Research、Applied Physics A、Journal of Materials Engineering and Performance等上公开发表论文15篇，另有3篇在送审。. 本项目的研究成果对于发展出金属超细晶/纳米结构材料制备新技术和性能优化途径提供了实验数据与理论指导。