基于双尺度增强体与第二相协同作用的SiCp/Al-Si基复合材料微观结构演变与动态软化机制

The research of the high-performance SiCp/Al composite due to the different physical property of SiCp and Al has become the forefront around the world. The combination property of SiCp/Al composite can be improved through the micro-scaled reinforcement combined with nano-scaled reinforcement. This project focused on the important scientific issues of dual-scaled SiCp/Al-Si composite, such as the ratio of the micro-scaled with the nano-scaled reinforcement, the microstructure evolution, distribution of the reinforcement, interface, the second phase characteristics, dynamic softening mechanism and macro and mesoscopic mechanical behavior during the powder metallurgy sintering and the thermal deformation process. And the dynamic recovery and dynamic recrystallization mechanism under the effect of the multi-field is the most important part. The responding mechanism of microstructure, thermal deformation behavior and property can be revealed. The dynamic recrystallization model and processing map can be established. And the rule of the ratio of dual-scaled reinforcement and hot working process can be formatted. The establishment of theoretical basis system of the component, structure design, performance adjustment and preparation of SiCp/Al-Si composite enhanced by dual-scaled reinforcement can provide theoretical basis and technical support for the preparation technology and engineering application of the high performance composite materials.

利用SiCp和铝合金不同的物理属性，发展高性能SiCp/Al基复合材料已成为世界各国研究的前沿。采用微米和纳米双尺度SiCp增强铝基复合材料的综合性能。项目以双尺度SiCp/Al-Si复合材料为研究对象，拟对复合材料双尺度配比，粉末冶金烧结及热变形过程中微观结构演变、增强体分布形态、微观构型，界面结合状态、第二相特性、动态软化机制、宏细观力学行为这一重要科学问题开展研究。重点研究多场耦合作用下微观结构演变、双尺度配比及微观构型、宏细观力学行为、双尺度颗粒与第二相协调作用下的动态回复与动态再结晶机制，揭示微观构型、热变形行为、性能三者的响应机制，构建动态再结晶模型及热加工图，形成复合材料双尺度配比调控准则及热加工工艺准则。建立双尺度颗粒增强SiCp/Al-Si复合材料组分与构型设计、性能调控、成型制备的理论基础体系，为高性能复合材料制备技术及工程应用提供理论依据和技术支撑。

采用微米加纳米双尺度SiCp能够增强铝硅基复合材料的综合性能。目前，双尺度SiCp/Al-Si复合材料热加工成型过程中双尺度增强体与第二相协同作用下的复合材料微观结构演变及动态软化机制研究缺失，制约了复合材料的发展和工程化应用。项目研究了双尺度颗粒配比及复合材料微观构型，探明了双尺度SiCp/A356复合材料的双尺度配比为80nm 2vol.%+10um 23vol.%，颗粒均匀分布其性能最佳，其强韧化机制为载荷传递强化、Orowan强化、热错配强化、细晶强化、第二相强化、固溶和时效强化机制交互作用；探明SiCp/A356复合材料中第二相析出转变规律为：几纳米的圆形GP区→十几纳米长的针状β″相(共格)→一百多纳米长的棒状相β′（半共格）→非共格β相（Mg2Si）；研究了微米、纳米、（微米+纳米） 双尺度复合材料的变形行为，（80nm 2 vol.%+10um 13 vol.%）SiCp/A356双尺度复合材料的热变形激活能为468 KJ/mol，构建了其本构方程；探讨了其热变形过程中微观结构演变规律与动态软化机制，提出动态再结晶临界变形条件，给出了临界应变与Z参数之间的函数关系；建立了动态再结晶晶粒度模型；阐明其动态再结晶软化机制主要有晶界弓出机制、颗粒诱发形核机制和亚晶旋转诱导形核机制；提出双尺度复合材料的最佳热加工工艺窗口为：应变速率为0.62~5s-1、变形温度为495~518℃。揭示了双尺度SiCp/A356复合材料在成型加工制备中微观组织形成与演变规律、软化机制、热变形行为、宏细观力学行为这一科学问题。完善了双尺度复合材料制备的理论基础和技术体系，为双尺度颗粒增强复合材料制备技术及工程应用提供理论依据和技术支撑，对促进我国高性能颗粒增强铝基复合材料制备技术发展和应用具有重要的意义。