SiCp/Al-Si复合材料界面效应与多尺度第二相协同作用下的组织演变与强化机理研究

In the preparation process of Silicon carbide reinforced aluminum-silicon matrix composites, because heat/stress field coupling effects, interfacial reaction and the multi-scale second phase particles precipitation appear in the microstructure, the physical and mechanical properties of the composites are difficult to control, therefore the combination performance is poor and the applications in the field of aviation, aerospace and space are restricted seriously. In view of this, on the basis of preliminary studies, the influence of the pretreatment process of the SiC powder on particle morphology and phase composition is analyzed and the law of the supersaturated solid solution element during aging precipitation in rapid solidification Al-Si powder is researched, at the same time the effects of preparation process variables on the material microstructure and properties, the thermodynamics and dynamics conditions of the composite interface reaction and the thermodynamic stability of the reaction resultant are investigated systematically, furthermore the interfacial reaction mechanism is reavealed and the interfacial reaction model is established. After the multi-scale second-phase precipitation mechanism is clarified, and the microstructure evolution and interaction strengthen mechanisms in the synergistic action of interface effects and the second phase are reavealed, the preparation process variables and component design criteria are built and the powder metallurgy production technology of SiCp/Al-Si composites is offered, therefore the scientific issues about performance under the multi-scale synergistic action of the composite interface effect and the second phase are resolved. The theoretical basis and technical support for engineering applications of the lightweight, low expansion, high strength aluminum matrix composites are provided.

粉末冶金制备SiCp/Al-Si复合材料过程中受热/应力场耦合作用，微观组织结构中出现界面反应及第二相多尺度析出现象，使其物理性能和力学性能难以控制，综合性能较低，严重制约了其在航天及空间领域的应用。项目在前期研究工作基础上，分析SiC粉体预处理工艺对颗粒形态、组成相结构的影响，探讨制备过程中过饱和固溶元素的时效析出规律，系统研究制备工艺变量对复合材料微观结构和性能的影响、复合材料界面反应的热力学、动力学条件及生成物的热力学稳定性，揭示界面反应机理，建立界面反应模型。阐明多尺度第二相析出机理，揭示界面效应与第二相协同作用的组织演变规律、交互强化机制，构建制备工艺变量及成分设计准则，提出粉末冶金法制备SiCp/Al-Si复合材料工艺制度，解决复合材料界面效应与多尺度第二相协同作用下的组织与性能关系的科学问题。为轻质、低膨胀、高强度铝基复合材料的工程应用提供理论依据和技术支撑。

SiCp/Al-Si复合材料具有轻质、低膨胀和优异的综合性能，广泛应用于空间工程、电子封装等领域。为解决复合材料界面效应与多尺度第二相协同作用下的组织演变与性能关系的科学问题，从复合材料界面结构的表征及形成机制、第二相的析出与演变、交互强化机制、性能调控及可控制备等方面开展研究工作，经努力全面完成了项目计划任务。构建了SiCp/Al-Si 复合材料制备工艺制度，阐明了多尺度第二相析出与界面反应机理，揭示了界面效应与第二相协同作用的组织演变规律以及交互强化机制，发展了复合材料强化理论。（1）高温氧化处理是综合性能最好的SiC颗粒预处理工艺，粉末冶金法+热挤压是优异的SiCp/Al-Si复合材料制备方法。（2）SiCp/Al-Si复合材料界面结构及界面产物与SiC颗粒预处理相关。原始态SiCp/Al-Si复合材料中SiC/Al界面以干净界面为主，高温氧化态复合材料中非晶型界面占主导地位，并伴有少量的反应型界面。反应生成物MgAl2O4尖晶石与SiC和Al均形成半共格界面；Si/Al界面为干净界面。（3）Si相的粗化是通过弥散分布的小颗粒Si的溶解和大颗粒Si的长大来实现的，析出相Al5Cu6Mg2的时效析出演变过程为：过饱和固溶体→GP区→δ"相→δ'相→δ相。（4）建立了SiC颗粒，Si颗粒和纳米析出相Al5Cu6Mg2混合增强下复合材料的强化机制，除了SiC，Si颗粒的载荷传递、细晶强化、热错配强化之外，纳米相（Al5Cu6Mg2）沉淀强化对复合材料强化的贡献值较大。随着时效时间的增加颗粒状Al5Cu6Mg2相引起的强度增量都是先增加后减小，Al5Cu6Mg2相引起的强度增量在时效时间为6h时达到峰值。（5）添加纳米SiC颗粒和CeO2可细化基体组织晶粒和Si颗粒，提高Si颗粒分布均匀性，提高复合材料的综合性能。本研究完善和深化了多元多尺度颗粒增强金属基复合材料的组织控制及强化理论，为开发高质量的空间工程材料提供了理论与实验依据。