“铝包碳化硅”复合粉高压烧结制备复合材料及其机理研究

SiC particle reinforced aluminum matrix composites posses excellent mechanical properties and physical properties such as low density, high specific strength and specific rigidity, low thermal coefficient of expansion, high thermal conduction, which can be extensively used in aerospace, military affairs, electric information areas. In order to solve the problems in preparing this kind of materials with PM(powder metallurgical) process, such as low compactness and segregation of SiC particles, a new technique of high pressure sintering technology with composites powder made of “Al-coated SiC powder” was developed. Simultaneously, preparation and quality control of the powder, evolution of microstructures and properties of the composites, and mechanism of interfacial bonding were investigated. This study aims at: 1) coating mechanism of SiC coated with aluminum and the evolution of coated particles; 2) formation law of interface structure of composites; 3) the microstructure evolution and densification mechanism during high pressure sintering of SiCp/Al composites. This study will offer a new technique for SiCp/Al composites spray forming, reveal the influence of parameters on the composites during high pressure sintering and clarity the mechanism of interfacial bonding and microstructure evolution. In addition, the research can provide a theoretical support for the practical application of metal matrix composites.

SiC颗粒增强铝基复合材料以其低密度、高比强度、比刚度、高导热性、低线膨胀系数等优良性能使其在航空航天、军工、电子通信领域具有重要的使用价值。针对粉末冶金方法制备该材料存在的致密度低、SiC颗粒分布不均匀等问题，本研究提出“铝包碳化硅”复合粉高压烧结成形技术的概念，对“铝包碳化硅”复合粉的制备和质量控制、复合材料组织性能影响规律和界面结合机制等方面进行系统研究，着重解决：1）“铝包碳化硅”包覆机制以及包覆颗粒演变规律；2）高压条件下复合材料界面结构形成规律；3）高压烧结组织演变规律及致密化机理。本研究将形成碳化硅颗粒增强铝基复合材料高压烧结新方法；揭示高压条件下，工艺参数对复合材料成形过程的影响规律；明晰高压条件下SiC颗粒与基体之间的界面结合机理以及组织形成机制，为金属基复合材料的应用提供新的理论支撑。

本项目以碳化硅颗粒增强6061铝复合材料为研究对象，采用高压烧结技术制备SiCp/Al复合材料，研究了碳化硅颗粒体积分数、烧结压力和烧结温度工艺参数对制备的复合材料组织演变、界面结合以及性能的影响规律。研究发现: 纳米铝包碳化硅的混粉工艺可以解决碳化硅颗粒的团聚问题。烧结温度对复合材料组织性能有较大的影响，随着烧结温度升高， SiCp/Al复合材料的致密度、硬度和耐磨性先增加后降低，在烧结温度为650℃和750℃时，碳化硅颗粒出现了局部的轻微团聚，导致复合材料的致密度、硬度和耐磨性降低。研究发现，当烧结温度超过600℃时，SiC颗粒与基体的界面产生过渡层，发生界面反应，生成Al4C3脆性相，不利于复合材料组织性能的提高。此外，随着碳化硅体积分数的增加，硬度增加，耐磨性提高，致密度有所下降。烧结压力的增加有利于复合材料致密度和硬度的增加。但是，过高的烧结压力会导致耐磨性下降。