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采用可控性较好的粉末冶金工艺制备了组织细小均匀的70%(体积分数)Si/Al复合材料,研究了合金元素、粉末粒度和致密化烧结温度对硅颗粒分布、形态和尺寸的影响规律。结果表明,高体积分数(高体分)Si/Al的致密化和组织均匀性主要决定于初始粉末分散程度和高温致密化时的颗粒重排,制备温度和基体成分决定了液相含量和颗粒重排过程。硅颗粒的形态尺寸则决定于共晶析出过程。铝-硅粉末粒度比存在临界值,高于此值,难以获得均匀的微观组织。制备温度低于Al-Si共晶点时,尽管材料仍然致密,但液相含量较少,颗粒重排的贡献很小,复合材料中硅颗粒分布极不均匀。采用Al-11.2Si作为基体,复合材料中硅分布比较均匀,但由于高温制备中液相含量过多,颗粒合并长大并形成网络结构。采用Al-1.8Ni基体,复合材料的组织均匀、颗粒细小,形成的亚微米Al3Ni弥散相有效阻碍了硅互连和长大,效果显著。采用可处理强化的Al-Cu和Al-Cu-Mg基体,形成的Al2Cu和Al5Mg8Cu2Si6相有效抑制了共晶硅析出对硅颗粒合并长大的促进作用。除Al-Ni基材料之外的其他材料均形成了大尺寸AlFeSi脆性相,对组织控制没有积极作用。综合考虑基体成分和粉末冶金工艺,提出了高体分Si/Al复合材料完全致密化、以及组织细化和均匀化的关键控制因素和工艺措施。
The fine and homogeneous 70% (volume fraction) Si / Al composites were prepared by powder metallurgy with good controllability. The effects of alloying elements, powder particle size and densification sintering temperature on the distribution, morphology and size of silicon particles were investigated law. The results show that the densification and microstructure homogeneity of high volume fraction (high volume fraction) Si / Al mainly depend on the degree of dispersion of the initial powder and the particle rearrangement during high temperature densification. The preparation temperature and matrix composition determine the liquid phase content and the particle size Rearrange the process. The morphology and size of the silicon particles depend on the eutectic precipitation process. The grain size ratio of aluminum-silicon powder has a critical value above which it is difficult to obtain uniform microstructure. When the preparation temperature is lower than that of Al-Si eutectic, the contribution of particle rearrangement is small and the distribution of silicon particles in the composite is very uneven even though the material is still compact. Using Al-11.2Si as the matrix, the distribution of silicon in the composite material is more uniform, but due to the excessive content of liquid phase in the high-temperature preparation, the particles grow together and form a network structure. Using Al-1.8Ni matrix, the composite has uniform microstructure and fine grains. The formed submicron Al3Ni dispersed phase effectively hinders the interconnection and growth of silicon, and the effect is remarkable. The Al2Cu and Al5Mg8Cu2Si6 phases formed by the strengthened Al-Cu and Al-Cu-Mg matrix can effectively inhibit the eutectic silicon precipitation from promoting the combined growth of silicon particles. In addition to Al-Ni-based materials other materials have formed a large-size AlFeSi brittle phase, the organizational control has no positive effect. Taking the matrix composition and powder metallurgy into consideration, the key control factors and technological measures of complete densification of high volume Si / Al composites, as well as refinement and homogenization of the microstructure were proposed.