【摘要】 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。更多还原

【Abstract】 Several 70%Si/Al composites with refined and unique microstructure were prepared by using well-controlled P/M technique.The influence of matrix composition,particles size and consolidation temperature on particle distribution,morphology and particle size of Si were investigated.The results revealed that densification and homogeneity of the composites mainly depended on the powder disperse and particle-rearrangement which was enabled by sufficient liquid phase with appropriate composition during consolidation.However,the morphology and size of Si depends was controlled by the precipitate of Al-Si eutectic.It implied that,there existed a critical particle size ratio of Al to Si,over which it was very difficult to obtain uniform composite microstructure.Also,when the HIP temperature was lower than Al-Si eutectic temperature,it was difficult to achieve homogeneous particle distribution due to low content of liquid phase and hence the absence of particle-rearrangement,although the composite was densified.Composite with Al-11.2Si matrix had homogeneous microstructure but abnormally coarsened and interconnected Si.While,the Al-1.8Ni matrix composite had homogeneous and refined microstructure was used.The sub-micro stable dispersions of Al3Ni were formed,which significantly refined the Si particles.Particularly,the heat-treatable Al-Cu and Al-Cu-Mg alloys matrix were proposed to modify the eutectic Si and hence suppressed Si coarsening by precipitations of Al2Cu and Al5Mg8Cu2Si6.In addition,large size brittle AlFeSi phases were formed in the composites excepted for the one with Al-Ni alloy matrix,which were thought to have no positive effect on the microstructure modification of Si/Al.In all,some keys to achieving high-Si composites with refined and homogeneous microstructure were proposed based on the composition and P/M process controlling.更多还原