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采用传统铸造工艺和喷射成形技术制备了无Cr和含Cr的含Fe过共晶Al-Si合金,并利用SEM(EDS)、XRD及DSC对其显微组织、相组成及相变过程进行了研究。结果表明:2%Cr的加入不光使铸态粗大针片状的δ-Al4FeSi2相变为“骨骼状”α-Al(Fe,Cr)Si相,而且使沉积态Al-25Si-5Fe-3Cu合金中短棒状的富铁相(～10μm左右)被尺寸小于3～5μm的颗粒状α-Al(Fe,Cr)Si相所替代,从而细化的组织更有利于合金性能的提高。等温处理实验结果显示沉积态含Cr合金具有较好的组织热稳定性,其主要归因于颗粒状α-Al(Fe,Cr)Si相自身的高温稳定性,而沉积态Al-25Si-5Fe-3Cu合金热稳定差主要由于β-Al5FeSi相的长大和A7Cu2Fe相的形成。另外,结合显微组织和喷射成形工艺特点对沉积态组织形成机制分析发现α-Al(Fe,Cr)Si相有可能通过直接从液相析出和经δ-Al(Fe,Cr)Si相转变而来。
The Cr-free and Cr-containing Fe-containing hypereutectic Al-Si alloys were prepared by conventional casting and injection molding techniques. The microstructure, phase composition and phase transformation of the alloys were characterized by SEM (EDS), XRD and DSC the study. The results show that the addition of 2% Cr not only changes the as-cast δ-Al4FeSi2 phase to “skeletal” α-Al (Fe, Cr) The short rod-shaped iron-rich phase (about 10μm) in 3Cu alloy is replaced by the granular α-Al (Fe, Cr) Si phase with the size of less than 3μm to 5μm, so that the refined structure is more conducive to the improvement of alloy performance. The results of isothermal treatment show that the as-deposited Cr-containing alloy has good thermal stability, which is mainly attributed to the high temperature stability of the granular α-Al (Fe, Cr) Si phase, while the deposited Al-25Si-5Fe The thermal stability of -3Cu alloy is mainly due to the growth of β-Al5FeSi phase and the formation of A7Cu2Fe phase. In addition, the formation mechanism of the as-deposited microstructure and the characteristics of the spray forming process are analyzed. It is found that the α-Al (Fe, Cr) Si phase can be precipitated directly from the liquid phase and transformed by δ-Al (Fe, Cr) Si phase Come.