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利用高速摄影仪和SEM研究了RE对Al-80%Si合金凝固过程中再辉界面形貌、初生Si形貌和凝固后组织的影响.结果发现,加入RE前后的Al-80%Si合金均存在2个临界过冷度DT1和DT2,在过冷度小于DT1时,初生Si的形貌为粗大的长片状,表面有明显的棱角;过冷度大于DT2后,合金在凝固过程中的再辉界面为平面状,凝固后的初生Si形貌为均匀、细小、表面有光滑凸起的球状,并且晶粒表面的棱角消失;当过冷度在DT1与DT2之间时,合金在凝固过程中的再辉界面为树枝状,凝固后的初生Si形貌部分为表面有棱角的片状和块状,部分为表面无棱角的球状.对于Al-80%Si合金而言,DT1和DT2分别约为132和250 K.RE能降低Al-80%Si合金DT1和DT2的值,对于Al-80%Si-1%RE而言,DT1和DT2分别约为60和199 K.
The effect of RE on the interface morphology, the morphology of primary Si and the microstructure of Al-80% Si alloy after solidification was investigated by high-speed photogrammetry and SEM. The results show that Al-80% Si alloy before and after adding RE There are two critical undercooling DT1 and DT2, when the undercooling is less than DT1, the morphology of primary Si is coarse long flake, the surface has obvious edges and corners; undercooling is greater than DT2, the alloy in the solidification process The re-enamel interface is planar, the morphology of the primary Si after solidification is uniform and fine, the surface has a spherical shape with a smooth convex surface, and the edges and corners of the crystal grain disappear. When the degree of undercooling is between DT1 and DT2, The re-enamel interface in the process is dendritic, and the primary Si morphology after solidification is flake-like and block with angular surface and partly spherical with no surface. For Al-80% Si alloy, DT1 and DT2 Respectively, about 132 and 250 K. The RE reduces the values of DT1 and DT2 for Al-80% Si alloys, with DT1 and DT2 being about 60 and 199 K for Al-80% Si-1% RE, respectively.