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通常所说的Al-si共晶合金的变质效果是合金在冷却速度和变质元素共同作用下的结果。本文采用自制的冷速可控装置及扫瞄电镜、电子探针、差热分析等手段,较系统地研究了冷却速度对钠、锶、锑变质效果的影响。研究结果表明:钠、锶、锑均阻止初晶硅的非自发形核析出,促使α(Al)树枝晶产生。钠、锶使共晶硅由片状变为扭曲的密集分枝的纤维状,锑使散乱分布的片状共晶硅变为层片状,并使硅片变薄产生分枝,但锑的作用在高冷速下才明显,锑不能使片状共晶硅的形态发生根本变化,究其原因是各变质元素的变质阈值不同,钠的变质阈值最低,锶其次而锑为无穷大。
The so-called Al-si eutectic alloy metamorphism effect is the result of the alloy cooling rate and metamorphic elements. In this paper, the effects of cooling rate on the metamorphism of sodium, strontium and antimony were systematically studied by self-made cold-controlled devices, scanning electron microscopy, electron probe and differential thermal analysis. The results show that sodium, strontium and antimony both prevent the formation of non-spontaneous nuclei of primary silicon and promote the formation of α (Al) dendrites. Sodium and strontium change the eutectic silicon from a sheet to a twisted, densely branched fibrous state. Antimony causes patchy eutectic silicon into a lamellar shape and thinning the silicon sheet to produce a branch, but antimony The effect is obvious at high cooling rate. Antimony can not fundamentally change the morphology of lamellar eutectic silicon. The reason for this is that the metamorphic thresholds of the metamorphic elements are different, the metamorphic thresholds of sodium are the lowest, the strontium second and the antimony is infinite.