Comparison among chemical and electromagnetic stirring and vibration melt treatments for Al–Si hypereutectic alloys
Comparison among chemical and electromagnetic stirring and vibration melt treatments for Al–Si hypereutectic alloys
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DOI：
10.1016/j.jallcom.2006.09.039
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发表时间：
2006-12
影响因子：
6.2
通讯作者：
F. C. Hernández;J. Sokolowski
中科院分区：
文献类型：
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作者：
F. C. Hernández;J. Sokolowski
比较了化学处理和电磁搅拌振动(ESV)对390Al-Si过共晶合金的组织细化效果。Al-Si过共晶合金采用化学(即P和Sr)变质剂辅助熔体处理的方法仅限于通过活性核位(硅团聚体)的倍增来减小初生硅颗粒的尺寸。这限制了初生硅颗粒在液态时的粗化作用。本文研究了Al-Si过共晶合金ESV熔体处理后的显微组织，表明ESV熔体处理在液态和半固态是有效的。本文介绍了ESV熔体处理样品在液相线以上温度高达130℃时的显微组织。在高于液相线100℃或更高的温度下进行ESV处理，通过促进羽毛状初生硅颗粒的形成，对硅的变质效果有限。ESV处理在接近液相线的温度下(即390 Al-Si合金的温度为620℃)更有效，在这种条件下，ESV处理可以成功地变质初生硅颗粒，使其转变为“类共晶”颗粒。所得显微组织为初生无硅组织，外观与锶变质的Al-Si亚共晶组织相似。ESV和化学联合处理的使用进一步细化了Al-Si过共晶合金的组织。本文利用硅改性水平(SIML)对硅改性程度进行了量化。热分析结果与显微组织细化结果吻合较好，相关系数R2=0.89。
A comparison among the microstructure refinement between chemical treatment and electromagnetic stirring and vibration (ESV) for the 390 Al–Si hypereutectic alloys is presented. The use of melt treatments assisted by chemical (i.e. P and Sr) modifiers for Al–Si hypereutectic alloys are limited to reduce in size the primary Si particles by the multiplication of active nuclei sites (Si agglomerates). This limits the coarsening effect of the primary Si particles in the liquid state. This paper shows the microstructures of ESV melt treated of Al–Si hypereutectic alloys; such microstructures show that ESV melt treatments are effective in the liquid and semi-solid states. In this paper are presented microstructures of ESV melt treated samples at temperatures as high as 130°C above the liquidus. ESV treatments applied at temperatures of 100°C above liquidus or higher have a limited effectiveness in Si modification by promoting the formation of feathered-like primary Si particles. ESV treatments are more effective when applied at temperatures close to liquidus (i.e. 620°C for the 390 Al–Si alloy), under this condition ESV treatments can successfully modify primary Si particles transforming them into “eutectic-like” particles. The resulting microstructure shows primary Si free microstructures with similar appearance to a Sr modified Al–Si hypoeutectic microstructure. The use of combined ESV and chemical treatments further refining the microstructure of the Al–Si hypereutectic alloys. In the present paper, the Si modification level was quantified using the silicon modification level (SiML). Thermal analysis results show good agreement with microstructure refinement, showing a correlation of R2=0.89.