Experimental Research on Changing Al-15 Si Alloy Solidification Structure by Electric Pulse (EP) Treating

摘要

Experimental Research on changing Al-15%Si alloy solidification structure by electric pulse (EP) treating had been carried out. Al-15%Si molten alloy, melted with Al (99.95%) and Si (99.96%), are treated by EP in different condition, and poured into metal mold to make metallographic specimen and DSC specimen. Results of metallographic analyzing indicated that, microstructure of being treated by EP is different from untreated (original) specimen obviously. After be treated, changing of primary silicon in solidification structure is in alternate change from presenting (original specimen) to disappear (treated 30 Sec.) and then appearing (treated 60 Sec.). Accompany with the changing of primary silicon, eutectic phase is changed too. When primary silicon is disappeared, eutectic silicon is granular shape and quiet refined; when primary silicon is appeared, eutectic silicon present needle and granular shape in different size, and solidification structure is similar to original specimen. After be treated, solidification microstructure of different specimens is refined in different grade. Cooling curves of different specimens by DSC analyzing are changed apparently. On the cooling curve of untreated specimen, there is apparent inflection point of primary silicon precipitating. On the cooling curve of being treated 30 sec. specimen, there is not inflection point of primary silicon precipitating. At same time, on cooling curve of DSC of specimens being treated, degree of supercooling is increased and the freezing range is decreased.