(西北工业大学 凝固技术国家重点实验室， 西安 710072)
摘 要: 采用双热电偶法分别测得不同熔体处理A357合金的枝晶搭接点， 进而通过热分析法分别计算出枝晶搭接点的固相体积分数fcohs。 结果表明， 冷却速率和晶粒细化处理对fcohs的增大有较大影响； 而变质剂(Sr)对fcohs值的影响不明显。 分析表明， 冷却速率的提高以及晶粒细化剂的加入细化了晶粒和延缓枝晶的生长， 从而提高fcohs， 而Sr的加入只改变Si的形态， 对fcohs的影响不大。
关键字: A357合金； 枝晶搭接点； 双热电偶； 冷却速率； 熔体处理
dendrite coherency of A357 alloys
（State Key Laboratory of Solidification Processing,
Northwestern Polytechnical University, Xi'an 710072, China）
Abstract: The dendrite coherency point of A357 alloy was determined after melt-treatment by double-thermo-couple, and the solid volume fraction of coherency (fcohs)was calculated by thermal analysis. The effects of adding grain refiner Sr to the melt to modify the eutectic and the cooling rate on the increase of fcohs were investigated. The results show that the cooling rate and the addition of grain refiner significantly increase the solid volume fraction of coherency of the alloys, but the modification (Sr) has little effect on fcohs. The increase of cooling rate and the addition of grain refiner fine the grain and postpone the formation and growth of dendrite. The addition of Sr changes the morphology of Si, but has little effect on fcohs.
Key words: A357 alloy; dendrite coherency point; double-thermocouple; cooling rate; melt treatment
