游离晶在铸件晶区形成中的作用

应用铸件在凝固时的倾出方法观察了工业纯铝试样在低过热度浇注时晶区的形成过程。结果表明，铸件激冷晶区是在凝固界面对密度很大的游离晶连续、大量捕获时形成的。铸件底部粒状堆积晶区是在游离晶沉降堆积后，因凝固层的增长速度小于游离晶的堆积速度，凝固在紧密堆积的游离晶间隙中进行而形成的。结果还表明，铸件柱状晶区的形成与生长并不要求高的温度梯度。

Effect of Floating Crystals on Formation of Crystal Zone in Castings

The formation process of crystal zone in commercially pure aluminum specimens when the molten being poured out at a low superheating temperature has been observed through decanting Al casting in to solidification. The results show chill crystal zone of castings is formed when the solidifying interface captures a large amount and in a continuous way the high density floating crys- tals. The equiaxed crystals piled on the crystal zone on casting bottom is for- med, while the growth rate of the solidifying front slowed down the pile rate of floating crystals, and the solidification proceeds at the gap of the higher den- sity floating crystals. The results also show the formation and growth of column crystals demand no higher temperature gradient.