Pb-Sn合金三次树枝晶的形成判据

A Criterion for Formation of Pb-Sn Alloy's Tertiary Dendrite

在定向凝固条件下对Pb Sn合金的树枝晶生长进行了探讨 ,发现三次枝晶只能出现在过共晶区域。一次枝晶间距与二次枝晶间距的比值大小对三次枝晶的形成有直接的影响 ;较小的生长速度和较高的温度梯度有利于三次枝晶的形成。在此基础上提出了三次枝晶的形成判据 ,并与试验现象进行了对比分析。

Dendrite growth has been studied on directionally solidified hypo or hyper eutectic Pb Sn alloys. It is found that the formation of tertiary dendrite only takes place in the hypereutectic zone. The ratio of primary dendrite arm spacing to secondary arm spacing has direct influence on the formation of tertiary dendrite. In addition, Greater temperature gradient and smaller growth velocity are beneficial to its formation. A criterion for the formation of tertiary dendrite has been proposed and contrastly analyzed with the experimental results.