论文部分内容阅读
采用电子束浮区熔炼技术对快速凝固法 (HRS)制备的DD32单晶进行了重熔定向凝固处理 ,对在不同扫描速率下处理的DD32单晶重熔定向凝固组织进行了深入观察分析。结果表明 ,固液界面温度梯度是电子束扫描速率的函数 ,当电子束扫描速率为 0 2mm/min时 ,固液界面的温度梯度≥ 1 0 0 0K/cm。DD32合金较高的溶质含量及相对较高的扫描速率导致成分过冷而使单晶难于形成。当电子束扫描速率大于一定数值时 ,重熔后的定向凝固组织内可以观察到细晶和粗晶两种柱状晶区 ;熔区形态的变化和强烈对流是造成此时温度场和溶质场分布不均匀的最主要原因
The DD32 single crystals prepared by rapid solidification method (HRS) were remelted and solidified by electron beam float zone melting technique. The solidification microstructure of DD32 single crystal remelted at different scanning rates was deeply investigated. The results show that the temperature gradient of the solid-liquid interface is a function of the electron beam scanning rate. When the electron beam scanning rate is 0 2mm / min, the temperature gradient of the solid-liquid interface is ≥10 000 K / cm. The higher solute content of DD32 alloy and the relatively higher scan rate lead to overcooling of the composition and make single crystal difficult to form. When the scan rate of e-beam is larger than a certain value, two types of columnar grains of fine grain and coarse grain can be observed in the remelted solidified structure. The change of the shape of the melt zone and the strong convection result in the temperature field and solute field distribution The main reason for uneven