单晶高温合金（？）C36电子束区熔定向凝固

【作者】 杨亮；

【导师】 张军；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2003， 硕士

【摘要】 本文利用了电子束区熔设备制备了各种组织形态ЖC36高温合金单晶，目的是利用电子束区熔定向凝固的方法制备单晶高温合金的工艺，为电子束技术的发展与应用提供一定的技术指导。 本文中建立了一维热传导的数学模型，大致估算了熔区固液界面处的温度梯度分布；利用ESZ1.5／5型电子束区熔设备重熔ЖC36单晶高温合金试样，在加热功率突然为零的情况下得到了ЖC36高温合金的各种凝固组织形态。整个实验中，加热功率基本保持49w不变，并且抽拉速率的变化范围为0.1mm／min-6.0mm／min。 最后利用光学显微镜、扫描电镜、电子探针及X射线仪对所制备的各种组织形态进行观察与测试。主要得出如下结论： (1)根据熔区内的热平衡，建立数学模型，得出了固液界面处的温度分布。 Ⅰ在不考虑熔区长度不变的条件下，固液界面前沿的温度梯度随抽拉速率的增加而增加。 Ⅱ对于确定成分的合金，在熔区充分稳定的条件下，可以认为其固液界面处的温度梯度变化不大。 Ⅲ结果表明，根据此模型计算出的温度梯度与利用成分过冷得出的结果是很相符的；对于ЖC36高温合金来说，温度梯度值大致为350k／cm。 (2)在加热功率基本保持不变的条件下，随着区熔速率的增加，ЖC36合金的凝固组织由平界面向胞状及枝状组织的转化，枝状(胞状)单晶枝干上的γ′相比枝间上的要细，并且要规则一些；ЖC36高温合金中的Al、Ti、Mo等元素为正偏析元素，而w、Co为负偏析元素，枝晶偏析随着抽拉速率的增加呈现先增大后减小的趋势，在低速凝固阶段，枝晶偏析随区熔速率的增大而增大，在中速凝固阶段，枝晶偏析随凝固速率的增加而减小，W、Co、Cr等元素的枝晶偏析比均趋于1；胞晶一次间距小于胞枝转变点附近粗枝晶的一次枝晶间距，一次枝晶间距的最大值出现在胞枝转变后的粗枝生长阶段，然后随着抽拉速率的不断增加，一次间距不断减小，并且γ／γ′共晶的尺寸是减小的。 (3)所制得的各种不同凝固组织单晶的[100]晶向与试样轴向的偏离度在10°。 通过本文的实验及分析可以看出，由于电子束区熔设备的能量密度大，可以获得很大的温度梯度，因此利用该设备制取ЖC36高温合金单晶是可行的。更多还原

【Abstract】 In this article , ЖC36 single crystal superalloy is gotten by eletron beam(EB) zone melting facility at the basis of the former’ research work., the aim is to supply technique supportment for the application of EB.The temperature distribution of a floating zone melting in electron beam is calculated on the basis of a heat flow model; ЖC36 single crystal superalloy is remelted in ESZ 1.5/5 EB surface. Under the condition of power suddenly becoming zero , the diverse microstructure of ЖC36 single crystal superalloy is gotten. During the all experiments, the power is basicly invariable, but the zone melting rate is from 0.1mm/min to 6.0mm/min.The microstructures of ЖC36 single crystal superalloy are analyzed and detected with optical microscope , SENL EPA and XRD. The main conclusions are summarized as follows:(l)The temperature distribution of a floating zone melting in electron beam is calculated on the basis of a heat flow model.I If the length of melted zone is thought invariable for a given kind of alloy, the temperature gradient increases with the rising of the EB power and zone melting rate.II For a certain alloy, if the zone melting is smooth, the temperature gradient can be considered as constant.III The results demonstrate that the calculated temperature gradient is similar with the value evaluated by constituent supercooling theory. The temperature gradient of the ESZ1.5/5 EB apparatus is about 350K/cm for the ЖC36 single crystal superalloy.(2) If the zone melting power is basic unchangeable, the interface morphology of ЖC36 single crystal superalloy evolves from plan to cell and then to dendrite with the melting rate increasing. The gamma’ in the dendrite trucks aresmaller and more regular than those in the inter-dendrite area. Al, Ti, Mo are enriched elements in the inter-dendrite area, but W> Co are rich in the dendrite trunks. With the increasing of the melting rate, microsegregation increases and then decreases; Meanwhile, the size of gamma/gamma’ eutectics decreases.(3) The deviation of [100] orientation from the axial direction is within 10?for single crystals with various solidified morphologies.It can be concluded that the ЖC36 single crystal superalloy can be gotten with the EB apparatus with high temperature gradient.更多还原