原位观察镍基高温合金CMSX-4缩松形成过程及机理研究

In-situ Observation of Shrinkage Formation and Mechanism during Ni-based Superalloy Solidification

摘要:

采用共聚焦激光扫描显微镜(CLSM)对镍基单晶高温合金CMSX-4的凝固行为进行实时观察。并利用扫描电镜(SEM)和能谱仪(EDS)对凝固样品的微观形貌和元素偏析特性进行研究。在合金凝固过程中观察到缩松和碳化物的形成。缩松具有有三种形态：方形缩松,五角星形缩松和角形缩松。并讨论了三种缩松的形成机理,缩松的形成机制主要与次级枝晶臂沿不同方向生长所包围的封闭区域的形状有关。另外,发现碳化物由两种形式组成,即絮状碳化物和板条状碳化物。絮状碳化物中富含Hf元素,而Cr元素被富集在板条状碳化物。

Abstract:

Confocal laser scanning microscope(CLSM) was used to observe the solidification behavior of Nickel-based single crystal superalloy CMSX-4 in real time. SEM and EDS were used to study the micromorphology and element segregation characteristics of the solidified samples. Shrinkage and carbide formation were observed during alloy solidification. There are three types of shrinkages: square shrinkages, pentagonal star shrinkages and angular shrinkages. The formation mechanism of the three shrinkages is disccused, which is mainly related to the shape of the enclosed area surrounded by the secondary dendrite arms growing in different directions. In addition, carbides are found to be composed of two forms, namely flocculent carbide and lath carbide. Hf elements are enriched in flocculent carbides, while Cr elements are enriched in lath carbides.