摘要
当激光熔池内的柱状枝晶沿着熔池边界外延生长时,其方向并不严格平行于温度梯度,而是选择与基体一致的择优方向生长,因此基体取向可以影响柱状晶的外延生长行为。在使用激光金属成型/沉积技术修复昂贵的单晶部件时,需要考虑这一特性。现有研究已经实现了(001)晶面上的柱状晶完全外延生长进而获得完整单晶。然而由于叶片形状复杂,实际修复过程中可能会遇到的不同取向表面。论文对(001)和非(001)取向表面修复过程中的杂晶形成能力进行了比较研究,通过数值计算获得了控制微观组织的局部凝固变量,并将杂晶晶粒的体积分数作为量化单晶完整性指数。结果表明,与(001)晶面相比,多数非(001)晶面可以促进柱状晶的外延生长,进而获得更好的单晶完整性,实验结果也验证了这一结论。分析显示不同枝晶生长区域的边界是杂晶形成敏感区,两种晶面的差异在于边界数目及其位置。研究结果可以优化修复和制造应用中的沉积方向和激光加工窗口提供指导。
Epitaxial crystal in dendritic form grows along the crystallographic direction of a substrate and can be misoriented with respect to the heat flow direction.This point needs to be considered during the repair of valuable single crystal components with laser metal forming/deposition techniques.During the process,achieving epitaxial structures without nucleated grains is required to maintain single crystal integrity,which is achieved on(001)-oriented planes.However,randomly oriented surfaces can be encountered in real applications that need to be examined.In this work,the repairs on(001)-and non-(001)-oriented surfaces are studied comparatively,with a focus on the avoidance of nucleated grains.The local solidification variables that control the deposited structures are calculated,and the fraction of nucleated grains is quantified as an index of single-crystal integrity.The results show that enhanced epitaxial growth can be achieved on most non-(001)planes compared to the(001)surface,which is also verified by our experiments.This difference can be related to the boundaries of different dendritic growth regions as well as their locations.It is expected that the results can be applied to optimize deposition orientations and laser processing windows in repair and manufacturing applications.
作者
王雷
何峰
王志军
李俊杰
王锦程
WANG Lei;HE Feng;WANG Zhijun;LI Junjie;WANG Jincheng(State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China)
出处
《铸造技术》
CAS
2024年第3期288-292,共5页
Foundry Technology
基金
中央高校基本科研业务费专项资金
凝固技术国家重点实验室自主研究课题(2023-TS-01)
国家自然科学基金(52301063)。
关键词
单晶高温合金
激光修复
晶区分布
杂晶形成
single-crystal superalloy
laser repair
growth region distribution
stray grain formation
