不同冷速下GH4169高温合金凝固过程的原位观察

In-situ Observation of Solidification Process of GH4169 Superalloy at Different Cooling Rates

利用带有红外加热炉的共聚焦激光扫描显微镜对GH4169高温合金在冷速分别为5,50,200K·min^(-1)条件下的凝固过程进行了原位观察,并通过图形处理软件计算了自由表面固相含量随温度及时间的变化关系;用光学显微镜观察了各冷速下高温合金的凝固组织,计算了合金凝固后的二次枝晶间距。结果表明:GH4169高温合金在凝固过程中随着温度的降低,枝晶不断生长,新核不断形成;随着冷速的增加,枝晶组织明显细化;固液转变依次经历初始平缓增加段、稳定快速增长段、残液转变减慢段三个阶段,冷速的增加致使合金凝固后显微组织的二次枝晶间距减小,偏析相更为均匀细小。

The solidification process of the GH4169 superalloy was in-situ observed at the cooling rate of 5, 50, 200 K · min-1 by means of confocal laser scanning microscopy combined with an infrared image furnace. The variation of solid phase content at the free surface and temperature as well as time was calculated by image process software. Using optical microscopy to observe the solid microstructure of the superalloy cooled at different rates, the secondary dendrite arm spacing of the alloy cooled at different rates was calculated. The results show that with the decrease of temperature during the GH4169 superalloy solidification process, the dendrite grew continuously and the new nucleation formed. The dendrite structure refined obviously with increasing the cooling rate. The transformation process of solid to liquid was in order of initial stable increasing stage, stable and rapid growth stage and residual liquid transformation stage. The increase of cooling rate led to the decrease of secondary dendrite arm spacing after solidification, and the precipitates got more uniform and fine.