镍基变形高温合金中g′ 相的多尺度分布行为及其对热变形性能的影响

Multimodal distribution of g′ phase and effect on hot deformation in a wrought nickel base superalloy

摘要:

本文主要研究了镍基变形高温合金在不同热处理过程中g′相的析出、形貌、尺寸及分布行为。通过扫描电镜观察分析高温固溶热处理后连续冷却、中断固溶冷却以及等温时效淬火后的组织构成。研究结果表明，固溶处理后连续冷去过程中，当冷却速率较高时，二次g′尺寸大小均匀，呈现单峰分布，随着冷却速率降低，二次g′尺寸增加，逐渐聚集长大并呈现花状形貌；当等温时效过程中二次g′周围过冷度重新建立，随后淬火过程中会产生三次g′，三次g′与二次g′构成双峰分布。在此基础上，探讨了g′相析出及演化对合金热变形行为的影响。

关键词:变形高温合金; γ";相; 热处理; 热变形

Abstract:

The microstructural evolution of different generations of ?′ precipitates during various heat treatment processes of a nickel base superalloy has been investigated. After solutionizing in the single ? phase field, continuous cooling, interrupted cooling and isothermal annealing tests were performed and characterization of the precipitates was carried out by scanning electron microscopy. It is found that a monomodal size distribution of the secondary ?′ precipitates can be achieved at a very high cooling rate in the continuous cooling process. With the decrease of the cooling rate, the secondary ?′ precipitates grow gradually and gather together to form a flowery morphology. When the secondary supersaturation is developed in the vicinity of the secondary ?′ precipitates during isothermal annealing, the water-quenched tertiary ?′ precipitates are produced and result in a bimodal size distribution of ?′ precipitates with the larger secondary precipitates. Furthermore, the effects of the secondary ?′ particle growth on the hot deformation are also discussed.

Key words:wrought superalloy, ?g′ precipitate, heat treatment, hot deformation