Coarsening kinetics of γ′ precipitates in a Re-containing Ni-based single crystal superalloy during long-term aging
Coarsening kinetics of γ′ precipitates in a Re-containing Ni-based single crystal superalloy during long-term aging
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含铼镍基单晶高温合金长期时效过程中γ'析出物的粗化动力学
DOI：
10.1016/j.jmst.2020.05.034
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发表时间：
2021-01-30
影响因子：
10.9
通讯作者：
Fu, Hengzhi
中科院分区：
文献类型：
--
作者：
Zhang, Jiachen;Liu, Lin;Fu, Hengzhi
研究了一种含Re的镍基单晶高温合金在900、950和1000 ℃等温时效过程中γ '相的形态演变和粗化动力学。热处理后，在实验合金中获得了具有低错配的轮廓分明的立方γ '沉淀物。然后根据100 ~ 2000 h不同时效时间下测得的析出物尺寸，计算并确定了γ '相的粗化速率常数和粒度分布（PSD）。时效2000 h后，γ '相在900 ℃时仍保持立方形状，而在950和1000 ℃时呈球形。为了使实验结果与理论分析相吻合，研究了基于r（3）与t的函数关系的扩散控制粗化模型（经典Lifshitz-Slyozov-瓦格纳粗化模型）和基于r（2）与t的函数关系的界面控制粗化模型（跨界面扩散控制粗化模型）。根据LSW模型，发现Re作为合金中扩散最慢的溶质，构成了粗化的限速步骤，而限制粗化的过程可能与Al通过γ/γ '界面的扩散有关。通过实验数据与LSW和TIDC模型预测值的比较，讨论了PSD和粗化指数。粗化机制可分为四种：（i）扩散控制粗化;（ii）扩散和界面共同控制粗化;（iii）界面控制粗化;（iv）界面控制粗化伴随γ '合并。(C)2020由Elsevier Ltd代表Journal of Materials Science & Technology编辑部出版。
The morphological evolution and coarsening kinetics of gamma' precipitates in a Re-containing Ni-based single crystal superalloy were investigated during isothermal aging at 900, 950 and 1000 degrees C. After heat treatment, well-defined cuboidal gamma' precipitates with low misfit was obtained within the experimental alloy. Then coarsening rate constants and particle size distribution (PSD) of gamma' phases were calculated and specified based on the measured precipitate sizes for varying periods of aging times from 100 to 2000 h. After aging for 2000 h, gamma' precipitates maintained cubical shape at 900 degrees C, while exhibited sphere at 950 and 1000 degrees C. Coarsening models based on diffusion-controlled process with a functional relationship of r(3) vs. t (classic Lifshitz-Slyozov-Wagner coarsening model) and interface-controlled model with a function of r(2) vs. t (trans-interface diffusion-controlled coarsening model) were investigated to fit between the experimental results and theoretical analysis. It was found that Re as the slowest diffusing solute in the alloy constituted the rate-limited step for coarsening based on LSW model, while the process limiting coarsening as governed by an interface diffusion process could possibly be related to the Al diffusion through the gamma/gamma' interface. The PSDs and coarsening exponent were discussed by comparing the experimental data with predictions of LSW and TIDC models. Finally, coarsening mechanism could be divided into four regimes: (i) coarsening by diffusion-controlled; (ii) coarsening by diffusion and interface co-controlled; (iii) coarsening by interface-controlled; (iv) coarsening by interface-controlled accompanied with gamma' coalescence. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.