An innovative annealing treatment method and its mechanism to refine deformed mixed grains of initial aged GH4169 superalloy
An innovative annealing treatment method and its mechanism to refine deformed mixed grains of initial aged GH4169 superalloy
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DOI：
10.1016/j.jallcom.2022.164325
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发表时间：
2022-03-14
影响因子：
6.2
通讯作者：
Chen, Quan
中科院分区：
文献类型：
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作者：
Chen, Ming-Song;Ma, Yan-Yong;Chen, Quan
GH4169合金在初始时效状态下的变形混合晶需要通过退火处理来细化。而对于等温退火处理，由于形核率的提高需要提高温度，而晶粒生长率的降低需要降低温度，变形后的混合晶粒只能细化到10 μ m左右。本文提出了一种新的方法，包括时效处理和随后的连续冷却再结晶退火处理（CC-RAT）。这种方法不仅可以提高形核速率，而且可以降低晶粒生长速率。研究了热处理工艺参数对显微组织的影响。此外，晶粒细化机制进行了研究，使用一个发展的元胞自动机（CA）模型。结果表明，时效过程中再结晶缓慢，析出大量δ相。在随后的CC-RAT中，提高起始温度（Ts）、降低冷却速率（V）或终止温度（T-e）可以显著促进再结晶，从而细化晶粒组织。这是由于提高了再结晶形核速率，有效地控制了晶粒长大速率。在CC-RAT的早期阶段，δ相阻碍了先形核的再结晶晶粒的快速长大。T-s的增加加速了形核速率，V的减小缩短了形核时间。两者都促进了新的再结晶核心的快速形成，特别是在δ相边界处。随着退火温度的降低，新生晶粒生长缓慢，并且这些新生晶粒限制了先形核的晶粒的生长。因此，获得了平均晶粒尺寸为5.82 μ m的细而均匀的显微组织。但当T-s过高或维斯过低时，会出现粗大的再结晶晶粒。因此，得出可行的工艺为：时效处理（900？x12 h），然后是CC-RAT（T-s = 990-1010？，V = 1-2？/ min，T_e = 950-970 μ m。(C) 2022 Elsevier B. V.保留所有权利。
The deformed mixed grains of the initial aged GH4169 superalloy need to be refined by annealing treatment. However, for the isothermal annealing treatment, the deformed mixed grains can only be refined to about 10 mu m because the increase of nucleation rate needs to increase the temperature while the decrease of grain growth rate requires to decrease temperature. In the paper, an innovative method including an aging treatment and a subsequent continuous-cooling recrystallization annealing treatment (CC-RAT) is proposed. This method can not only increase the nucleation rate but decrease the grain growth rate. The effects of heat treatment parameters on microstructure are investigated. Besides, the grain refinement mechanism is studied using a developed cellular automaton (CA) model. The results show that the recrystallization takes place slowly during aging, while large number of delta precipitates appear. In subsequent CC-RAT, increasing starting temperature (T-s), decreasing cooling rate (V) or ending temperature (T-e) can remarkably promote recrystallization, thereby refining grain microstructure. This attributes to the increase of re-crystallization nucleation rate and the effective control of grain growth rate. In the early stage of CC-RAT, delta precipitates hinder the quick growth of recrystallized grains nucleated firstly. Moreover, the increase of T-s accelerates the nucleation rate, and the decrease of V prolongs the time for nucleation. Both of them promote the rapid formation of new recrystallized nuclei, especially at delta phase boundaries. As the annealing temperature decreases, newborn grains grow slowly, and these new grains restrict the growth of grains nucleated first. Therefore, a fine and uniform microstructure with an average grain size of 5.82 mu m is obtained. However, when T-s is too high or Vis too low, some coarse recrystallized grains appear. Hence, the feasible process is concluded as follows: aging treatment (900 ?x12 h), followed by CC-RAT (T-s = 990-1010 ?, V = 1-2 ?/min, T-e & nbsp;= 950-970 ?. (C)& nbsp;2022 Elsevier B.V. All rights reserved.