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利用Thermo-Calc、DICTRA软件及其数据库,建立碳化物长大-Cr原子扩散模型,进行镍基690合金晶界贫Cr区演变的动力学模拟研究,并与扫描透射电子显微分析和能谱分析技术得到的合金晶界Cr含量实测值相比较,验证模型的合理性。结果表明:600~800℃敏化温度范围内进行等温处理时,敏化初期M23C6颗粒长大速度快,尺寸迅速增大;一定时间后长大速度急剧下降,尺寸增速减缓直至M23C6颗粒达到稳定的尺寸。等温条件下晶界Cr含量变化与敏化时间密切相关,敏化初期碳化物快速长大是影响晶界附近最低Cr含量的主要原因;而随着敏化时间延长,晶内Cr原子向贫Cr区的扩散愈加充分,贫Cr区最低Cr含量逐渐提高。该模型计算得到的晶界附近最低Cr含量值接近实测值,该模型可准确预测不同敏化过程中的晶界附近最低Cr含量。
Using the Thermo-Calc and DICTRA software and their databases, a model of carbide growth-Cr atom diffusion was established to simulate the evolution of Cr-depleted regions in the grain boundary of Ni-based 690 alloy. The results were compared with scanning transmission electron microscopy Analysis of alloy grain boundaries obtained by Cr measured values compared to verify the rationality of the model. The results showed that the M23C6 particles grew rapidly at the initial sensitization temperature and rapidly increased in size at the sensitization temperature range of 600 ~ 800 ℃. After a certain period of time, the growth speed decreased sharply and the size growth slowed down until the M23C6 particles reached a steady state size of. The change of Cr content in the grain boundary under isothermal condition is closely related to the sensitization time. The rapid growth of carbides in the early stage of sensitization is the main reason that affects the minimum Cr content near the grain boundary. With the increase of sensitization time, District spread more fully, the lowest Cr content of lean Cr area gradually increased. The lowest Cr content in the vicinity of the grain boundary calculated by this model is close to the measured value. This model can accurately predict the minimum Cr content near grain boundaries in different sensitization processes.