Through a series of thermal-mechanical processing (TMP) routes with various ratios of cold rolling and subsequent high-temperature annealing, the samples with different critical strain states were prepared to explore the evolution of grain boundary character distribution (GBCD) in INCOLOY 925 during grain boundary engineering (GBE). The GBE microstructure was characterized using the electron backscatter diffraction to study the influence of TMP parameters on the evolution of GBCD and the penetration of random high angle grain boundaries. The results show that the different states of pre-strain correspond to the variational formation mechanism of grain boundary network (GBN). The strain induced boundary migration is the predominant mechanism with the rolling reduction lower than critical strain. With the slight increase of strain, the recrystallization nucleation can be initiated to generate the strain-free grains at a certain annealing temperature. Moderate strain is needed to ensure adequate growth for twin related domains (TRDs). Besides, with the increase of strain and temperature, the dominant mechanism of GBCD gradually transfers from the new twinning mechanism to the Σ3 regeneration mechanism. Specifically, the TMP sample with 10% rolling reduction followed by annealing at 1075 °C for 10min shows relatively higher grain size difference ratio and average grains numbers in the TRDs, indicating that a larger initial grain size can increase critical strain and delay the nucleation of strain-free grains during TMP treatment. The moderately higher grain size shows an opposite effect on the formation of GBN. Finally, an estimation model of critical strain, as a function of initial grain size and annealing temperature, was constructed based on the artificial neural network, and the predicted results show a high consistency with the actual microstructure evolution.

通过一系列具有不同冷轧比和后续高温退火的热机械加工 (TMP) 路线，制备了具有不同临界应变状态的样品，以探索 INCOLOY 925 在过程中晶界特征分布 (GBCD) 的演变。晶界工程（GBE）。采用电子背散射衍射表征GBE微观结构，研究TMP参数对GBCD演变和随机大角度晶界穿透的影响。结果表明，预应变的不同状态对应于晶界网络（GBN）的变分形成机制。应变诱导的边界迁移是压下率低于临界应变的主要机制。随着应变的轻微增加，在一定的退火温度下，可以引发再结晶形核，生成无应变晶粒。需要适度的应变来确保孪生相关域 (TRD) 的充分生长。此外，随着应变和温度的升高，GBCD的主导机制逐渐从新的孪生机制转变为Σ3再生机制。具体而言，压下量为 10% 并在 1075 ℃退火 10 分钟的 TMP 样品在 TRD 中显示出相对较高的晶粒尺寸差异率和平均晶粒数，表明较大的初始晶粒尺寸可以增加临界应变并延迟形核的形核。 TMP 处理过程中的无应变晶粒。适度较高的晶粒尺寸对 GBN 的形成显示出相反的影响。最后，临界应变的估计模型，