In this work, simulated CGHAZ of T23 steel was produced via a thermomechanical simulator, and then the CGHAZ specimens were aged at 650 °C for 0 to 240 hours to simulate the microstructure evolution of as-welded CGHAZ during service. Microstructure change and carbide precipitation were observed by OM, SEM, EBSD and TEM + EDS. Carbide precipitation kinetics in T23 steel at 650 °C was calculated for comparison with the experiment results. The hardness change of CGHAZ during aging was detected, and the effect of microstructure evolution on hardness was analyzed. The results showed that the CGHAZ of T23 steel exhibited a mixed microstructure of martensite and bainite with high hardness in as-welded condition. After aging at 650 °C, the microstructure recovered, recrystallization occurred, the dislocation density decreased, and the lath width increased. Consequently, the hardness dropped, the drop depending on the aging time. In the early stage of aging (before 24 hours), the precipitations inside the grain were mainly M₃C, M₇C₃ and a small number of M₂₃C₆ carbides, while the precipitation at the grain boundaries was M₂₃C₆. The precipitation of M₂₃C₆ caused the hardness to drop rapidly. When aged for 24 to 48 hours, MX precipitated inside grains extensively. The precipitation hardening produced by MX could slow down the decline of hardness. As the aging proceeded, carbide precipitated and transformed as follows: M₃C → M₃C + M₇C₃ + M₂₃C₆ → M₃C + M₇C₃ + M₂₃C₆ + MX → M₂₃C₆ + MX + M₆C. W-rich carbides precipitated in some grain boundaries of CGHAZ during aging, which may be related to the W segregation at those grain boundaries.

中文翻译：

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T23钢时效过程中粗粒热影响区模拟组织的演变

在这项工作中，通过以下方式生产了T23钢的模拟CGHAZ：热力学模拟器，然后将CGHAZ标本在650°C下老化0至240小时，以模拟焊接过程中CGHAZ的微观结构演变。通过OM，SEM，EBSD和TEM + EDS观察到显微组织变化和碳化物沉淀。计算了T23钢在650°C下的碳化物析出动力学，以与实验结果进行比较。检测了CGHAZ合金在时效过程中的硬度变化，并分析了组织演变对硬度的影响。结果表明，T23钢的CGHAZ在焊接状态下呈现出高硬度的马氏体和贝氏体的混合组织。在650°C时效后，组织恢复，发生重结晶，位错密度降低，板条宽度增加。结果，硬度下降，下降的时间取决于老化时间。在熟化的早期（24小时之前），谷物内部的降水主要是M。₃ C，M ₇ C ₃和少量的M ₂₃ C ₆碳化物，而晶界处的沉淀为M ₂₃ C ₆。M ₂₃ C ₆的沉淀使硬度迅速下降。老化24至48小时后，MX大量沉淀在谷物内部。MX产生的沉淀硬化可以减慢硬度的下降。随着时效的进行，碳化物按如下方式沉淀和转变：M ₃ C→M ₃ C + M ₇ C ₃  + M ₂₃ C ₆  →M ₃ C + M₇ C ₃  + M ₂₃ C ₆  + MX→M ₂₃ C ₆  + MX + M _6C。富C的碳化物在时效过程中析出在CGHAZ的某些晶界中，这可能与W在这些晶界处的偏析有关。