Abstract This work quantified nonuniform creep deformation across the heterogeneous heat-affected zone (HAZ) of Grade 91 steel with sophisticated experiments, including an electric-thermal finite element model–assisted Gleeble thermomechanical simulation and a high-temperature creep testing with in situ digital image correlation (DIC). High temperature creep properties of HAZ sub-zones were quantitatively measured by the DIC. By utilizing peak temperature, hardness, local creep strain, and underlying microstructures, creep deformation mechanisms in HAZ were further understood. DIC measurements reveal a creep-vulnerable zone (CVZ) exposed to a peak temperature of 932°C (close to AC3) in the intercritical HAZ experienced the fastest creep strength degradation instead of the soft zone with the lowest hardness prior to creep. The significantly reduced precipitation strengthening from misplacement of undissolved and coarsened M23C6 carbides led to a faster recrystallization of tempered martensite in the CVZ. Weak untransformed tempered martensite (ferrite grains) stabilized by local Cr enrichment from dissolved M23C6 also harmed the CVZ's creep resistance.

中文翻译：

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原位实验阐明9Cr钢热影响区蠕变变形机制

摘要 这项工作通过复杂的实验，包括电热有限元模型辅助的 Gleeble 热机械模拟和具有原位数字图像的高温蠕变测试，量化了 91 级钢的异质热影响区 (HAZ) 上的非均匀蠕变变形。相关性（DIC）。HAZ 子区的高温蠕变特性由 DIC 定量测量。通过利用峰值温度、硬度、局部蠕变应变和潜在的微观结构，进一步了解热影响区的蠕变变形机制。DIC 测量显示，临界 HAZ 中暴露于 932°C（接近 AC3）峰值温度的蠕变脆弱区 (CVZ) 经历了最快的蠕变强度退化，而不是蠕变前硬度最低的软区。未溶解和粗化的 M23C6 碳化物错位导致的析出强化显着降低，导致 CVZ 中回火马氏体的再结晶更快。由溶解的 M23C6 的局部 Cr 富集稳定的弱未转变回火马氏体（铁素体晶粒）也损害了 CVZ 的抗蠕变性。