In this study, the deformation-mechanism-based true-stress (DMTS) creep model is modified to include oxidation influence on the long-term creep performance of modified 9Cr-1Mo steels. An area-deduction method is introduced to evaluate oxide scale formation on the creep coupons, which is incorporated into the DMTS model formulated based on intragranular dislocation glide (IDG), intragranular dislocation climb (IDC), and grain boundary sliding (GBS) mechanisms, in modifying the true stress. Thus, the modified DMTS model can not only describe the creep curve, but also predict the long-term creep life and failure mode, which is shown to be in good agreement with the creep data generated in the authors’ laboratory as well as by the National Institute for Materials Science (NIMS) of Japan for long-term (> 10⁴ hours) creep life prediction on Grade 91 steels. In particular, the predictability of the model is demonstrated in comparison with the Larson–Miller parameter method. In addition, the modified DMTS model provides quantitative information of mechanism partitioning, insinuating the failure mode via intragranular/intergranular deformation. Therefore, it has advantages over the empirical models in providing physical insights of creep failure, which can be useful to material design for performance optimization.

中文翻译：

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改性9Cr-1Mo钢的氧化蠕变性能建模

在这项研究中，修改了基于变形机制的真实应力（DMTS）蠕变模型，以包括氧化对改性9Cr-1Mo钢的长期蠕变性能的影响。引入面积减小方法来评估蠕变试样上的氧化皮形成，并将其纳入基于颗粒内位错滑移（IDG），颗粒内位错爬升（IDC）和晶界滑动（GBS）机制制定的DMTS模型中，在改变真正的压力。因此，改进的DMTS模型不仅可以描述蠕变曲线，而且可以预测长期蠕变寿命和破坏模式，这与作者实验室以及实验室产生的蠕变数据非常吻合。日本国立材料科学研究所（NIMS）长期（> 10 ⁴小时）在91级钢上的蠕变寿命预测。特别是，与Larson-Miller参数方法相比，该模型的可预测性得到了证明。此外，改进的DMTS模型提供了机理划分的定量信息，通过晶内/晶间变形来暗示失效模式。因此，在提供蠕变破坏的物理见解方面，它与经验模型相比具有优势，这对于材料设计以优化性能非常有用。