The transient creep deformation behavior and dislocation evolution in G115 steels were investigated in the temperature range 625–675 °C for applied stresses of 120–220 MPa. The transient creep curves showed that creep rate decreased with increases in time and creep strain. In this study, a novel method was proposed to determine the transient creep strain and the transient creep time. The strain decreased with increase in applied stress between 625 °C and 675 °C. A phenomenological constitutive equation was used to characterize the transient creep curves of G115 steels. The results showed that the constitutive equation for the G115 steel had a high precision. An internal stress was introduced to study the interactions of dislocations and precipitates, and a mechanism-based equation for transient creep in G115 steels was derived. The dependences of normalized strain and transient creep time on applied stress and temperature were analyzed in detail to better understand the transient creep deformation mechanism. It was concluded that dislocation annihilation at the grain boundaries was the dominant rate-controlling mechanism in the transient creep deformation of G115 steels. It was observed that the dislocation structures became more complex and no obvious textural features occurred after the transient creep deformation. The calculated dislocation density decreased at 650 °C relative to the initial value, which was mainly attributed to the annihilation processes occurring at the grain boundaries and the subsequent formation of subgrain boundaries.

研究了G115钢在625–675°C温度范围内施加120–220 MPa应力时的瞬态蠕变变形行为和位错演化。瞬态蠕变曲线表明，蠕变速率随时间和蠕变应变的增加而降低。在这项研究中，提出了一种确定瞬态蠕变应变和瞬态蠕变时间的新方法。应变在625°C至675°C之间随施加应力的增加而减小。现象学本构方程用于表征G115钢的瞬态蠕变曲线。结果表明，G115钢的本构方程具有较高的精度。引入内应力来研究位错与析出物的相互作用，并推导了基于机理的G115钢瞬态蠕变方程。详细分析了归一化应变和瞬态蠕变时间对施加应力和温度的依赖性，以更好地理解瞬态蠕变变形机理。得出的结论是，晶界处的位错an没是G115钢瞬态蠕变变形的主要速率控制机制。观察到，瞬时蠕变变形后，位错结构变得更加复杂，并且没有明显的纹理特征发生。相对于初始值，计算出的位错密度在650°C时降低，这主要归因于发生在晶界的an没过程以及随后形成的亚晶界。