Characterization of dislocation evolution during creep of 9Cr1Mo steel using internal friction measurement

Highlights: • The diffusion-controlled dislocations during creep of 9Cr-1Mo steel was successfully characterized using internal friction measurement. • It revealed that these diffusion-controlled dislocations are actually the immobile dislocations forming during creep. • The internal friction measurement offers a potential method to characterize the configuration of dislocations rather than mobile dislocations. -- Abstract: Using the internal friction measurement, this work dealt with the change of dislocation configuration during the creep of 9Cr1Mo steel at 873 K. At different creep times, specimens of this steel were firstly prepared by the interrupted test to simulate various creep states. Then, the internal friction of these specimens was measured by a dynamic mechanical analyzer (DMA) to characterize the dislocation configuration. Based on the analysis of internal friction results, it showed that both the density and distribution of diffusion-controlled dislocations vary continuously with creep time, and there has a density peak at the end of primary creep. Meanwhile, the kinetics of dislocation motions was introduced to study the evolution of dislocations during present creep in detail. In comparison with the calculated results, the movement mechanism of above diffusion-controlled dislocations was clarified successfully by the modeled dislocations. In addition, the present work offered a powerful tool to evaluate the configuration of dislocations rather than mobile dislocations.