The effect of high temperature plastic deformation on the dislocation slip rate of A588 Grade K weathering steel was analyzed in this study. The weathering steel was subjected to hot deformation at temperatures ranging from 900 to 1200°C with strain rates ranging from 0.001 to 1 s−1. The dislocation slip rate was analyzed by examining the microstructure and mechanical properties of the hot-deformed steel.
The results of the study showed that the dislocation slip rate of the A588 Grade K weathering steel increased significantly with increasing deformation temperature and strain rate. At lower deformation temperatures (below 1000°C), the dislocation slip rate increased linearly with increasing strain rate. However, at higher deformation temperatures (above 1000°C), the dislocation slip rate showed an exponential increase with increasing strain rate.
The increase in dislocation slip rate with increasing deformation temperature and strain rate was associated with the dynamic recrystallization and grain growth that occurred during hot deformation. The dynamic recrystallization process leads to the formation of new grains with a higher dislocation density, which in turn contributes to an increase in dislocation slip rate.
In addition, the increase in dislocation slip rate was also attributed to the softening effect of dynamic recrystallization, which reduced the resistance to dislocation motion. The enhanced dislocation slip rate resulted in a decrease in the yield strength and an increase in the elongation of the hot-deformed steel.
However, the increase in dislocation slip rate was not unlimited. At very high strain rates, the dislocation density became saturated because of the limited availability of mobile dislocations. As a result, the dislocation slip rate reached a maximum value and then plateaued with further increase in the strain rate.
Furthermore, the analysis of the deformation microstructure revealed that as the deformation temperature increased from 900 to 1200°C, the steel underwent a transition from dynamic recrystallization-dominated deformation to grain growth-dominated deformation. The grain size of the hot-deformed steel increased significantly with increasing deformation temperature, indicating that grain growth played a dominant role in deformation at higher temperatures.
The increase in grain size was attributed to the increased diffusivity of the alloying elements, which facilitated grain boundary migration and thus promoted grain growth. However, the growth in grain size was also accompanied by a decrease in the dislocation density, which reduced the dislocation slip rate.
Overall, the results of this study demonstrate that high temperature plastic deformation can significantly affect the dislocation slip rate of A588 Grade K weathering steel. The analysis showed that the dislocation slip rate increased with increasing deformation temperature and strain rate, which was attributed to the dynamic recrystallization and grain growth that occurred during hot deformation. The increase in dislocation slip rate resulted in a decrease in the yield strength and an increase in the elongation of the hot-deformed steel. However, the increase in dislocation slip rate was limited by the availability of mobile dislocations at very high strain rates. Thus, the findings of this study can provide a useful guideline for the design and optimization of high temperature plastic deformation processes for weathering steels.
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