Abstract
The deformation behavior for highly purified Fe-17Cr alloy was investigated at 700~1000 °C and 0.5~10 s−1. The microstructure evolution and corresponding mechanism during deformation were studied in-depth, using electron backscattering diffraction, transmission electron microscopy and precession electron diffraction. During deformation, dynamic recrystallization (DRX) occurred, along with extensive dynamic recovery, and the active DRX mechanism depended on deformation conditions. At higher Zener-Hollomon parameter (Z ≥ 5.93 × 1027 s−1), the development of the shear band was promoted, and then continuous DRX was induced by the formation and intersection shear band. At lower Zener-Hollomon parameter (Z ≤ 3.10 × 1025 s−1), the nucleation of the new grain was attributed to the combination of continuous DRX by uniform increase in misorientation between subgrains and discontinuous DRX by grain boundary bulging, and with increasing temperature, the effect of the former became weaker, whereas the effect of the latter became stronger. The DRX grain size increased with the temperature. For alleviating ridging, it seems advantageous to activate the continuous DRX induced by shear band through hot deformation with higher Z. In addition, the modified Johnson-Cook and Arrhenius-type models by conventional way were developed, and the modified Johnson-Cook model was developed, using the proposed way, by considering strain dependency of the material parameters. The Arrhenius-type model was also modified by using the proposed way, through distinguishing stress levels for acquiring partial parameter and through employing peak stress to determine the activation energy and considering strain dependency of only other parameters for compensating strain. According to our comparative analyses, the modified Arrhenius-type model by the proposed approach, which is suggested to model hot-deformation behavior for metals having only ferrite, could offer a more accurate prediction of flow behavior as compared to other developed models.
Highlights
IntroductionFe-Cr alloys generally exhibit low formability and poor surface quality
Deformation temperature has a significant effect on strain-rate sensitivity, and as temperature lowers, strain-rate sensitivity reduces, which can be explained in terms of the stacking fault energy
(2) During deformation, dynamic recrystallization occurs alongside extensive dynamic recovery, and the nucleation mechanisms of new grains can be considered as a function of deformation conditions
Summary
Fe-Cr alloys generally exhibit low formability and poor surface quality. Improving these shortcomings for Fe-Cr alloys has been attempted by controlling rolling process [3,4,5,6,7,8,9]. Introducing the warm-rolling process is the effective way to increase the intensity or uniformity of γ-fiber recrystallization texture, obtain a more homogeneous distribution of oriented grain colonies in the final sheet, and eventually increase the r-value and weaken the occurrence of ridging by enhancing grain fragmentation and grain interior nucleation and refining hot-rolled and annealed microstructure. Dynamic recrystallization (DRX) holds great promise for controlling and refining the microstructure and thereby improving the r-value and alleviating ridging [10,11,12]. To further optimize the warmrolling process, the systematic investigation of flow behavior and microstructure evolution, especially DRX behavior during warm deformation, is necessary
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