عنوان مقاله [English]
The hot deformation behavior of materials has considerable complexity due to its dependence on the strain, strain rate, and temperature changes. Therefore, the prediction of material behavior is very important in these conditions. Various constitutive equations have been developed to predict the deformation behavior of materials at elevated temperatures, one of the most important of which is the Johnson-Cook equation. To develop a suitable constitutive equation that can accurately predict the behavior of the material, various tests such as tensile, compressive, and torsion tests are used. Due to the lack of frictional limitation, the torsion test can apply much higher deformation or strain than the compression and/or tensile tests. Therefore, in this study, the hot working behavior of 304 austenitic stainless steel was investigated using the hot torsion test and the Johnson-Cook constitutive equation was developed for it. For this purpose, experiments have been performed at the temperature range of 800-1000 ̊C and strain rate of 0.001-1 s-1 and high strain up to about 3. The results showed that flow stress decreases significantly with increasing temperature and decreasing strain rate. In places where the strain is sufficiently applied and the deformation temperature is high, dynamic recrystallization is observed in the microstructure while due to the strain difference along the sample radius, the microstructure of the deformed part is not nuniform along the radius. The developed Johnson-Cook equation was compared with the experimental results which were observed to have acceptable accuracy in predicting the hot deformation behavior of the studied steel.