Effect of Warm Deformation on Mechanical Properties and Deformation Mechanism of Nano/Ultrafine‐Grained 304 Stainless Steel

Abstract

To prevent the performance of 304 stainless steel with nano/ultrafine grain from being damaged during cold forming, the deformation temperature is increased to above the Md point, and its mechanical properties and deformation mechanism during warm forming are studied. The significant effects of rolling temperature on the microstructural evolution of nano/ultrafine‐grained 304 stainless steel deformation are characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy, and the relationships between temperature, stacking fault energy (SFE), and deformation mechanisms are discussed. The results show that the tensile strength of 304 austenitic stainless steel decreases with an increase in the tensile temperature from room temperature to 900 °C, and the total elongation decreases first with increasing temperature. The elongation at 400 °C is the worst, only 32%. The dislocation slip becomes the only deformation mechanism due to the high SFE. Then, the total elongation begins to increase, and the highest elongation is 288% at 800 °C, showing superplastic behavior and the deformation mechanism is dynamic recrystallization, and grain boundary sliding.