A Comparative Analysis of the Hot Working Behavior of AISI ۴۲۰ and AISI ۳۰۴ Stainless Steels Using the Hot Torsion Test

The complex nature of hot deformation in materials arises from their reliance on changes in strain, strain rate, and temperature. Consequently, accurately predicting material behavior under such conditions is of utmost importance. To accomplish this, various tests including tensile, compressive, and torsion tests are utilized. The torsion test, in particular, allows for higher levels of deformation or strain due to the absence of frictional limitations compared to compression and tensile tests. Therefore, this study investigates and compares the hot working behavior of AISI ۴۲۰ and AISI ۳۰۴ through the application of the hot torsion test. To carry out this investigation, experiments were carried out within a temperature range of ۸۰۰-۱۰۰۰ ̊C. Rotational speeds of ۰.۰۲۸, ۰.۲۸, ۲.۸, and ۲۸ radians per second were selected, enabling high rotation angles of up to approximately ۸۰ radians. Mechanical and microstructural analyses show a significant decrease in torque and flow stress when rising the temperature and proportionally decreasing the rotational speed. The flow stress and torque values of AISI ۳۰۴ stainless steel are consistently higher than those of AISI ۴۲۰ stainless steel across various strain rates and temperatures. Furthermore, when a sufficient strain is applied and the deformation temperature is high, dynamic recrystallization is observed in the microstructure. However, due to variations in strain across the radius of the sample, the microstructure of the deformed section appears to vary along the radial axis.

کلیدواژه ها:

Hot torsion ، AISI ۴۲۰ ، AISI ۳۰۴ ، Flow stress ، Microstructure