Abstract
The features of discontinuous dynamic recrystallization (DRX) in a highly-alloyed austenitic stainless steel were studied at temperatures of 800 °C to 1100 °C. Hot deformation accompanied by DRX was characterized by an activation energy of 415 kJ/mol. The frequency of the sequential DRX cycles depended on the deformation conditions; and the largest fraction of DRX grains with small grain orientation spread below 1° was observed at a temperature of around 1000 °C and a strain rate of about 10−3 s−1. The following power law relationships were obtained for DRX grain size (DDRX) and dislocation density (ρ) vs. temperature-compensated strain rate (Z) or peak flow stress (σP): DDRX ~ Z−0.25, ρ ~ Z0.1, σP ~ DDRX−0.9, σP ~ ρ1.4. The latter, i.e., σP ~ ρ1.4, was valid in the flow stress range below 300 MPa and changed to σP ~ ρ0.5 on increasing the stress. The obtained dependencies suggest a unique power law function between the dislocation density and the DRX grain size with an exponent of −0.5.
Highlights
Hot working is a common treatment frequently applied to various structural steels and alloys
The aim of the present study was to investigate the features of discontinuous DRX during hot deformation of a highly-alloyed austenitic stainless steel, the chemical content of which is designed for low temperature applications
The power law relationships between the temperature-compensated strain rate (Z) and the flow stress as well as between Z and the DRX microstructures developed under hot working conditions allow us to relate the parameters of DRX microstructures to the flow stress
Summary
Hot working is a common treatment frequently applied to various structural steels and alloys. One of the most interesting and important phenomena accompanying thermomechanical treatment at elevated temperatures is dynamic recrystallization (DRX), which may result in desirable microstructure evolution providing the required combination of mechanical properties of the processed semi-products [1,2,3]. Depending on the type of metallic material, i.e., crystal lattice, impurity, alloying extent, stacking fault energy (SFE), phase content, etc., various mechanisms of DRX contribute to the final microstructure. Discontinuous DRX involving cyclic nucleation and growth of new DRX grains commonly develops during hot working of face-centered cubic metals and alloys with low-to-medium SFE. The mean grain size in discontinuously DRX microstructures depends on the deformation conditions, namely, temperature and strain rate, similar to the flow stress, and can be related to the flow stress or temperature-compensated strain rate through power law functions [3,4,5]. A decrease in temperature and/or increase in strain rate results in an increase in the flow stress while decreasing the DRX grain size
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
