Development and Validation of Processing Maps for Hot Deformation of Modified AISI 321 Austenitic Stainless Steel

Abstract

Hot deformation studies and optimization of hot working parameters and corresponding microstructure evolution were explored in a modified AISI 321 austenitic stainless steel. Hot compression tests were carried out in the temperature range of 800°C–1,100°C and five different strain rates (0.001–10 s−1). Processing maps were developed based on the results of hot compression tests, employing the principles of dynamic materials model and various domains of microstructure evolution were identified. The stable and unstable domains, as well as various domains indicating other microstructural reconstitutive mechanisms, including dynamic recrystallization (DRx), were identified with the aid of a processing map. The domain for DRx was confirmed by microstructural analysis of deformed specimens and also from the inflections in hardening curves. The processing regime for microstructural control was identified, and the results were validated by actual forging trials on a 1,000-T hydraulic forging press. The grain size of laboratory-tested hot-compressed samples and industrially forged billets exhibited excellent correlation. Constitutive equation for hot deformation was also developed for the steel based on hot compression test results.

Hot Deformation Behaviors of as Cast 321 Austenitic Stainless Steel

“…Ghazani et al [27] indicated that the critical damage value increases with the increase of deformation temperature and decrease of strain rate, and the lower the critical damage value, the higher is the risk of plastic fracture. The processing windows with the lowest fracture risk for 321 stainless steel are 0.001 s −1 , 1025-1075 • C, and 1150-1200 • C. The distribution flow instability zone in literature [15] is similar to that reported in this paper, but the safe processing temperature is lower at 900-1000 • C. The coarse-grained structure may be the reason because this is more dependent on high temperature than the finegrained structure. Therefore, the safe processing window of the tested steel is 1000-1200 • C and 0.01-0.1 s −1 .…”

“…Poliak et al [18] indicated that although DRX had occurred, there was no obvious peak stress on the flow curves. However, flow curves often show obvious softening for single-phase austenitic stainless steel [10,14,15]. This may be related to the existence of the δ phase because flow curves do not only reflect the work-hardening and dynamic softening behavior of single-phase austenite.…”

“…In addition, electron back-scatter diffraction (EBSD) results of microstructure evolution showed that the main softening process in the temperature range of 800-950 • C is DRV, and dynamic recrystallization DRX is the main softening mechanism at 1000-1200 • C [14]. Anoop et al [15] established the hot deformation constitutive equation of wrought 321 stainless steel and a processing map was drawn.…”

Influence of Higher Stabilization Temperatures on the Microstructure and Mechanical Properties of Austenitic Stainless Steel 08Ch18N10T

“…There is a particular lack of papers concerning non-commercial steel 08Ch18N10T according to GOST standards, developed especially for the needs of nuclear engineering, and which is subject to higher demands for its mechanical properties and micropurity. Some publications have also studied the deformation behavior of AISI321 steel [19][20][21][22], rolling or forging conditions and their effect on the strain hardening of 08Ch18N10T steel, or the course of solution and stabilization annealing [23]. It is known that these forming operations have a certain effect on the production process of the steel.…”