Deformation Behaviour and Microstructural Evolution During Hot Compression of AISI 904L

Abstract

The hot deformation behaviour and microstructural evolution of AISI 904L super‐austenitic steel has been investigated by means of hot compression tests. The tests were carried out on a Gleeble 1500D thermo‐mechanical simulator in the temperature range from 850 °C to 1150 °C and at strain rates range from 0.001 s−1 to 5 s−1. The microstructure evolution was examined by means of light optical microscopy (LOM). The results show that after an initial deformation hardening, softening mechanisms occur. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener–Hollomon parameter in the hyperbolic‐sine equation with the activation energy for deformation of 463 kJ/mol. The steady state was achieved at maximum strain of 0.9 only at the lower strain rates (under 1 s−1) and the higher temperatures (above 1100 °C). Microstructural analyses showed a gradual increase in the dynamically recrystallized area with an increase of the temperature and a decrease of the strain rate. The grain size did change, as expected, correlating to the deformation conditions.

Constitutive equation and dynamic recrystallization behavior of as-cast 254SMO super-austenitic stainless steel

“…This signifies that the deformation mechanism is dominated by the DRX instead of diffusion or DRV. Combining with other austenitic stainless steels, such as 301, 304, 316, 317, and 904L steels [3,10,32,33], as shown in Fig. 4, there is no doubt that the Q value for hot deformation of as-cast 254SMO SASS is significantly high, indicating that the hot deformation for this alloy is rather difficult.…”

“…[8]) and the acceleration of recovery process [9]. Thus, the sluggish DRX could be observed in the SASSs [3,10]. In order to reveal the distinct hot workability for this class of materials, the investigation on the correlation between processing variables (temperature, T, strain rate, _ e, and strain, e are included) and microstructural evolution in the hot working becomes particularly significant.…”

“…Recently, super-austenitic stainless steel (SASS) has been received great attentions due to the favorable combination of high strength and toughness, good weldability and excellent resistance to pitting and crevice corrosion, all which enable its use in chemical, petrochemical, oceanic, nuclear, military and other demanding fields [1][2][3]. It can be said that, the development of SASS successfully provides a bridge between expensive nickel-based alloys and relatively cheap austenitic stainless steels [4].…”

Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel

“…Additions of these elements impart a remarkable improvement in oxidation resistance, microstructural stability and high temperature strength at elevated temperatures. Therefore, SASSs have been widely used as important structural materials for application in engineering fields such as chemical, petrochemical, oceanic, nuclear industries and so on in recent decades [1][2][3][4]6,7], it can be said that SASS applications successfully provide a bridge between cheap austenitic stainless steels and relatively expensive special superalloys [8].…”

“…As observed in past studies, a significant positive correlation of Cr, Ni and Mo elements has been found with the SFE in austenitic grades of stainless steels (e.g., 34 mJ· m −2 of AISI 305, 78 mJ· m −2 of AISI 316, 94 mJ· m −2 of AISI 310S and 164 mJ· m −2 of AISI 904L) [9,11]. Along with the increase in the SFE, steels are very susceptible to hot cracking during hot deformation, especially edge cracking due to the sluggishness of the dynamic recrystallization process (DRX) [7,12].…”