Influence of Aging Treatment on Microstructure and Tensile Properties of a Hot Deformed UNS S32750 Super Duplex Stainless Steel (SDSS) Alloy

Abstract

In this present study, the influence of isothermal aging temperature and duration on microstructural and mechanical properties of a hot-deformed UNS S32750 super duplex stainless steel (SDSS) alloy was investigated by SEM-EBSD (scanning electron microscopy-electron backscatter diffraction) and tensile testing techniques. An isothermal aging treatment, at temperatures between 400 and 600 °C and treatment duration between 3 and 120 h, was applied to a commercial UNS S32750 SDSS alloy. Microstructural characteristics of all thermomechanical (TM) processed states, such as distribution and morphology of constituent phases, grain’s modal orientation (MO), and obtained mechanical properties were analysed correlated with the TM processing conditions. The obtained experimental results show that the constituent phases, in all TM processed states, are represented by elongated γ-phase grains within the δ-phase matrix. The R-phase was observed in the case of aging treatment performed at 600 °C for 120 h. Within the δ-phase matrix, dynamically recrystallized grains were identified as a result of applying hot deformation and isothermal aging treatments. Also, it was observed that aging treatment parameters can significantly influence the mechanical behaviour exhibited by the UNS S32750 SDSS alloy, in terms of elongation to fracture and absorbed energy during impact testing.

Effect of thermal ageing on microstructure, mechanical properties, and fracture behaviour of 50 % cold rolled duplex stainless steel (alloy 2507)

“…So, considering the 1040 °C solution annealing temperature and ageing temperature variation, with an increasing temperature from 950 °C to 1050 °C, yield strength and ultimate tensile strength decrease, and correspondingly, total elongation and product of strength and elongation values are increased, Table 3. It indicates that higher ageing temperature increases the release of the stored energy during the cold working and thereby leads to an enhanced ductility, a better combination of strength and ductility but a decrease in the strength which is suited for formability applications [5, 11, 14]. Similar trends were evident for the samples that underwent various processing after hot deformation and solution treatment at 1300 °C.…”

“…Further addition of nitrogen improves weldability and slows down the formation of intermetallic phases, due to its austenite stabilizing characteristics, it maintains a proper ferritic and austenitic balance and improves the corrosion resistance [1, 12–14]. In addition, nitrogen provides structural hardening via interstitial solid solution strengthening and increases yield strength and ultimate tensile strength without altering the toughness [2, 7, 11].…”

“…The effects of high‐temperature ageing of duplex stainless steels were reported [2]. The results of ageing and cold deformation on the duplex stainless steels were studied earlier [7–11, 14–15, 17–18, 28–32]. However, the effects of heat treatment, deformation on microstructure, mechanical properties, and fracture behaviour need a systematic investigation for improvement in mechanical properties, which are rarely found in the literature.…”

Quantitative Description of the Microstructure of Duplex Stainless Steels Using Selective Etching

“…The properties of duplex stainless steels (DSSs) depend on the ferrite-austenite ratio and on the contents of secondary phases [1]. The actual phase content depends on the chemical composition of the steel, and heat treatment of the final product [2]. Therefore, it is necessary to control the volume fractions, morphologies, and distribution patterns of all phases.…”

Strength Enhancement of Superduplex Stainless Steel Using Thermomechanical Processing

“…It was shown that the two most influential occurring phenomena are represented by the stress relief and the secondary phase precipitation. In the second one [10], the effect of controlled cold rolling on the microstructure and mechanical properties of the rare earth Ce-modified superduplex stainless steel was investigated. It is shown that with the increase in deformation, the strength of Ce-modified superduplex stainless steel increases rapidly and the elongation decreases dramatically.…”