Title : Effect of microstructure and texture on the evolution of mechanical properties in a cold rolled and annealed UNS S32101 lean duplex stainless steel sheet
Abstract:
In the present investigation, the effect of microstructure and texture on the evolution of mechanical properties during recrystallization for 80% unidirectionally cold rolled UNS S32101 lean duplex stainless steel (LDSS) sheet was investigated. Microstructures were observed using optical microscope (OM), scanning electron microscope (SEM) and electron backscattered diffraction (EBSD), while bulk texture was measured by X-ray Diffraction (XRD). Cold rolled samples showed Brass-type texture for austenite and strong α-fiber (RD//<110>) and γ-fiber (ND//<111>) for ferrite. Increase in cold rolling resulted in the formation of strain-induced martensite (a’, SIM) from austenite (g). However, with annealing, γ seems to increase as the process leads to reversing the effect of cold rolling i.e., reversion of a’ to g. The morphology of grains changed from lamellar to near globular with an increase in the annealing time. The texture intensity reduced after recrystallization for both austenite and ferrite. A sharp decrease in stored energy (275 kJ/m3 to 650 J/m3 (austenite) and 293 kJ/m3 to 520 J/m3 (ferrite)) and hardness was observed with increase in fraction recrystallized. Tensile properties and hardness were obtained for deformed and fully recrystallized samples. After annealing for 2 minutes and above, hardness reached a constant value of ~180 ±5 Hv. and ΔR calculated from tensile tests increased with increase in annealing time.
Keywords: Lean duplex stainless steel, formability, texture, EBSD, recrystallization.
Audience take away:
- Microstructure evolution and texture development during annealing was linked with mechanical properties.
- Cold rolling resulted in the formation of strain-induced martensite (a’, SIM) from austenite (g) while annealing reversed the effect of cold rolling i.e., reversion of a’ to g.
- The morphology of grains changed from lamellar to near globular with an increase in the annealing time.
- Cold rolled samples showed Brass-type texture for austenite and strong α-fiber (RD//) / γ-fiber (ND//) for ferrite.
- The texture intensity reduced after recrystallization for both austenite and ferrite.