Microstructure and Texture Development during Cold Rolling in UNS S32205 and UNS S32760 Duplex Stainless Steels
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, DARSHAN CHALAPATHI,
In the present study, microstructure and texture evolution during cold rolling in UNS S32205 and UNS S32760 duplex stainless steel was investigated. Both steels were unidirectionally cold rolled up to 80 pct thickness reduction. Scanning electron microscopy and electron backscattered diffraction (EBSD) were used for microstructural characterization, while X-ray diffraction (XRD) was used for the measurement of bulk texture. Strain-induced martensite (SIM) was identified and quantified with the help of magnetic measurements (B–H curve and magnetization saturation). With the increase in plastic strain, the grains became morphologically elongated along the rolling direction with the reduction in average band thickness and band spacing. SIM increased with the increase in deformation and was found to be a function of strain and the SFE of austenite. The increase in SIM was much more pronounced in UNS S32205 steel as compared to UNS S32760 steel. After cold rolling, strong a-fiber (RD//h110i) texture was developed in ferrite, while brass texture was dominant in austenite for both steels. The strength of texture components and fibers was stronger in UNS S32760 steel. Another significant feature was the development of weak c-fiber (ND//h111i) in UNS S32760 steel at intermediate deformation. DOI: 10.1007/s11661-017-4026-9 The Minerals, Metals & Materials Society and ASM International 2017
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INTRODUCTION
DUPLEX stainless steels are well known for their good mechanical strength and corrosion resistance. These are highly alloyed steels consisting of two-phase microstructure (austenite and ferrite in nearly equal proportions) in solution-annealed condition. Duplex stainless steels have better weldability, chloride corrosion resistance, and stress corrosion cracking resistance than most austenitic stainless steels (ASSs).[1] However, austenite in duplex stainless steels is metastable at room temperature, while ferrite is unstable at high temperatures. Further, both these phases are highly supersaturated with alloying elements due to solution annealing treatment and can undergo significant microstructural changes during subsequent thermomechanical treatments. Ferrite can undergo decomposition (diffusional transformation) in the temperature range 573 K to 1273 K (300 C to 1000 C) to form chromium- and
AMIT KUMAR, RAJESH KISNI KHATIRKAR, and DARSHAN CHALAPATHI are with the Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra, India. Contact e-mails: [email protected], [email protected] GULSHAN KUMAR is with the Department of Mechanical Engineering, Thapar University, Patiala 147004, Punjab, India. SATYAM SUWAS is with the Department of Materials Engineering, Indian Institute of Science (IISc), Bengaluru 560012, Karnataka, India. Manuscript submitted May 22, 2016. Article published online March 4, 2017 METALLURGICAL AND MATERIALS TRANSACTIONS A
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