EBSD Characterization of Cryogenically Rolled Type 321 Austenitic Stainless Steel
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INTRODUCTION
THE opportunity for substantial enhancement of mechanical properties has given rise to considerable interest in the production of ultrafine-grain microstructures in engineering materials. Typically, this is achieved through the application of severe plastic deformation techniques,[1] but these methods are laborious and difficult to use for the fabrication of commercial-scale quantities. In metastable austenitic stainless steel sheet products, however, substantial grain refinement may be obtained by conventional cold rolling followed by annealing due to the occurrence of a deformation-induced martensitic transformation and the subsequent austenite reversion.[2–17] Among these two processing steps, the deformation
GALIA KORZNIKOVA and AINUR ALETDINOV are with the Institute for Metals Superplasticity Problems, Russian Academy of Science, 39 Khalturin Str., Ufa, Russia, 450001. SERGEY MIRONOV is with the Belgorod National Research University, Pobeda 85, Belgorod, Russia, 308015. Contact e-mail: [email protected] TATYANA KONKOVA is with the Institute for Metals Superplasticity Problems, Russian Academy of Science and also with the University of Strathclyde, 75 Montrose Street, Glasgow, G1 1XJ. RIDA ZARIPOVA is with the Ufa State Aviation Technical University, 12 K. Marx St., Ufa, Russia, 450000. MIKHAIL MYSHLYAEV is with the Baikov Institute of Metallurgy and Material Science, Russian Academy of Science, 49 Lenin-av., Moscow, Russia, 119991 and also with the Institute of Solid State Physics, Russian Academy of Sciences, 2 Academic Osypian Str., Chernogolovka, Moscow Oblast, Russia, 142432. SHELDON SEMIATIN is with the Air Force Research Laboratory, Materials and Manufacturing Directorate, AFRL/RXCM, Wright-Patterson AFB, OH 45433-7817. Manuscript submitted April 13, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
stage appears to be of particular interest because the resulting microstructure essentially determines the final grain refinement effect. Extensive investigation of the phenomenon of the deformation-induced martensitic transformation over ~ 50 years has demonstrated its remarkable complexity.[18] Due to the relatively low stacking fault energy (SFE) of the austenitic steels, plastic straining of such materials is well accepted to be characterized by planar slip, mechanical twinning, and shear banding,[19] features often associated with the dissociation of perfect dislocations into Shockley partials and stacking faults.[20] With increasing dislocation density, the stacking faults may overlap and, depending on the nature of this process, lead to either twinning[21] or the formation of hexagonal-close-packed e-martensite.[22–27] The e-martensite is believed to be a transient phase which eventually transforms into body-centered-tetragonal a¢-martensite.[18,28–33] On the other hand, the direct phase transformation c fi a¢ is also possible.[18,22,28,29,31–37] In this case, the a¢-martensite may nucleate at dislocation pile-ups,[18,22,29,34] mechanical twins,[18,32–37] or deformation bands.[18,28,29,31,32,37]
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