Texture Development in High-Silicon Iron Sheet Produced by Simple Shear Deformation
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UCTION
PROCESSING of metal ingot and billet into sheet and foil is usually done by rolling, combining multiple hot- and cold-rolling steps involving incremental reductions.[1] Intermediate annealing treatments also may be required between cold-rolling steps to maintain sufficient workability in the material. While using rolling as an approach to sheet production has important advantages in terms of scalability and production, there are also some major disadvantages. These include low energy efficiency associated with the multiple reduction and annealing steps, inhomogeneous deformation in the early reduction stages, limited control of texture for influencing material properties, and difficulty in processing alloys of poor workability. Workability, in the current context, broadly refers to the ability of the material to sustain moderate-to-large deformations in sheet processing without problems such as flow localization, segmentation, and cracking.
ANDREW B. KUSTAS, Ph.D. Candidate, and KEVIN P. TRUMBLE, Professor, are with the School of Materials Engineering, Center for Materials Processing and Tribology, Purdue University, 701 West Stadium Avenue, West Lafayette, IN 47907. Contact e-mail: [email protected] DINAKAR SAGAPURAM, formerly Postdoctoral Research Fellow with the School of Industrial Engineering, Center for Materials Processing and Tribology, Purdue University, is now Assistant Professor with Texas A&M, College Station. SRINIVASAN CHANDRASEKAR, Professor, is with the School of Industrial Engineering, Center for Materials Processing and Tribology, Purdue University. Manuscript submitted September 24, 2015. Article published online March 22, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
In recent studies,[2,3] Mg alloys of poor workability could be processed into sheet form in a single step of simple shear deformation by constrained cutting-extrusion. This deformation process—large-strain extrusion machining (LSEM)—could create a range of shear textures in the sheet, with conditions of near-adiabatic heating and large hydrostatic pressure prevailing in the deformation zone. Flow localization was avoided though constrained deformation that suppresses geometric softening. While the poor workability of HCP metals is due largely to flow localization in large-strain deformation and/or insufficient slip systems to accommodate the deformation, workability issues in many BCC and FCC systems are often a consequence of alloying addition. The current study explores the use of simple shear to process BCC alloys of poor workability into sheet form, with shear textures and uniform fine-grained microstructure, in a single deformation step. The model system chosen is Fe alloys of high Si content (‡ 4 wt pct Si), since this system is well known to have limited workability.[4] Furthermore, the system is the basis for electrical steels widely used in transformers and motors.
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BACKGROUND
A. Electrical Steel Sheet Electrical steel or iron silicon (Fe-Si) alloys in sheet/foil forms have long been utilized for their magnetic and ele
