Elucidating microstructural evolution and strengthening mechanisms in nanocrystalline surface induced by surface mechanical attrition treatment of stainless steel

Bahl, Sumit and Suwas, Satyam and Ungar, Tamas and Chatterjee, Kaushik (2017) Elucidating microstructural evolution and strengthening mechanisms in nanocrystalline surface induced by surface mechanical attrition treatment of stainless steel. In: ACTA MATERIALIA, 122 . pp. 138-151.

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Abstract

Surface mechanical attrition treatment (SMAT) is a high strain and strain rate severe plastic deformation (SPD) technique for surface nanocrystallization of metals. The aim of this study was to investigate the mechanism of nanocrystallization and strengthening in a medium stacking fault energy 316 L austenitic stainless steel during SMAT. The paramount role of microband and shear band formation in nano crystallization is outlined, as opposed to deformation twinning previously reported in low SFE austenitic stainless steels. Shear bands undergo dynamic recrystallization and recrystallization twinning to produce ultra-fine grains in contrast to twin-twin intersections in low SFE stainless steel. The ultra-fine grains further sub-divide into smaller cells with initially low misorientation. Nanocrystallization occurs when misorientation between these cells increases with further strain. The additivity of strengthening by dislocation density and grain size is studied. Dislocation density was neglected in previous studies while studying strengthening mechanisms in SMAT processed materials. This study illustrates that dislocation density cannot be ignored as the strengthening mechanism in SMAT process. The grain size and dislocation density both significantly contribute to overall strengthening in SMAT processed microstructure. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Item Type:	Journal Article
Publication:	ACTA MATERIALIA
Additional Information:	Copy right for this article belongs to the PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	07 Jan 2017 10:10
Last Modified:	07 Jan 2017 10:10
URI:	http://eprints.iisc.ac.in/id/eprint/55903

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