Tensile deformation characteristics of bulk ultrafine-grained austenitic stainless steel produced by thermal cycling

Deformation microstructures of bulk ultrafine-grained austenitic AISI 304L stainless steels were analyzed by electron backscatter diffraction. Samples with grain sizes below 500 nm showed transition from grain-scale deformation to the collective phenomenon of shear banding. This was assisted by strain-induced grain rotation and coalescence. This phenomenon was suppressed in samples with a bimodal grain size distribution (maxima at similar to 650 and similar to 1400 nm) due to deformation-induced martensite formation, yielding high tensile strength and ductility (1348 MPa ultimate tensile strength at 0.36 max. true strain). (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.