Atomic force microscopy of surface relief in individual grains of fatigued 316L austenitic stainless steel

Surface relief adjacent to the persistent slip bands (PSBs) in polycrystalline 316L stainless steel cycled with constant plastic strain amplitude up to 60% of fatigue life was studied using atomic force microscopy with respect to the crystallographic orientation (determined by electron backscattering diffraction-EBSD) and the size of individual grains. Surface relief is formed mostly by ribbon-like extrusions whose height in a grain was found to be proportional to the thickness of the corresponding PSB. The extrusions grow predominantly in the direction of the active Burgers vector. The height of an extrusion in the direction of the active Burgers vector is proportional to the grain size. No systematic dependence of the extrusion height in the active slip direction on the grain orientation was observed. The experimental results are discussed in terms of the recent vacancy models of surface relief evolution. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.