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AFM study of slip localization and surface relief evolution in fatigued ferritic XlOCrA124 stainless steel

J. an" J . ~ o l g k ' , M. v%ar2, K. Obrtlikl, J. ~ a t ~ j k o v h ~ & A. ~ e k ' I Institute of Physics of Materials, Brno, Czech Republic 2 Czech Metrology Institute, Brno, Czech Republic 3~nstitute of Scientific Instruments, Brno, Czech Republic

Abstract

Atomic force microscopy (AFM) was applied to study the surface relief evolution at the emerging persistent slip bands (PSBs) in individual grains of polycrystalline ferritic stainless steel cycled with constant plastic strain amplitude. The surface relief starts to develop early in the fatigue life (at 0.2- 0.5% Nf) due to the localization of the cyclic plastic strain into PSBs. The appearance of the first persistent slip markings (PSMs) correlates with the cyclic hardening/softening curve and with the characteristic variations in the loop shape parameter VH. Surface relief of the well-developed individual PSMs consists of extrusions with fine irregular structure, but also of intrusions laying both parallel to the extrusions and within the PSMs. The extrusion height can be assessed by a direct observation of the metal surface and the intrusion depth using the plastic replica technique. PSBs can be active during the whole fatigue life. The high initial extrusion growth rate of (3.4-6.2)~10-" mkycle decreases during the fatigue life without, however, ceasing completely. During most of the fatigue life the growth rates of extrusions were in the interval (0.6-1.2)~10-" mlcycle. The experimental results are discussed in terms of vacancy models of surface relief evolution.

Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

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Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533

Transactions on Engineering Sciences vol 40, © 2003 WIT Press, www.witpress.com, ISSN 1743-3533