DISLOCATION-STRUCTURES IN THE BANDS OF LOCALIZED CYCLIC PLASTIC STRAIN IN AUSTENITIC 316L AND AUSTENITIC-FERRITIC DUPLEX STAINLESS-STEELS

Dislocation structures in bands corresponding to cyclic strain localis ation have been studied in two types of stainless steels, single phase austenitic 316L steel and two-phase austenitic-ferritic duplex steel Dislocation structures are documented in thin foils oriented approxima tely perpendicular to the active slip plane of individual grains and p arallel to the primary Burgers vector. Persistent slip bands, with the structure more or less reminiscent of the well-known ladder structure , were found in austenitic grains of both steels. These bands can be c orrelated with the distinct surface relief consisting of extrusions, i ntrusions and shallow surface cracks in austenitic phase. No clear fea tures which can prove the existence of the persistent Luders bands in austenitic grains were found. The distribution of the wall and labyrin th structure embedded in the matrix structure in ferritic grains, whic h was proposed to be responsible for the localisation of the cyclic st rain, however, does not correspond to the distribution of the distinct surface slip lines on the surface. (C) 1997 Acta Metallurgica Inc.