DISLOCATION-STRUCTURES IN 316L STAINLESS-STEEL CYCLED WITH PLASTIC STRAIN AMPLITUDES OVER A WIDE INTERVAL

Dislocation structures in two heats of 316L austenitic stainless steels, cyclically strained at room temperature with constant plastic strain amplitude over a wide interval, were studied. The spatial arrangement of dislocations in the grains was determined using the technique of oriented foils. The main types of dislocation structures, characteristic of amplitudes corresponding to three regimes of cyclic stress-strain curves, and their proportions as a function of the plastic strain amplitude and the number of cycles, were evaluated. In each regime of cyclic stress-strain curve a dominant dislocation structure was found: planar dislocation arrays arranged in sheets in regime I(epsilon(ap) < 1 x 10(-4)), imperfect vein structure with persistent slip bands in the plateau regime II (1 x 10(-4) < epsilon(ap) < 1 x 10(-3), and cells and wall structures in regime III (epsilon(ap) > 1 x 10(-3).