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

Dislocation structures in two heats of 316L austenitic stainless steel s, cyclically strained at room temperature with constant plastic strai n amplitude over a wide interval, were studied. The spatial arrangemen t of dislocations in the grains was determined using the technique of oriented foils. The main types of dislocation structures, characterist ic of amplitudes corresponding to three regimes of cyclic stress-strai n curves, and their proportions as a function of the plastic strain am plitude and the number of cycles, were evaluated. In each regime of cy clic stress-strain curve a dominant dislocation structure was found: p lanar dislocation arrays arranged in sheets in regime I(epsilon(ap) < 1 x 10(-4)), imperfect vein structure with persistent slip bands in th e 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).