Effect of Interlamellar Spacing on the Low Cycle Fatigue Behavior of a Fully Pearlitic Steel

Abstract : The present study aims at investigating the low cycle fatigue behavior of two fully AISI 1080 pearlitic steels which differed in their interlamellar spacing (72 ± 15 and 143 ± 32 nm). Low cycle fatigue tests were performed under positive strain control at different total strain variations (0.6% ≤ Δεt ≤ 1.6%). It is shown that both alloys presented an asymmetric stress response and a cyclic softening during the first fatigue life fractions. The tension stress peaks were higher for the fine pearlitic steel than for the coarse one but the compression stress peaks were less different. The extrusion–intrusion pairs formed at the external surface were more developed for the coarse pearlitic steel. The results suggest that the critical short crack size to propagate in the bulk is much smaller in the fine pearlitic steel which explains the shorter fatigue lives. For both steels, the entire fracture surface comprised a fatigue propagation zone, a final fully brittle zone separated by a narrow ductile transition zone.