The effects of the strain amplitude and the strain ratio, in low-cycle fatigue at 0.25Hz, upon the final stable dislocation structure of a failed specimen were investigated in a duplex stainless steel. The morphology of the fatigued dislocation microstructure in the α phase consisted of dislocation-cell structures and of persistent slip bands. No dislocation loop patches or labyrinths were observed in the α grains. Instead, persistent slip bands and worm-like persistent slip band loops embedded in a highly dense dislocation matrix were found, and the dislocation density increased with increases in the strain amplitude and the tensile mean strain; which changed the strain ratio. The morphology of the fatigued dislocation structure in the γ-phase was characterized by the presence of strain-induced martensite.

The Effect of Strain Ratio on Morphology of Dislocation in Low Cycle Fatigued SAF 2205 DSS. P.K.Chiu, S.H.Wang, J.R.Yang, K.L.Weng, J.Fang: Materials Chemistry and Physics, 2006, 98[1], 103-10