Torsional thermomechanical fatigue behavior of 316LN stainless steel

Torsional thermomechanical fatigue behaviors of 316LN stainless steel at various equivalent shear strain amplitudes (0.6%, 0.8%, 1.0%, 1.2%) were investigated. A prolonged secondary hardening occurring exclusively at the strain amplitude of 0.6% was ascribed to the dominance of a planar slip mode in plastic deformation. As a strengthening mechanism, the occurrence of dynamic strain aging at the strain amplitude of 1.0% offset the magnitude of cyclic softening partially. The fatigue-dominated failure behavior with the formation of representative shear-type cracks was assisted by oxidation damage. The preferential oxidation along surface dense slip bands accelerated the micmcrack nucleation and crack growth, leading to a bilinearity decrease in fatigue life with increasing strain amplitudes.