Multiaxial isothermal and thermomechanical fatigue behavior of 316LN stainless steel

Effects of multiaxial loading on the isothermal fatigue (IF) and thermomechanical fatigue (TMF) behavior of 316LN stainless steel were comparatively studied. Results showed that the shape of axial stress-strain hysteresis loops was asymmetric in the tensile and compressive half-cycle while the shear hysteresis loops were symmetric. The kernel average misorientation value and low-angle grain boundaries fraction significantly increased, however, the fraction of sigma 3 twin boundaries drastically decreased under multiaxial loading, where the coincidence site lattice value (sigma) represented the reciprocal density of coincident lattice sites between the two adjoining grains. The multiaxial non-proportional loading produced much more damage in comparison to uniaxial loading, consequently a significant reduction in fatigue life, regardless of the IF and TMF loadings. Furthermore, the IF life was the shortest, and the longest life occurred in out-of-phase TMF tests.