Cyclic deformation behavior of 316LN under non-proportional loading based on the analysis on the hysteresis loop and microstructure

The evolution of the effective and internal stresses of 316LN under total strain controlled non-proportional loadings is presented by partitioning the hysteresis loop, and the microstructure evolution was studied by transmission electron microscopy observation on specimens loaded with different cycles. Particular attention was paid to the two different contributions of the internal stress, intergranular and intragranular components, which were studied by taking into account quantitatively the heterogeneous dislocation structures. As compared with uniaxial loadings, the dislocation structures were observed with higher heterogeneity and density under non-proportional loadings, especially at the beginning of cycling. The dislocation rearrangement from planar structure to heterogeneous distribution occurred during the initial hardening stage led to not only an increase in the intragranular component which dominates the initial cyclic hardening, but also a decrease in the intergranular one which induces the following cyclic softening. Moreover, the hardening with the loading non-proportionality was also determined mostly by the intragranular component.