Cyclic deformation behaviour and stability of grain-refined 301LN austenitic stainless structure

Abstract

Low cycle fatigue (LCF) behaviour of metastable austenitic 301LN stainless steel with different grain sizes – coarse-grained (13 μm), fine-grained (1.4 μm) and ultrafine-grained (0.6 μm) – produced by reversion annealing after prior cold rolling was investigated. Fully symmetrical LCF tests with constant total strain amplitudes of 0.5% and 0.6% were performed at room temperature with a low constant strain rate of 2×10-3 s-1. Microstructural changes in different positions within the gauge part of the specimens were examined by optical microscopy (polarized light) and electron backscatter diffraction (EBSD) technique; for quantitative assessment of the volume fraction of deformation induced martensite (DIM) a Feritscope FMP 30 was adopted. The cyclic stress-strain response and specific changes of hysteresis loop shapes in the very early stage of cycling are confronted with the character of DIM formation and its distribution in the whole volume of the material. A possible effect of strain rate (frequency of cycling) on the destabilization of austenitic structure during cyclic straining of materials with different grain sizes is highlighted.

Processing and Properties of Reversion-Treated Austenitic Stainless Steels

“…The effect of the GS refinement on fatigue strength has been studied extensively in nano-structured materials and also in metastable ASSs [43,60,64,74,87,[180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195][196]. GS can be refined by various means in addition to the reversion, too.…”

The role of grain size in static and cyclic deformation behaviour of a laser reversion annealed metastable austenitic steel

“…Moreover, in some works, the range of applied strain amplitudes is limited to relatively high values of Δε t /2 ≥ 0.6% 22 or only two different strain amplitudes have been applied at all. 24,25 Therefore, the present work aims to follow up on this research by investigating a broader range of total strain amplitudes and average grain sizes.…”

“…Furthermore, several works on the grain‐size dependence of the fatigue behaviour of austenitic steels have been published, so far. Some of them were based on stress‐controlled tests, 15,17–20 others based on strain‐controlled tests 21–25 . In materials exhibiting pronounced cyclic hardening, the control mode is an essential factor regarding the fatigue behaviour and, in particular, the fatigue life.…”

“…The work of Droste et al 21 investigated the influence of an average grain size below 1 μm, whereas the study of Chlupova et al 23 suffers upon a lack of data points for a persuasive lifetime estimation inhibiting a comparison between the material states. Moreover, in some works, the range of applied strain amplitudes is limited to relatively high values of Δε t /2 ≥ 0.6% 22 or only two different strain amplitudes have been applied at all 24,25 . Therefore, the present work aims to follow up on this research by investigating a broader range of total strain amplitudes and average grain sizes.…”

“…Some of them were based on stress-controlled tests, 15,[17][18][19][20] others based on straincontrolled tests. [21][22][23][24][25] In materials exhibiting pronounced cyclic hardening, the control mode is an essential factor regarding the fatigue behaviour and, in particular, the fatigue life. Nevertheless, only few of the works based on strain-controlled tests 21,23 include considerations on fatigue life.…”