Characterization of Dislocation Structure in a Nb-bearing Austenitic Stainless Steel After Low Cycle Fatigue via TEM and EBSD

Abstract

In this paper, the relationship between Kernel average misorientation (KAM), geometrically necessary dislocation (GND) density and dislocation structures of Nb-bearing austenitic stainless steel under low cycle fatigue (LCF) was studied at 600°C at the total strain amplitude ranged from 0.3% to 1.0%. The results based on EBSD analysis show that the GND density in fatigue specimens gradually increases with the increase of strain amplitude. Under LCF loading, the dislocation structures are mainly planar slip bands (PSBs) and the cell structures. With the increase of strain amplitude, the number of PSBs increases with decrease in width, and the average diameter of cells also decreases. The PSBs originate due to the dynamic strain aging (DSA) effect, and DSA is more significant under high strain amplitude. The average diameter of cell structures has a specific relationship with GND density.

Effect of Aging Temperature on Plastic Flow Behaviour and Toughness of Nickel Free High Nitrogen Austenitic Stainless Steels

“…n are constants 10 . It has been reported [8][9][10][11][12][13][14][15] that the composition and the temperature of deformation of austenitic stainless steels influenced strain hardening behaviour and its relation to dislocations arrangement. Schröder et al 16 reported that Mn increase the ultimate tensile strength of metastable austenitic stainless steels.…”

“…Presence of larger precipitates facilitated easy pull out from GB than smaller precipitates at low temperatures. This reduction in cohesive strength leads to reduction of bond strength 15 . Cracks may initiate due to pull out of precipitates from GBs 3,15 and propagate along GBs.…”

A comprehensive review and analysis of Masing/non‐Masing behavior of materials under fatigue

“…The main disadvantages are as follows: (1) the nonconservative estimation of CPSED and consequently fatigue life, 25,94 (2) the necessity of master curve formation, 140 and (3) it can be used for estimation only, not for prediction of CPSED 6 . Despite these limitations, this equation has extensively been used to estimate engineering materials' CPSED and fatigue life 25,141–143 . In order to avoid the necessity of master curve formation and be able to predict the CPSED and fatigue life, Yadav et al 12 have proposed a new method.…”

“…6 Despite these limitations, this equation has extensively been used to estimate engineering materials' CPSED and fatigue life. 25,[141][142][143] In order to avoid the necessity of master curve formation and be able to predict the CPSED and fatigue life, Yadav et al 12 have proposed a new method. The method is originally proposed for materials with non-Masing behavior of Type-II, that is, when the master curve cannot be constructed.…”