Please use this identifier to cite or link to this item:
Title: Identification of sigma and chi phases in duplex stainless steels
Author: Llorca i Isern, Núria
López-Luque, Héctor
Lopez-Jimenez, Isabel
Biezma, María Victoria
Keywords: Acer inoxidable
Transformacions de fase (Física estadística)
Stainless steel
Phase transformations (Statistical physics)
Issue Date: 8-Dec-2015
Publisher: Elsevier B.V.
Abstract: The aim of this work is to find out the most suitable method for detecting and analyzing accurately the formation conditions of secondary phases, particularly Sigma-phase (σ-phase) and Chi-phase (χ-phase) in duplex stainless steels (UNS S32205 and UNS S32750). The microstructure was characterized after a solution annealing at 1080 °C followed by an isothermal heating at 830 °C for different time ranges, ranging from 1 min to 9 h, in order to enlighten the controversial point concerning the mechanism of χ-phase nucleation in relation with the σ-phase. Etched samples were observed using optical microscopy (MO), and scanning electron microscopy (FESEM) with a backscattered electron detector (BSE) was used on unetched samples. Compositional microanalysis (EDS) was carried out for identifying the different phases present in the steels. Sigma phase was easily observed using different etching procedures, whereas χ-phase was only clearly detected with FESEM BSE on unetched samples. The compositional analyses showed that the molybdenum content in χ-phase almost doubles the content of this element in σ-phase, and as a result the kinetics of nucleation and growth were also found to be remarkably faster when the alloy content in the steel is higher. In addition, chromium nitrides and carbides were also observed to precipitate as a result of the heat treatments and, in the case of the chromium nitrides, they act as a favorable site for the nucleation of σ-phase and χ-phase.
Note: Versió postprint del document publicat a:
It is part of: Materials Characterization, 2015, vol. 112, p. 20-29
Related resource:
ISSN: 1044-5803
Appears in Collections:Articles publicats en revistes (Ciència dels Materials i Química Física)

Files in This Item:
File Description SizeFormat 
657557.pdf3.44 MBAdobe PDFView/Open

This item is licensed under a Creative Commons License Creative Commons