On the Precipitation of Sigma and Chi Phases in a Cast Super Duplex Stainless Steel

• Type: Article in International Scientific Journal
• Date: 2019-08-19

Authors

Ricardo O. Sousa (Author) FEUP; Laura Ribeiro (Author) FEUP; P. J. Ferreira (Author) Other; P. Lacerda (Author) Other

Journal

Title: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Vol. 50A No. 10

Pages: 4758-4778

ISSN: 1073-5623

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 0 Citations

Scopus - 6 Citations

Other information

Authenticus ID: P-00Q-Z3Y

DOI: 10.1007/s11661-019-05396-6

Abstract (EN): Super duplex stainless steels are prone to the formation of undesirable secondary phases, particularly when exposed to slow cooling rates. In the current study, the mechanisms of formation of secondary phases have been characterized using a combination of optical microscopy, scanning electron microscopy, and transmission electron microscopy, on samples aged at temperatures ranging between 700 degrees C and 1000 degrees C. Among the possible secondary phases, chi-phase and sigma-phase were detected and identified as the main phases responsible for the destabilization of the duplex microstructure. The kinetics of both phases were assessed. In particular, the chi-phase forms prior to sigma-phase, until it starts to convert into sigma-phase. Finally, the TTT curves for the stable sigma-phase were calculated. We found that the precipitation of the sigma-phase starts as early as 30 seconds at 950 degrees C.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 21