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Redistribution of the substitutional elements during σ and χ phase formation in a duplex stainless steel
Author(s) -
Duprez Lode,
De Cooman Bruno C.,
Akdut Nuri
Publication year - 2001
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.200100123
Subject(s) - intermetallic , materials science , austenite , nucleation , metallurgy , grain boundary , ferrite (magnet) , phase (matter) , precipitation , redistribution (election) , atmospheric temperature range , crystallography , analytical chemistry (journal) , thermodynamics , microstructure , chemistry , alloy , composite material , physics , organic chemistry , chromatography , politics , meteorology , political science , law
While the kinetics of intermetallic phase formation in duplex stainless steel have been extensively studied for a wide range of compositions, relatively little research has been done on the mechanisms by which the phases nucleate and grow. In this research the emphasis was on the diffusional growth of the sigma (σ) and chi (χ) phases. Intermetallic phase precipitation in a standard DSS type EN 1.4462 was studied in detail at two temperatures: at 850 °C where large amounts of σ phase are formed, and at 650 °C where χ is the main intermetallic phase. The redistribution of the substitutional alloying elements Cr, Mo, Ni, Mn and Si between the ferrite, the austenite and the intermetallic phases was followed by means of scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX). Mn and Si showed no distinct partitioning between the several phases. The diffusion paths of the other elements were found to be determined by two phenomena. On the one hand, the ferrite to austenite transformation causes Mo and Cr to enrich in the ferritic phase and Ni to enrich in the austenite. On the other hand, Mo (σ, χ) and Cr (σ) are removed from the ferrite by intermetallic phase precipitation. At 650 °C, strong Mo enrichments appear at the α‐γ phase boundaries indicating that grain boundary diffusion could be an important mechanism for Mo to diffuse to the growing χ phase.