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Microsc Microanal. 2017 Apr;23(2):385-395. doi: 10.1017/S1431927617000150. Epub 2017 Mar 21.

Interface Segregation and Nitrogen Measurement in Fe-Mn-N Steel by Atom Probe Tomography.

Author information

1
1Department of Materials Science and Engineering,McMaster University,1280 Main St. W.,Hamilton,ON,Canada.
2
2SIMaP,UMR 5622,Grenoble INP - CNRS - UGA,1130 rue de la piscine,BP75,F-38420 St Martin d'Hères,France.

Abstract

Improved understanding of the interactions between solutes and the austenite/ferrite interface can benefit modeling of ferrite growth during austenite decomposition, as the transformation kinetic is significantly affected by solutes that influence interface mobility. Solute-interface interactions dominate solute segregation at the interface in binary systems, but in multi-component alloys, solute-solute interactions may also affect segregation. In this study, interface segregation in Fe-Mn-N is examined and compared with Fe-Mn-C, to reveal the extent to which C affects the segregation of Mn. Atom probe tomography (APT) is well-suited to analyze solute concentrations across the interface, as this technique combines high spatial resolution and compositional sensitivity. Measurements of Mn show that segregation is only observed for Fe-Mn-C. This demonstrates that Mn segregation is primarily driven by an affinity for C, which also segregates to the interface. However, the measurement of N in steels by APT may be affected by a variety of experimental factors. Therefore, in verifying the Fe-Mn-N result, systematic examination is conducted on the influence of pulsing method (voltage versus laser), sample preparation (ion milling versus electropolishing), and vacuum storage on the measured N concentration. Both laser pulsing and focused ion beam sample preparation are observed to decrease the apparent N concentration.

KEYWORDS:

atom probe tomography; interface segregation; martensite; nitrogen quantification; steel

PMID:
28322178
DOI:
10.1017/S1431927617000150

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