Core-Shell Structure of Intermediate Precipitates in a Nb-Based Z-Phase Strengthened 12% Cr Steel. (20th March 2017)

• Record Type: Journal Article
• Authors: Rashidi, Masoud; Andrén, Hans-Olof; Liu, Fang
• Editors: Thuvander, Mattias; Cairney, Julie; Gerstl, Stephan
• Is Part Of: Microscopy and microanalysis. Volume 23:Number 2(2017)
• Page Start: 360
• Page End: 365
• Publication Date: 2017-03-20
• Subjects: Atom probe tomography, -- phase transformation, -- 9–12% Cr steels, -- Z-phase, -- local magnification, -- precipitates; Microscopy -- Periodicals; Microchemistry -- Periodicals; 502.82
• DOI: 10.1017/S1431927617000174
• Languages: English
• ISSNs: 1431-9276

Abstract

Abstract: In creep resistant Z-phase strengthened 12% Cr steels, MX (M=Nb, Ta, or V, and X=C and/or N) to Z-phase (CrMN, M=Ta, Nb, or V) transformation plays an important role in achieving a fine distribution of Z-phase precipitates for creep strengthening. Atom probe tomography was employed to investigate the phase transformation in a Nb-based Z-phase strengthened trial steel. Using iso-concentration surfaces with different concentration values, and subtracting the matrix contribution enabled us to reveal the core-shell structure of the transient precipitates between MX and Z-phase. It was shown that Z-phase forms by diffusion of Cr into NbN upon ageing, and Z-phase has a composition corresponding to Cr1+ x Nb1− x N with x =0.08.