Core-Shell Structure of Intermediate Precipitates in a Nb-Based Z-Phase Strengthened 12% Cr Steel
Journal article, 2017

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+xNb1-xN with x=0.08.

phase transformation

local magnification



9-12% Cr steels

Atom probe tomography


Masoud Rashidi

Chalmers, Physics, Materials Microstructure

Hans-Olof Andrén

Chalmers, Physics, Materials Microstructure

Fang Liu

Chalmers, Physics, Materials Microstructure

Microscopy and Microanalysis

1431-9276 (ISSN) 1435-8115 (eISSN)

Vol. 23 2 360-365

Subject Categories

Materials Engineering

Physical Sciences



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