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Updated: Mar 6, 2026
08:13
Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area
Published on: February 19, 2018
12.5K
Core-Shell Structure of Intermediate Precipitates in a Nb-Based Z-Phase Strengthened 12% Cr Steel.
Masoud Rashidi1, Hans-Olof Andrén1, Fang Liu1
1Department of Physics,Chalmers University of Technology,SE-412 96 Göteborg,Sweden.
Summary
Z-phase strengthening in 12% Cr steels involves MX to Z-phase transformation. Atom probe tomography revealed Z-phase forms from NbN by chromium diffusion, creating a core-shell structure.
Area of Science:
- Materials Science
- Metallurgy
- Physical Chemistry
Background:
- Creep resistant 12% Cr steels rely on Z-phase precipitates for high-temperature strength.
- The transformation of MX (niobium nitride) to Z-phase (CrMN) is crucial for precipitate distribution and creep strengthening.
Purpose of the Study:
- To investigate the phase transformation mechanism from MX to Z-phase in a niobium-based Z-phase strengthened steel.
- To elucidate the precipitate structure during this transformation using advanced microscopy.
Main Methods:
- Atom probe tomography (APT) was utilized to analyze the nanoscale composition and structure.
- Iso-concentration surfaces and matrix contribution subtraction were employed to visualize transient precipitate structures.
Main Results:
- A core-shell structure of transient precipitates between MX and Z-phase was revealed.
- Z-phase formation was identified as a diffusion-controlled process involving chromium entering niobium nitride (NbN).
- The Z-phase composition was determined to be Cr1+xNb1-xN, with x=0.08.
Conclusions:
- The study clarifies the atomistic mechanism of Z-phase formation in 12% Cr steels.
- Understanding this transformation is key to optimizing precipitate engineering for enhanced creep resistance.
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