Experimental and theoretical investigation of precipitate coarsening rate in Z-phase strengthened steels
Journal article, 2018

Two Z-phase strengthened 12% Cr steels were investigated: they are similar in composition, however one steel contains Nb and the other contains Ta. Z-phase precipitates (CrMN, M = Nb or Ta) provide precipitation hardening for creep resistance at 650 °C in these steels. Experimental data based on the transmission electron microscopy investigation of the size evolution of Z-phase precipitates during isothermal ageing at 650 °C show that the Ta-based Z-phase benefits from a five times smaller coarsening constant compared to the Nb-based Z-phase. Theoretical calculations show that this is attributed to the smaller diffusivity of Ta compared to Nb in the steel matrix. Besides, comparing the size of the Ta-based Z-phase precipitates in the gauge and head portion of a crept specimen, it is shown that Z-phase coarsens faster under stress.


Masoud Rashidi

Chalmers, Industrial and Materials Science, Materials and manufacture

Joakim Odqvist

Royal Institute of Technology (KTH)

Lennart Johansson


John Hald

Technical University of Denmark (DTU)

Hans-Olof Andrén

Chalmers, Physics, Materials Microstructure

Fang Liu

Chalmers, Industrial and Materials Science, Materials and manufacture


2589-1529 (ISSN)

Vol. 4 247-254

Subject Categories

Physical Chemistry

Metallurgy and Metallic Materials



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