The mechanism for the formation of Z-phase was investigated for samples of an 11CrMoVNbN steel aged at 593 °C for up to 50,000 h. X-ray diffraction indicates that Z-phase appears after 5000 h of aging, and its amount gradually increases up to 50,000 h aging at the expense of mainly Cr2N. Transmission electron microscopy shows that Z-phase nucleates in the V-enriched rim region of Cr2N precipitates, which forms due to the diffusion of V into the precipitates from the matrix. Nucleated Z-phase tends to grow relatively rapidly compared with the preexisting precipitates such as Nb(C,N) and M23C6. Z-phase seems to consume Cr2N by the nucleation and growth mechanism rather than the transformation mechanism. The main difference in the aged samples is that the Nb content of Z-phase is lower and that Z-phase does not replace Cr2N completely, compared to the results of the crept samples.
Bibliographical noteFunding Information:
The authors acknowledge the support from the Convergence Agenda Program (CAP) of the National Research Council of Science and Technology (Project No. 2N42980) of Korea and the Technology Innovation Program (Project No. 10063488) funded by the Ministry of Trade, Industry and Energy, Korea.
© 2017 Elsevier Inc.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering