Abstract
A 12% Cr model steel was designed with the purpose of studying the nucleation and growth of modified Z-phase, Cr(V,Nb)N. The model alloy develops Z-phase after relatively short ageing times and contains only nitrides of Cr, V and Nb. Interferences from the presence of carbides and the development of Laves phase were avoided by keeping the C, W and Mo contents as low as possible. Transmission electron microscopy and X-ray diffraction analysis of extracted particles were used to follow the evolutions of phase composition, phase morphology and phase fraction, particularly of the precipitation of Z-phase, during ageing at 600, 650 and 700 degrees C for up to 103 h. The development of Z-phase appears to be accomplished by the diffusion of Cr atoms into (V,Nb)N particles and their subsequent conversion into cubic or tetragonal Z-phase. Studies at various temperatures indicate that Z-phase development proceeds fastest at 650 degrees C and that Z-phase forms faster at prior austenite grain boundaries.
Original language | English |
---|---|
Journal | Acta Materialia |
Volume | 58 |
Issue number | 2 |
Pages (from-to) | 669-679 |
ISSN | 1359-6454 |
DOIs | |
Publication status | Published - 2010 |
Keywords
- TEM
- Nitrides
- Heat resistant steels
- Phase transformation kinetics
- XRD