Microstructure evolution of a Z-phase strengthened 9-12% Cr steel
Paper in proceedings, 2011
A new alloy design concept for martensitic / ferritic steels aiming for 650°C – the Zphase
strengthened steels – has been developed in Europe. These new steels are
expected to have good corrosion and creep resistance, which is attributed to a high Cr
content (up to 12 %) and a dense distribution of stable Z-phase precipitates.
This paper reports a study of the microstructure evolution of a trial Ta-containing Zphase
strengthened steel. Samples with different aging times, from 24 hours to 10,000
hours, were investigated by using scanning electron microscopy and transmission
electron microscopy. Mainly two types of precipitates, Z-phase and Laves phase, were
found. The size distribution of the precipitates was analysed. It was found that Zphase
precipitates, with very small initial size, have a very low coarsening rate.