A. Mateo et al., CHARACTERIZATION OF THE INTERMETALLIC G-PHASE IN AN AISI-329 DUPLEX STAINLESS-STEEL, Journal of Materials Science, 32(17), 1997, pp. 4533-4540
Duplex austenite-ferrite stainless steels are susceptible to a variety
of decomposition processes when aged within the intermediate range of
temperatures (250-500 degrees C). One of these phenomena is the preci
pitation of the intermetallic G-phase. In the present investigation, t
he crystal structure and the chemical composition of the G-phase, prec
ipitated in the ferritic phase of an AlSI329 duplex stainless steel, i
s studied by electron microdiffraction and energy dispersive X-ray spe
ctroscopy. It is determined that the space group of the G-phase is F 4
/m (3) over bar 2/m with a lattice parameter four times that of the fe
rritic matrix. The precipitation mechanism of the G-phase showed a syn
ergetic relation with the ferrite decomposition in Cr-rich and Fe-rich
domains. Based on the obtained results, the structural proximity of f
errite matrix and G-phase has been studied. Further analysis allows to
suggest that the spinodal decomposition leads to an interdomain of a
ferritic structure which is thermodynamically unstable and serves as a
precursory site to the development of the G-phase by atomic position
readjustments inferior to the atomic distances.