Comparison of the rate of decomposition in Fe45%Cr, Fe45%Cr5%Ni and duplex stainless steels

A comparison has been made of the rate of decomposition of the ferrite in an Fe45%Cr, an Fe45%Cr5%Ni and the ferrite phase of two CF 3 duplex stainless steels during long term ageing at 400°C. In all these systems, the ferrite phase decomposes upon ageing to form an ultrafine-scale interconnected network structure of an iron-rich α phase and a chromium-enriched α′ phase. The addition of nickel to the binary Fe45%Cr alloy significantly increases the hardness of the alloy and also accelerates the kinetics of decomposition. Although the hardness data from the ternary alloys are similar to those of the ferrite phase in the duplex stainless steels, significant differences were also observed in the scale and composition amplitudes of the α and α′ phases.