Synergistic effect of Cu and Ni on the formation of reversed austenite in super martensitic stainless steel

Abstract

The interplay of Cu and Ni on the formation of reversed austenite in super martensitic stainless steel (SMSS) was discussed in this study. Ni concentration in reversed austenite increases from 9.93 to 11.96 wt-% as Cu content increases from 1.5 to 3 wt-%, while Cu concentration increases from 1.43 to 1.89 wt-% as Ni increases from 5 to 6.5 wt-%. The enrichment of Ni and Cu in reversed austenite is much higher than that in martensite matrix. Reversed austenite formed in the dispersion area of ε-Cu inherits the twinning structure of ε-Cu and the crystal orientation relationship with the matrix during tempering. So Cu helps increase the enrichment of Ni, which in turn promotes Cu enrichment and induces the precipitation of ε-Cu due to the reduction of interfacial energy for reversed austenite formation. Our work reveals the synergism of Cu and Ni on the formation of reversed austenite.