Effect of Bolide Former Elements on Recovery and Recrystallization of Reverse-transformed Austenite in Fe-19%Ni Alloy

Abstract

Effect of various bolide former elements on recovery and recrystallization of reverse-transformed austenite was examined in carbon-free Fe-19mass%Ni alloys. The combined addition of Nb and B was found to be most effective in suppressing them, because the recrystallization of reverse-transformed austenite rose up to 1200K, which was 100K higher than that of nothingadded alloy. TEM observation of extraction replicas indicated that their retardation was due to very fine precipitates of Nb-bolide. It was evident from the theoretically obtained solubiliy products of several MB₂-type bolides (M:Cr, Mn, Nb, Ti, Mo) that NbB₂ was more stable than the other bolides up to high temperature. This may be the reason why recovery and recrystallization are suppressed up to the highest temperature by the combined addition of Nb and B.