Role of Recrystallization and Austenite Formation in Forming (α+γ) Microduplex Structures in Cold Rolled Martensitic Fe-10Ni Alloys

Abstract

For the purpose of finding practical means to obtain ultrafine grain structures, competition between the recrystallization of martensite and the formation of austenite was studied during annealing of cold worked Fe-Ni martensitic alloys in the (α+γ) field.
In an Fe-10%Ni alloy a “microduplex structure” was formed above a critical temperature where the formation of austenite advanced prior to the recrystallization of martensite. Below the temperature the recrystallzation preceded the austenite formation, resulting in a “recrystallized ferrite structure”.
Addition of 0.18%Nb and 0.02%C to the alloy caused marked retardation of recovery and recrystallization of deformed martensite with little effect on the austenite formation. Consequently, an increment of the recrystallized ferrite fraction compared to a given amount of transformed austenite during annealing in the (α+γ) region is reduced to one fifth and the “microduplex structure” can be obtained by annealing at lower temperatures.