Recrystallized Grain Structures in Microduplex Iron Nickel Alloys Doped with Niobium or Titanium

Abstract

Microduplex grain structures formed on recrystallization in a two-phase (α+γ) temperature range in cold rolled martensitic Fe-16%Ni alloys have been studied in regard to the influence of the third element, Nb or Ti. The microduplex structures in the binary iron nickel alloy consist of globular γ grains smaller than 2 μm and surrounding α grains having similar sizes and shapes. With the addition of 0.17%Nb microduplex grain sizes are reduced to a quarter of those in the undoped alloy. The grain refinement effect due to Nb or Ti is most striking when the deformed martensite is previously aged at 410°C before recrystallization. It is suggested that the third elements forming intermetallic compounds with Ni play a dominant part in the growth inhibition of the recrystallized grains in the deformed martensite matrix.
Microduplex grains originating from undeformed martensite are acicular and their sizes are almost invariable with the third elements.