Nanocrystalline structure in Fe—Ni solid alloys prepared via thermal cycling

Abstract

The effect of the number of polymorphic α → γ → α transformation cycles on the structural features of the a phase is studied on Fe—Ni alloys with Ni content of 5 to 24 at %. It is established that the typical structural parameter—the lath width of the packet martensite—is abruptly decreased at the first transformation cycle and slightly reduced with a further increase in the number of transformation cycles conducted in the same mode. The increased nickel content leads to the decrease in the temperatures of the forward and reverse transformations, reduction of the temperature range of transformation, and increase in the amount of the nontransformed γ phase (residual austenite). The martensite lath width is therewith reduced and attains 0.1–0.2 µm in the alloy with 24 at % Ni after five transformation cycles.