Formation of a nanocrystalline structure during direct and reverse martensitic transformations

On the formation of ultra-fine grained Fe-base alloys via phase transformations

“…For example, for fcc austenitic alloys (32Ni, 26Ni-Cr-Ti) with the temperature of the martensitic transformation below room temperature, grain sizes of the order of 10-80 nm have been obtained during forward and reverse martensitic ␥ → ␣ 1 → ␥ transformations [6].…”

Mechanisms of ultrafine-grained austenite formation under different isochronal conditions in a cold-rolled metastable stainless steel

“…8g-h): these images show the formation of defect-free, globular austenite grains of about 200 nm immersed in the martensitic matrix. The globular and defect-free growth of the austenite phase during a reaustenitization process is an indicator of a diffusion-controlled transformation mechanism as previously discussed by other authors [15,18,30,43].…”

“…In the same manner, α-stabilizers (such as Cr) are rejected from the austenite phase. Therefore, Ni-depleted (Cr-rich) regions in direct contact with the austenite phase will exhibit lower A S than martensitic regions further away from the α′/γ interface, which may act as barriers for the grain growth and may inhibit the formation of new austenite at the α′/γ interface [43]. Moreover, it has to be born in mind that the enrichment in Cr around the austenite grains enhances the formation of χ-phase, especially in the range of 600-900°C.…”

Microstructure inhomogeneity of Fe-31%Ni alloy and stabilization of austenite

“…Certain substructure shows up in a volume of grain. After tens of diffusionless α-γ transformations, the fragments of different orientation of reverted austenite reached nanoscale size [4]. % Ni-0.05 wt.% C alloy.…”

“…In particular, in the Fe-Ni alloys, given high temperature and concentration gradients during quenching from melt, the characteristics of martensitic transformations are used to be determined by the cooling speed and the redistribution of nickel on different surfaces of the ribbon and also by the dimension effect of the transformation [1][2][3][4].…”