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Figure 2 | Nanoscale Research Letters

Figure 2

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

Figure 2

Martensitic volume part vs the number of γ- α- γ cycles. Change of the martensitic volume part vs the number of γ-α-γ cycles for the contact (1), free (2) surfaces of a spinning ribbon, and bulk (3) Fe-30.6 wt.% Ni-0.05 wt.% C alloy. Reduction of the size of austenitic grain in melt-spun ribbons results in more considerable stabilization of reverted austenite as compared to the bulk alloy of the same chemical composition. It was found that after 30 γ-α-γ cycles of reverse diffussionless transformations in the ribbon, the amount of martensite on a free side dropped by 61%, on a contact side by 43%, while in a bulk alloy, only by 8%. Investigations indicated that the size effect of martensitic transformation yielded a higher degree of stabilization of reverted austenite on a free side of the ribbon as compared to a contact side. Quenching in liquid nitrogen caused essential difference of grain structure on both the sides of the ribbon as well as the gradient distribution of the amount of martensitic phase inside it. Austenitic grains on a contact surface was smaller than on a free surface. As a result of the size effect of the transformation, amounts of martensitic phase on a contact and free surfaces were different - 59% and 82%, respectively.

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