Structural mechanism of reverse α→ γ transformation and new functional properties of Fe-Ni austenitic alloys

摘要

The structure of the metastable austenite Fe-32%Ni alloy quenched for martensite and subjected to the α→ γ transformation at slow heating (to 593-773 K) with the formation of a nanocrystalline austenite of different orientation was investigated. Electron diffraction analysis has revealed that a nickel-enriched nanocrystalline y-phase acquires ordered L1_0 superstructure. Together with the y-phase, there was detected the disperse E-martensite with a hexagonal close-packed (hcp) lattice. Along with the realization of ordinary orientation relationships (ORs) of Kurdjumov-Sachs, between a matrix α-phase and an ordered y-phase in the sample of Fe-32%Ni alloy after slow heating to 773 K there have been established Headley-Brooks ORs. Cyclic transformation promotes the improvement of many functional properties of steels (strength, coercive force, controlled thermal expansion coefficient, and others).