Papers by Author: V.V. Sagaradze

Abstract: It has been shown that the conversion of austenitic manganese steels – via their purposeful alloying – into the class of precipitation-hardening materials (when aging leads to the formation of VC carbides) provides for high values (2.5-2.7 %) of the shape memory effect (SME) and considerable improvement in strength characteristics of the steels after aging and implementation of γ→ε→γ transformations. Strength characteristics and SME can be governed in wide limits by means of controlled changing of the amount, dispersity, and distribution of VC carbides during aging. The shape memory effect with a reversible deformation of 1.6—1.7% in the metastable steels such as 0.20C-20Mn-2Si-1V with an ε–martensite initial structure is obtained as a result of the retwinning of ε martensite during cold deformation and the subsequent ε→γ transformation during heating.

Abstract: 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 nickel-enriched nanocrystalline γ-phase obtain ordered L10 superstructure. Together with the γ-phase, there was detected the disperse ε-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 γ-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, controlling of the thermal expansion coefficient and others).