Institute of Quantum Materials Science, IQMS

Interplay magnetic and lattice order of freedom in γ-Fe-C

V. N. Urtsev, Yu. N. Gornostyrev, M. I. Katsnelson, A. V. Shmakov, A. V. Korolev, V. N. Degtyarev, E. D. Mokshin, V. I. Voronin

"Stal", №7 (2010)

The concept of the special structural state with space scale about tens nanometers has been stablish based on assumption on strong spin-lattice coupling in γ-iron. This concept supported y theoretical calculations, microstructure investigations and observed feature of the physical roperties. This structural state is forming before the polymorphic α – γ transformation and his vercooling results in dispersed microstructure formation which distinguish by higher strength nd hardness from bainite and pearlite and have higher plasticity in comparison with martensite.

Equilibrium and metastable states of austenite nearby temperature of α – γ transformation. The appearance of the magnetic short range order results in additional minimum in dependence of the energy ΔE on tetragonal deformation Γt (a); the value Γt >1 in γ-iron (blue curve) and Γt <1 in γ-iron-carbon (red curve). In this system the appearance of the special metastable state take place (b) where fct regions with magnetic short range order are alternated with paramagnetic fcc regions (soliton lattice) and this state stabilize by the inhomogeneities in carbon distribution (c).