Role of magnetic degrees of freedom in a scenario of phase transformations in steel
Abstract
The diversity of mesostructures formed in steel at cooling from a hightemperature austenite (γ) phase is determined by the interplay of shear reconstructions of crystal lattice and diffusion of carbon. Combining firstprinciples calculations with largescale phasefield simulations we demonstrate a decisive role of magnetic degrees of freedom in the formation of energy relief along the Bain path of γα transformation and, thus, in this interplay. We show that there is the main factor, namely, the magnetic state of iron and its evolution with temperature which controls the change in character of the transformation. Based on the computational results we propose a simple model which reproduces, in good agreement with experiment, the most important curves of the phase transformation in FeC, namely, the lines relevant to a start of ferrite, bainite, and martensite transformations. Phasefield simulations within the model describe qualitatively typical patterns at these transformations.
 Publication:

Physical Review B
 Pub Date:
 September 2014
 DOI:
 10.1103/PhysRevB.90.094101
 arXiv:
 arXiv:1408.3275
 Bibcode:
 2014PhRvB..90i4101R
 Keywords:

 63.70.+h;
 64.60.qe;
 71.15.Nc;
 75.50.Bb;
 Statistical mechanics of lattice vibrations and displacive phase transitions;
 General theory and computer simulations of nucleation;
 Total energy and cohesive energy calculations;
 Fe and its alloys;
 Condensed Matter  Materials Science
 EPrint:
 Phys. Rev. B 90, 094101 (2014)