arXiv subjects

M. V. Petrik

Publications and source records attributed to M. V. Petrik.

2 recordsLinked to original sources

arXiv2017

Ab initio based analysis of grain boundary segregation in Al-Mg and Al-Zn binary alloys

Based on ab-initio simulations, we report on the nature of principally different mechanisms for interaction of Mg and Zn atoms with grain boundaries in Al alloys leading to different morphology of segregation. The Mg atoms segregate in relatively wide GB region with heterogeneous agglomerations due to the deformation mechanism of solute-GB interaction. In contrast, in the case of Zn atoms an electronic mechanism associated with the formation of directional bonding is dominating in the solute-GB interaction. As a result, for Zn atoms it is energetically beneficial to occupy interstitial positions at the very GB and to be arranged into thin layers along the GBs. The results obtained show the essential role of elements chemistry in segregation formation and explain the qualitative features in morphology of GB segregation observed in Al-Mg and Al-Zn alloys with ultrafine grains.

cond-mat.mtrl-sci↗

arXiv2014

Role of magnetic degrees of freedom in a scenario of phase transformations in steel

The diversity of mesostructures formed in steel at cooling from a high-temperature austenite ("gamma") phase is determined by the interplay of shear reconstructions of crystal lattice and diffusion of carbon. Combining first-principles calculations with large-scale phase-field simulations we demonstrate a decisive role of magnetic degrees of freedom in the formation of energy relief along the Bain path of "gamma"-"alpha" 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 Fe-C, namely, the lines relevant to a start of ferrite, bainite, and martensite transformations. Phase-field simulations within the model describe qualitatively typical patterns at these transformations.

cond-mat.mtrl-sci↗