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arXiv · 1510.04358

Titanium $α- ω$ phase transformation pathway and a predicted metastable structure

N. A. Zarkevich·D. D. Johnson
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Abstract

As titanium is a highly utilized metal for structural light-weighting, its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Impurities, pressure, and temperature control the phase stability and transition barriers in most industrial and geophysical materials - in Ti, interstitial O, N, or C retard while substitutional Al and V suppress the $ω$ phase. Using a proper solid-state nudged elastic band (SS-NEB) method employing double-climbing images (C2-NEB) combined with density-function theory (DFT+U) methods for accurate energetics, we detail the pressure-induced $α$ (ductile) to $ω$ (brittle) transformation at the coexistence pressure. We find two transition states along the minimal-enthalpy path (MEP) and discover a metastable body-centered orthorhombic (bco) structure, with stable phonons, a lower density than the endpoint phases, and decreasing stability with increasing pressure.

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N. A. Zarkevich, D. D. Johnson. 2015-12-29. Titanium $α- ω$ phase transformation pathway and a predicted metastable structure. https://doi.org/10.1103/physrevb.93.020104

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