A first-principles study of interstitial oxygen on the strength/ductility of α-Ti: Crystal structures, elastic properties and electronic structures

Abstract

Interstitial oxygen (O) is one of the most critical impurity elements for titanium (Ti) and its alloys. This study adopts the first-principles method based on the density function theory (DFT) to calculate the lattice constants, elastic properties and electronic structures of the pure Ti and Ti-O(O) structures with different O contents. Results show that the c/a lattice parameter increases with the increase of O content and reaches the maximum value of 1.642 when O content is 20 at%. In addition, the bulk modulus (B), shear modulus (G) and G/B of the Ti-O(O) structures gradually increase with the increase of O content, and the corresponding ductility becomes worse. Furthermore, interstitial O atom makes a uniform transformation of the metal bond shift toward a more covalent direction, which strongly influences the ductility of Ti-O(O) structures. Furthermore, the interstitial O leads to the great difference in the chemical bond behavior of the crystals in different directions, which shows anisotropy on the micro level. The aim of this study is to reveal the effect of interstitial O on the mechanical properties of Ti alloys, and also to provide reference for reasonable control of O content of Ti alloys in industrial production.