Abstract
Using first-principles calculations based on density functional theory, the elastic constants and some of the related physical quantities, such as the bulk, shear, and Young’s moduli, Poisson’s ratio, anisotropic factor, acoustic velocity, minimum thermal conductivity, and Debye temperature, are reported in this paper for the hexagonal intermetallic compound TiAl. The obtained results are well consistent with the available experimental and theoretical data. The effect of pressure on all studied parameters was investigated. By the mechanical stability criteria under isotropic pressure, it is predicted that the compound is mechanically unstable at pressures above 71.4 GPa. Its ductility, anisotropy, and Debye temperature are enhanced with pressure.
Highlights
Elastic constants are very important quantities to describe the mechanical properties of materials.They are and directly employed to evaluate the elastic strains or energies in materials under stress of various origins: external, internal, thermal, etc
To gain a deeper understanding of the high-pressure properties for Ti3 Al, in the present work, we focus on studying the elastic constants and some properties related to these constants for this compound in the range of 0–80 GPa by first-principles calculations based on density functional theory (DFT) and projector augmented wave (PAW) methods
Before calculating the elastic constants of the Ti3 Al intermetallic compound at a given pressure P, the unit cell of the compound at the corresponding pressure was optimized by full relaxation with respect to the volume, shape, and internal atomic positions until the atomic forces were less than 10−2 eV/Å
Summary
Elastic constants are very important quantities to describe the mechanical properties of materials. They are and directly employed to evaluate the elastic strains or energies in materials under stress of various origins: external, internal, thermal, etc. The plastic properties of materials are closely correlated with the shear moduli along the slip planes of mobile dislocations since these dislocations can dissociate into partials with a spacing determined by the balance between the planar fault energy and the repulsive elastic force [1]. Alloys based on the TiAl intermetallic compound with a good balance of higher strength and better ductility generally possess dual-phase lamellar structures composed mainly of the L10 -ordered tetragonal TiAl (γ) phase and a small amount of the hexagonal Ti3 Al (α2 ) phase [4]. The growing interest in dual-phase alloys further encourages our interest in the intermetallic compound Ti3 Al
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