Effect of Impurities on the Formation Energy of Point Defects in the γ-TiAl Alloy

• Published in: Journal of experimental and theoretical physics Vol. 127; no. 6; pp. 1046 - 1058
• Main Authors: Bakulin, A. V., Kulkova, S. E.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2018; Springer Nature B.V
• Subjects: Alloys; ALUMINIUM COMPOUNDS; Aluminum; APPROXIMATIONS; BINARY ALLOY SYSTEMS; CHEMICAL BONDS; Classical and Quantum Gravitation; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DENSITY FUNCTIONAL METHOD; Density functional theory; Disorder; Elementary Particles; Energy; Energy of formation; Free energy; Heat of formation; IMPURITIES; Intermetallic compounds; Lattices (mathematics); Modulus of elasticity; Molybdenum; Niobium; Order; Organic chemistry; Particle and Nuclear Physics; Phase Transition in Condensed System; Physics; Physics and Astronomy; POINT DEFECTS; Quantum Field Theory; Relativity Theory; Solid State Physics; Subgroups; Titanium; Titanium aluminides; Titanium base alloys; TITANIUM COMPOUNDS; Vacancies
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776118120130

The projector augmented-wave method within density functional theory is used to study the effect of 4 d elements and Group IIIA and IVA elements on the energetics of point defect formation and elastic moduli of the γ-TiAl alloy. To calculate the point defect formation energy, the grand canonical formalism was used. It is shown that the formation energy of aluminum vacancies decreases by approximately 1.3 eV with increasing its content in the series of alloys Ti 3 Al–TiAl–TiAl 3 , whereas the formation energy of titanium vacancies changes insignificantly. In general, the formation of titanium vacancies in these alloys is preferred to the formation of aluminum vacancies. It has been found that Nb, Mo, Tc, Ru, Rh, and Pd impurities on the aluminum sublattice contribute to an increase in the formation energy of an aluminum vacancies, and Mo and Tc also lead to an increase in the formation energy of titanium vacancies. All 4 d impurities, if they substitute for titanium, reduce the formation energy of aluminum vacancies, and Nb and Mo are favorable for increasing the formation energy of titanium vacancies. The influence of impurities on the chemical bond in the γ-TiAl alloy and its elastic moduli and characteristics based on them is discussed.