Computational characterization of the structural and mechanical properties of AlxCoCrFeNiTi1−x high entropy alloys

Abstract

AlCoCrFeNiTi is one kind of high entropy alloys with potential applications in aerospace, electronics and machinery manufacturing, etc. Its microstructure, thermodynamic and mechanical properties vary with Al and Ti contents. The disordered structures of Al _x CoCrFeNiTi _1− _x ( x = 0–1.0) alloys were generated and screened with the special quasi-random method. First-principles calculations with the Perdew–Burke–Ernzerhof functional and projector-augmented wave potential were carried out to further identify the structures and assess their thermodynamic and mechanical properties. The measured lattice constants and observed phase transition from bcc to fcc with Ti addition and Al reduction were reproduced in the calculations. The predicted transition point is at the Al content of about 8 at%. The heat capacity of the bcc and fcc structures exhibit similar temperature dependence, matching well with the empirical Dulong-Petit Model and the quantum Debye Model. The elastic constants and elastic moduli vary with the phase structures and compositions. The studied Al _x CoCrFeNiTi _1− _x alloys are predicted to possess good comprehensive mechanical performances, especially for x = 0.8 and 0.6 for the bcc structures and x = 0.5 for the fcc structures. The addition/reduction of Al atoms from the systems alters the electron localization/delocalization that has considerable influence on the interatomic interaction strength in the alloy systems.

Keywords

• high entropy alloys
• first-principles calculation
• phase transformation
• thermodynamic stability
• mechanical properties