Effect of Al content on structure and mechanical properties of the AlxCrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys

Abstract

In present study, structure and mechanical properties of the AlxCrNbTiVZr (x=0; 0.25; 0.5; 1) high-entropy alloys after arc melting and annealing at 1200°C for 24h are investigated. The CrNbTiVZr alloy is composed of body centered cubic (bcc) and C15 (face centered cubic) Laves phases while the AlxCrNbTiVZr (x=0.25; 0.5; 1) alloys consist of bcc and two C14 (hexagonal close packed) Laves phases with different chemical compositions. Thermodynamic modeling predicts existence of two phases – bcc and C15 Laves phase and broadening of single bcc phase field due to Al addition. The density of the alloys decreases with the increase of Al content. The alloys are found to be extremely brittle at room temperature and 600°C. The alloys have high strength at temperatures of 800–1000°C. For example, yield strength at 800°C increases from 440MPa for the CrNbTiVZr alloy to 1250MPa for the AlCrNbTiVZr alloy. The experimental phase composition of the AlxCrNbTiVZr alloys is compared with predicted equilibrium phases and the factors governing the transformation of C15 to C14 Laves phases due to Al addition to the CrNbTiVZr alloy analyzed. Specific properties of the alloys are compared with other high-entropy alloys and commercial Ni-based superalloys.