Structure and mechanical properties of B2 ordered refractory AlNbTiVZrx (x=0-1.5) high-entropy alloys

Structure and mechanical properties of the AINbTiVZr(x) (x = 0; 0.1; 0.25; 0.5; 1; 1.5) refractory high-entropy alloys were investigated after arc melting and annealing at 1200 degrees C for 24 h. The AINbTiV alloy had a B2 ordered single phase structure. Alloying with Zr resulted in (i) change of the degree of order of the B2 phase; and (ii) precipitation of the Zr5Al5 and C14 Laves ZrAIV phases. The density of the AINbTiVZrx alloys varied from 5590 kg m(-3) for the AINbTiV alloy to 5870 kg m(-3) for the AlNbTiVZr1.5 alloy. The compression yield strength at 22 C increased with an increase in the Zr content from 1000 MPa for the AINbTiV alloy to 1535 MPa for the AlNbTiVZr1.5 alloy. The plasticity raised from 6% for the AINbTiV alloy to > 50% for the AlNbTiVZr0.5 alloy and then dropped to 0.4% for the AlNbTiVZr1.5 alloy. At 600 C, the strongest alloy was also the AlNbTiVZr1.5, whereas, at 800 C, the AlNbTiVZr0.1 alloy demonstrated the maximum strength. The plasticity of the AINbTiV alloy at 600 C increased up to 14.3%, while the Zr-containing alloys had lower plasticity. At 800 C, all the AINbTiVZrx alloys could be plastically deformed up to 50% of strain without fracture. Ordering in the alloys and the reasons of a complicated dependence of mechanical properties of the AINbTiVZrx alloys on the Zr content and temperature were discussed.