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

Structure and mechanical properties of the AlNbTiVZrx (x = 0; 0.1; 0.25; 0.5; 1; 1.5) refractory high-entropy alloys were investigated after arc melting and annealing at 1200 °C for 24 h. The AlNbTiV 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 Zr5Al3 and C14 Laves ZrAlV phases. The density of the AlNbTiVZrx alloys varied from 5590 kg m−3 for the AlNbTiV 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 AlNbTiV alloy to 1535 MPa for the AlNbTiVZr1.5 alloy. The plasticity raised from 6% for the AlNbTiV 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 AlNbTiV alloy at 600 °C increased up to 14.3%, while the Zr-containing alloys had lower plasticity. At 800 °C, all the AlNbTiVZrx 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 AlNbTiVZrx alloys on the Zr content and temperature were discussed.