Outstanding shear resistance in a low-density refractory Ti₃NbVAl high-entropy alloy subjected to dynamic loading

The mechanical property of a low-density refractory Ti₃NbVAl high-entropy alloy (HEA) with an ordered B₂ structure is investigated in the dynamic regime. The yield strength increased from 751 MPa at a strain rate of 10^–3 s^-1 to 1,400 MPa at a strain rate of ∼ 10³ s^-1, indicating an extraordinary strain-rate-hardening capability. Dynamic compression of the hat-shaped sample suggests that it also exhibits excellent shear resistance under a deviatoric strain rate of 10⁵ s^-1, which resists the adiabatic shear-band formation at a large imposed shear strain of ∼16. The microstructure inside the shear bands shows that a severe grain refinement combined with a B₂ to body-centered-cubic (BCC) crystal structure transition occurred during shear localization. Our results demonstrate that the Ti₃NbVAl HEA exhibits great toughness under dynamic-loading conditions. An excellent load-bearing capacity under high-strain rate loading conditions leads to its promising applications in aerospace, transportation, and energy.