Abstract: Premature adiabatic shear localization caused by strain softening is a roadblock for the application of body-centered cubic (BCC) structured high-entropy alloy (HEAs) in the impact field. A micron-scale orthorhombic-phase (O-phase) strengthened TiZrVNbAl alloy was developed to delay adiabatic shear failure and enhance dynamic ductility. The O-phase can not only reduce the slip length, but also promote the pinning and tangling of the dislocations near the phase boundaries. The introduction of the O-phase transformed the strain hardening rate from negative to positive, resulting in a significantly improved dynamic shear resistance. Meanwhile, slip transfer across the O-phase via dislocation cutting mechanisms and a reduction of slip band spacing guaranteed dynamic deformation uniformity. Benefiting from the introduction of the O-phase, the alloy exhibits an excellent stored energy density (∼446 J/cm³, surpass the reported BCC-HEAs and typical titanium alloys), a large dynamic fracture strain (∼42 %) and a considerable dynamic specific yield strength (∼241 MPa cm³ g^-1). The present study presents an effective approach for developing BCC-HEAs with excellent dynamic shear resistance and plasticity.

Key words: Multicomponent alloy, Orthorhombic-phase, Shear resistance, Adiabatic shear band, Dynamic deformation mechanism