Protective mechanism of high-entropy bulk metallic glass against hypervelocity impact

As an advanced bumper material, high-entropy bulk metallic glass (HE-BMG) exhibits excellent protective performance against hypervelocity impact (HVI). To comprehensively understand the protective mechanism of HE-BMG against HVI, based on the analysis of the effects of material properties on HVIs, numerical simulates of Al2024 spherical projectiles hypervelocity impacting on Al2024 and HE-BMG bumpers were conducted over a wide range of bumper areal densities (0.14–0.84 g/cm²) and impact velocities (2.5–6.5 km/s). The results were quantified using secondary development and self-compiled programs. Combined with experimental results and theoretical calculations, a detailed comparison was made between the two bumpers in terms of projectile and bumper materials fragmentation, dispersion, energy dissipation, and phase transition. The results demonstrate that the HE-BMG bumper is beneficial to increasing the shock pressure and promoting the failure and fragmentation of materials. Unlike the Al2024 bumper, which produce fragments more threatening than projectile upon shattering, the HE-BMG bumper debris cloud exhibits a more uniform and consistently lower load distribution on the rear wall. Moreover, the HE-BMG bumper can reduce the average velocity of the projectile debris cloud, increase its expansion velocity and spray half-angle, thereby increasing the impact area and decreasing the load density of the debris cloud acting on the rear wall. Finally, the HE-BMG bumper induces phase transitions in projectile and bumper materials at lower impact velocities, which helps reduce the penetration capability of the debris cloud to the rear wall.