Energy dissipation and structural tuning mechanism of bicontinuous nanoporous metallic glasses under shock loading

Bicontinuous nanoporous metallic glasses (BNPMGs) combine ultralow density with outstanding shockwave mitigation capability, yet the mechanisms governing their energy dissipation under impact remain poorly resolved. Here, molecular dynamics simulations are performed to uncover the deformation and energy dissipation mechanism of BNPMGs subjected to 300 − 850 m/s impact velocities. Porosification is shown to increase the intrinsic energy dissipation per atom by up to 11 times, enabled by extended plastic flow and enhanced thermomechanical conversion. By decoupling the energy pathways, we quantitatively partition the dissipated work into strain, thermal, and surface contributions, revealing the dominant role of thermal conversion and a negative surface energy term associated with interface collapse. Notably, we discovered a stress-driven transition in deformation modes within the critical velocity regime, characterized by a shift from velocity-mismatch shear to boundary-release crushing. Parametric studies of solid fraction and ligament diameter show that structural parameters regulate temperature rise efficiency by controlling peak stress and local strain gradients. Consequently, a solid fraction of 65% yields optimal volumetric energy dissipation, resulting from the competition between temperature rise efficiency and material compressibility. These findings advance the fundamental understanding of energy dissipation in bicontinuous nanoporous metals under extreme conditions, providing critical design guidelines for impact protection applications.