Microstructure evolution and spallation of CoCrFeNi/Al multilayers subjected to shock loading

The role of interfaces in mediating wave attenuation, dislocation activity, and spalling is critical for the application of high-entropy alloy (HEA) multilayer films. In this work, bilayer, four-layered, and six-layered CoCrFeNi/Al multilayer models with semi-coherent interfaces were constructed via molecular dynamics (MD) simulations to systematically investigate the role of interfaces under shock loading. The results reveal that multilayer configurations significantly attenuate transmitted pressures through interfacial stress dissipation, while suppressing FCC-to-BCC transitions. The spallation resistance is found to scale non-monotonically with layer count: increased interfaces reduce damage via energy dissipation, yet thinner layers exacerbate localized tensile stresses, reflecting a competition between Hall-Petch strengthening and stress concentration effects. Furthermore, comparative analysis with pure Ni/Al multilayers reveals that interface misfit dislocations induced by the incorporation of HEA serve as active nucleation sources for Shockley partial dislocations and stacking fault pyramids, dynamically regulating defect propagation and phase stability. These insights establish a microstructure-property framework for designing HEA-based multilayers with tailored shock resistance.