Shock-induced plasticity and interface intermixing mechanisms in nanolaminates with negative heat of mixing

Beyond the critical role of interfaces in plastic deformation behavior for metallic nanolaminates, interface intermixing has also been observed in experimental results. This phenomenon is strongly linked to the interface structure and the thermodynamic state during deformation, becoming even more significant in shock-adiabatic environments. Herein, Ni/Al nanolaminates with negative heat of mixing are selected to illustrate the plastic deformation and the deformation-induced interface intermixing after shock compression through atomic simulations, the size effect is also considered. As the bilayer thickness decreases, multiple reflections and transmissions drive the system to an equilibrium state faster. As the stress state surpasses the critical value, the misfit dislocation intersections serve as nucleation sites that preferentially promote dislocation nucleation in the Al layer, leading to localized disorder that facilitates dislocation nucleation in the Ni layer. During the plastic deformation at the interface, interface intermixing is activated. The release of shear stress results in the change in thermodynamic state and atomic arrangement. Nanolaminates with a thinner bilayer thickness require higher stress and temperature conditions to activate interface intermixing. This phenomenon can be explained by the higher shock stress resulting from the reflections and transmissions of the shock wave at the interface, which reduces atomic spacing and hinders intermixing. However, by facilitating a higher level of interface disorder, the continue interface intermixing is promoted. These findings reveal the activation condition for intermixing during plastic deformation under shock loading, offering valuable insights for microstructure design in future applications.