Shock wave propagation and spall failure of nanocrystalline Cu/Ta alloys: Effect of Ta in solid-solution

The role of the concentration and distribution of the Ta solute in a solid solution in the shock response and spall failure of a bulk nanocrystalline Cu (nc-Cu) system is investigated using large scale molecular dynamics (MD) simulations. The nanocrystalline Cu/Ta (nc-Cu/Ta) microstructures comprise a 16 nm grain size Cu matrix with distributions of 3.0%, 6.3%, and 10.0% Ta atoms either along the grain boundary or randomly in the Cu matrix. The shock response is investigated by identifying the modifications in the dynamic evolution of defect structures (dislocation nucleation and interactions), as well as the nucleation and evolution of voids. The MD simulations reveal the complex role of Ta in altering the spall behavior of the nc-Cu system. The presence of Ta is observed to improve the spall strengths of the nc-Cu system, and the strengthening behavior is achieved by limiting the capability to nucleate dislocations during shock compression and under tensile pressures. The highest values for spall strength are observed for a random distribution of Ta at a concentration of 6.3% Ta. While the increase in strength for a 16 nm grain sized nc-Cu system is reported to be similar to 8%, the role of the Ta solute is observed to be more pronounced at a larger grain size of 30 nm with a similar to 15% increase in the spall strength for randomly distributed Ta with a concentration of 6.3%. The links between the concentration and the distribution of Ta in the solid solution and the evolution of microstructures under shock loading conditions are discussed. Published by AIP Publishing.