Metal-matrix nanocomposites under compressive loading: Towards an understanding of how twinning formation can enhance their plastic deformation

Recently, Cu-Ag nanocomposites (NCs) have been extensively used as medical implants and surgical instruments due to their antibacterial properties. Consequently, mechanical behavior analysis of these NCs is of crucial importance with emphasis on their plastic deformation mechanisms. From the materials science perspective, dislocations slip at the room temperature and high strain rates conditions is hindered. However, copper and silver, as two metals with low stacking fault energy are prone to twin formation. Since microstructural changes in these nanostructured composites occur at the atomic scale, molecular dynamics (MD) simulation is undoubtedly a great tool to use. Accordingly, in the present research, first, the deformation mechanism of perfect copper-silver NCs under uniaxial compression is deeply analyzed employing MD. This is followed by inspection of the voids effect on their plastic deformation process. The results show that twinning is the dominant mechanism governing their deformation under uniaxial compressive loading conditions. It is revealed that twins are created by the conversion of internal stacking faults to their external counterparts. Also, investigation of the microstructural evolution demonstrates that the presence of voids within NC samples provides new sites for nucleation of Shockley dislocations in addition to the interface zone. Finally, to address the effect of interfacial coherency on the results, copper-based NCs infused with gold and nickel nanoparticles are also thoroughly examined.