Strengthening Cu/Ni nanolayered composites by introducing thin Ag interlayers: A molecular dynamics simulation study

Experiments have shown that the ultrahigh strength of nanolayered metallic composites originates from their high-density interfaces of special characteristics. Hence, the modulation of interface structures becomes an effective route to enhance the mechanical performance of the nanolayered composites. One of the general ways to tune the interfacial feature is to introduce interlayers of several nanometers among constituent layers, such as amorphous (disordered) and crystalline (ordered) interlayers. Here, the deformation of a Cu/Ni layered composite with Ag interlayers of different thicknesses was simulated by molecular dynamics simulations. Our simulations show that the yield stress of 25 nm Cu/25 nm Ni nanolayered composites with Ag interlayers can be significantly enhanced, i.e., it can be 56.4% higher than that of their counterparts without interlayers. We also found that the yield strength of the new composites can be maximized by selecting an appropriate thickness for the Ag interlayer. The optimum interlayer thickness is 2.1 nm in tension and 4.2 nm for compression. It is revealed that the extra strength results from the alleviation of stress concentration by stimulating abundant interfacial dislocations at the Cu–Ag and Ag–Ni interfaces. These findings show that the introduction of additional interlayers is a new route to design stronger nanolayered metallic composites.