Molecular dynamics simulation of Au-Ag nanowires under tensile loading

With the progress of nanotechnology, the application of functionally gradient materials (FGMs) has shifted from traditional applications to complex micro nano electronic and energy conversion devices. Therefore, it is very important to study the mechanics of different FGMs nanostructures for exploring the feasibility of their different applications. In this study, we used molecular dynamics (MD) simulation to study the mechanical properties of Au-Ag functionally graded nanowires (NWs) with radial gradient distribution. For the FGMs NWs considered, the radial distribution of Au-Ag alloy follows power function, exponential function and S-shaped function. Our results show that the distribution function parameters play an important role in adjusting the mechanical properties (elastic modulus and ultimate tensile strength) of FGMs. The study also shows that the power function and exponential function have a great influence on the mechanical properties of materials, and the S-shaped function has a relatively small influence than the other two functions. In addition, we found that the time to reach the peak value of total dislocation length lags behind the time to reach the ultimate tensile strength, and the dislocation density is unevenly distributed throughout the system. In the subsequent process of dislocation annihilation, the dislocation annihilation is more obvious in the region with higher dislocation density. Moreover, we consider the effect of strain rate on the crystal structure change of FGMs NWs. At low strain rate, the transformation of crystal structure type is reversible. With the increase of strain rate, this reversible trend gradually decreases until reversible change phenomenon no longer occurs.