Diffusion behavior determined by the new n-body potential in highly immiscible W/Cu system through molecular dynamics simulations

Abstract

The excellent properties exhibited by W/Cu composites have stimulated the interest of many researchers. Molecular dynamics (MD) plays an important role in regulating the alloy ratio and exploring the microscopic mechanism. The accuracy of MD simulation depends on the reliability of the potential function. Here, we report a new W/Cu n-body potential. Compared with several existing potentials, the present potential can describe more precisely the lattice constant, cohesive energy and elastic constants (C11, C12 and C44) of W3Cu. On the basis of the new developed n-body potential, we have explored the diffusion behavior and the structure of the diffusion interface during the direct alloying occurring in the highly immiscible W/Cu system with MD simulation. The results of MD simulations show that the critical temperature of the diffusion and direct alloying between W and Cu is about 1000K. As the temperature increases, the diffusion flux of W/Cu diffusion increases while the interface structure becomes more disordered. The diffusion flux for W/Cu is greatest at the pressure of 150 MPa at pressures between 0 MPa and 300 MPa. The grain boundaries also have a great influence on the diffusion of W–Cu, with faster diffusion at the grain boundaries, and the Cu undergoes a phase change (ordered structure becomes disordered) when the interfacial stress of Cu reaches 1.7 GPa at a temperature of 662 K. In addition, the MD simulation results also show that the crystal plane orientations affect both the diffusion and heat conduction of W/Cu. The diffusion flux of W/Cu alloying is maximum when the crystal plane is W(111). The lattice thermal conductivity of the W/Cu interface is highest when the crystal plane orientation is W(100)/Cu(110).