Molecular dynamics simulation on deformation dynamics of Ni and Ni3Al single crystals and Ni/N4Al composite crystal

A molecular dynamics (MD) simulation of plastic deformation under a uniaxia l tensile strain condition for Ni (gamma) and Ni3Al (gamma') single crystal s and Ni/Ni3Al composite crystal with a (100) gamma/gamma' grain boundary i s performed. Simulations are performed at 298 and 1200 K using Finnis-Sincl air-type potentials. In the case of elastic deformation, the microscopic di splacement is equivalent to the macroscopic displacement. Within plastic de formation, the local atom-level displacement is not equal to the macroscopi cally defined displacement. The simulation results are analyzed from this v iewpoint using the number of atoms in the local neighboring configuration. The dislocation first forms at the surface and propagates the inside of the crystal on (111) planes. The dislocation speed reaches approximately half the sound velocity under the very high tensile stress condition. Dislocatio ns at elevated temperatures can propagate under lower stress than those at room temperature. However, the dislocation speed at elevated temperatures i s slower than that at room temperature. This effect is more noticeable for Ni,AI. The atoms on a slip plane move in the (110) or (211) direction. The dislocations become extended dislocations on the (111) plane for Ni and Ni, AI. The site potential energy is high at the slip plane crossing region. Th ere is no slowing of the dislocation propagation near the gamma/gamma' grai n boundary.