Molecular dynamics simulation on elastic behavior of Ni/Ni₃Al interface with graded structure

The basic concept of the functionally graded material (FGM) is an active control of the structure of materials to be suitable for the object properties. This concept should be expanded to the atomistic level. In the present report, this idea is applied to the Ni (γ)/Ni₃Al(γ′) (100) interface. Molecular dynamics simulation is performed to clarify the correlation between the atomistic structure of the interface and the microscopic elastic properties. The Ni-Al binary 64000 atom systems with the FGM and NFGM type interface structures are simulated at 298 K with Finnis-Sinclair potential. The spatial local distribution of the lattice constant, the site potential energies and the atomistic stress energies are analyzed under the strain free condition. The global and local changes of these properties are calculated for various elastic tensile conditions. The lattice constant misfit and the stress concentration at the interface is weakened by the application of the graded structure to the γ/γ′ interface. Under the elastic tensile condition, the stress gap at the interface is proportional to the tensile strain for the standard (NFGM) interface. On the other hand, in the FGM structural interface, such an increase of the stress gap is not observed. The atom level graded structure is certified to be effective to reduce the stress at the interfaces under elastic deformation conditions.