Abstract
In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. The mechanism of the directional coarsening of phases (rafting) of Ni-base superalloy under uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni_3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin film structure with the (001) face-centered cubic interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Palladium was one of the most effective elements which restrain Al atoms from moving around the interface under the applied stress.
