Effects of alloying elements on the Ni/Ni3Al interface strength and vacancy diffusion behavior

The effects of seven alloying elements (Co, Cr, Mo, Re, Ru, Ta, and W) on the Ni-vacancy diffusion behavior and the rupture strength of γ-Ni/γ′-Ni3Al interfaces are studied using density functional theory calculations. Our results reveal that all seven solutes prefer to occupy Al sites close to or Ni sites far from the interface. These solutes except for Co could significantly increase the barrier of Ni-vacancy diffusion within the γ/γ′ interface region. The retarding effects are similar when solutes are located at their favored Al and Ni sites, which follows the sequence of Ta > W > Mo > Re > Ru > Cr > Co. Besides, it is found that the presence of solute atoms could always increase the rupture strength of their neighboring interface but reduce that of their next neighboring interface. The best strengthening effects on the neighboring interface are achieved by Re and W. In terms of the entire interface region, alloying at the favored Al site brings a better strengthening effect than that at the favored Ni site. The charge density difference analysis demonstrates that the charge accumulation level at the interface explains the variable strengthening effects among different alloying elements.