Chemical Activities in the Solid Solution of Hf in Ni₃Al

Abstract

Abstract The vaporization of the alloy samples of the compositions (Ni 3 Al) 1‐ x Hf x , x = 0, 0.010, 0.030, 0.052, 0.070, 0.089, and 0.100, as well as Ni 0.75 Al 0.25‐ x Hf x , x = 0.020, 0.040, 0.060, 0.080, and 0.100, was investigated at temperatures between 1361 and 1680 K in order to obtain information on the chemical bond in the solid solution of the γ' phase of the type Ni 3 Al. The partial pressures of Ni and Al were determined by calibration with pure nickel. Chemical activities and excess chemical potentials were evaluated for the solid alloys below the temperature of incipient melting and also in part for the melt. The excess chemical potentials obtained for the γ' phase indicate the substitution of Hf for Al in the γ' or Ni 3 Al phase.