Dissolved oxygen and the partial thermodynamic properties of γ′-Ni3Al + β-NiAl alloys

The effect of dissolved O on the solution behavior and phase transformations in γ′-Ni3Al + β-NiAl alloys was investigated by comparing the activities of Al, Al2O and Ni with the addition of Y, as Y2O3, to the Ni–Al–O system. In simple terms, this changed the stable oxide from Al2O3 (in Ni–Al–O) to YAlO3 (in Ni–Al–Y–O), and the activities of O and Al2O3 were reduced by about a factor of 5 and 100, respectively. There was, however, no observable change in the solution behavior or phase transformations of the Ni–Al phases.