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′-Ni 3 Al + β-NiAl alloys was investigated by comparing the activities of Al, Al 2 O and Ni with the addition of Y, as Y 2 O 3 , to the Ni–Al–O system. In simple terms, this changed the stable oxide from Al 2 O 3 (in Ni–Al–O) to YAlO 3 (in Ni–Al–Y–O), and the activities of O and Al 2 O 3 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.