Phase transformations in an Ni-7.5 wt % al alloy

The structure of the Ni-7.5 wt % Al alloy subjected to heat treatment for various times at a temperature of 700, 1000, 1200, and 1300°C followed by water cooling is studied by transmission electron microscopy and electron diffraction. An ordering-separation phase transition is shown to occur in the alloy at a temperature slightly above 1200°C. As a result of this transition, the microstructure formed at 1300°C due to separation dissolves, and chemical compound Ni₃Al particles form as a result of a tendency toward ordering.