Ni₈X phases in the systems Ni-V, Ni-V-Nb, and Ni-V-Ta

Abstract

In nickel-base alloys at the composition Ni₈X, where “X” may be combinations of V, Nb, and Ta, the ordering reactions have been investigated by employing electrical resistivity and electron diffraction techniques. The critical temperature for the order-disorder reaction is estimated to be 405° C for Ni₈V and is shown to decrease linearly with increasing vanadium content across the pseudo-binary sections Ni₈Nb-Ni₈V and Ni₈Ta-Ni₈V, in agreement with calculations based upon the Bragg-Williams model. A secondary ordering reaction between V and Nb atoms has been observed in nickel-base alloys at the composition Ni₈(V_0.5Nb_0.5).