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(V0.5Nb0.5).