Reaction triads, in which Mo layers of various thickness were sandwiched between Ni and Cu discs, were annealed in an inert atmosphere at between 950 and 1050C for times ranging from 5 to 300h. Parabolic growth of the NiMo intermetallic phase was observed at 1000 and 1050C. The Mo and NiMo layers acted as barriers to interdiffusion in the Ni-Cu system. When the growing NiMo phase reached the Mo/Cu interface, the phase transformed into a Mo-rich solid solution and a Ni-Cu solid solution. The diffusion barrier was then no longer effective. The interdiffusion coefficient was deduced, from the behavior of the Ni/Mo couples, by using the Boltzmann-Matano method. It was found that the interdiffusion coefficient for the α-phase at 1050C was equal to between 4.9 x 10-16 and 2.1 x 10-15m2/s.

Y.Shueh, J.P.Hirth, R.A.Rapp: Metallurgical Transactions A, 1991, 22[7], 1501-10