Isothermal relaxation of the degree of long-range order, in homogeneous material that was doped with 0.19at%B, was studied by means of resistometry. It was found that 2 simultaneous relaxation processes were involved. These processes differed markedly in relaxation rate, but had similar activation energies of more than 4eV. A model was proposed which explained the occurrence of 2 parallel relaxation processes and was based upon vacancy thermodynamics in a L12 superstructure. The high activation energy which was deduced for long-range order kinetics was attributed to specific modes of vacancy diffusion that involved jumps between various sub-lattices. It was compared with the activation energies, for diffusion in Ni3Al, which were exhibited by ternary elements that occupied the Al sub-lattice. It was concluded that it was inadequate to relate Ni diffusion data to long-range order parameters for Ni3Al.

Kinetics of Defect Recovery and Long-Range Ordering in Ni3Al+B - II. Atomic Jump Processes Studied by "Order-Order" Relaxation Experiments. Kozubski, R., Pfeiler, W.: Acta Materialia, 1996, 44[4], 1573-9