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Figure 15
Ni-based binary systems with some alloying elements of interest in superalloy design; [\Delta\varphi] = [({\varphi}_{A}][{\varphi}_{B})] and [\Delta{N}^{1/3}] = (NA1/3NB1/3) , where Ni is the element A. We observe that those binary systems in which L12 (AuCu3-type) compounds occur at the composition A3B occur in a particular region (shaded) of the map. The Ni–Co system, being close to the origin, has low energy in the Ni–Co (atom-pair) bonds and there are no ordered compounds in the system. Ni3Fe is an L12 compound close to the origin; it has a lower ordering temperature of 790 K in comparison with the other L12 compounds. The morphology of the AuCu3-type precipitates in the Ni matrix of superalloys is determined by the mismatch in their lattice parameters with respect to the Ni matrix (Jena & Chaturvedi, 1984BB8). The lattice parameters of the L12 compounds can be deduced from Fig. 10[link].

ISSN: 2053-2733
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