The alloying behaviour and mechanical properties of polycrystalline Ni3Al (γ′ phase) with ternary additions

A survey of the results from a variety of techniques has shown that the substitution behaviour of alloying additions is primarily determined by electronic considerations. Thus, Si, Ti, V, Mn, Nb, Hf and Ta substitute for aluminium; Co and Cu substitute for nickel and Cr, Fe, W, and Mo substitute for both species. A number of conclusions have been drawn from an analysis of compression test data, the most significant of which was that the mechanical properties of γ′ depended on both the substitution behaviour of the alloying addition and the degree of non-stoichiometry. Considerable strengthening is only obtained when (1) the alloying addition substitutes for aluminium and has a large size misfit parameter, and (2) the alloy is aluminium-rich or stoichiometric.