Work-Hardening Behavior of the Ni-Fe Based Superalloy IN718

Flow behavior of many metals and alloys in the region of uniform plastic strain is normally expressed by the simple power law relationship (σ = Kεpn). However, deviations have been observed from such behavior in several fcc metallic materials with low stacking fault energy. The age-hardenable nickel-iron base superalloy IN718 is also observed not to obey the simple power law relationship either in the solution treated as well as in the different age-hardened conditions. Various flow relationships were used to obtain the best fit for the experimental data, and different relationships were identified for the different heat-treated conditions. Detailed transmission electron microscopy (TEM) examination of the tensile-tested samples, interrupted after different amounts of strain, revealed inhomogeneous deformation by planar slip in all the heat-treated conditions. Cold rolling, however, was found effective in eliminating the unusual plastic flow behavior, observed in the as-heat-treated conditions.

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