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Flow behavior of many metals and alloys in the region of uniform plastic strain is normally expressed by the simple power law relationship (r = Ke p n ). 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 heattreated 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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