A systematic investigation is being carried out to evaluate and model the effects of chemistry, heat treatment, and plastic deformation on the electrical resistivity of an IN718 alloy, to help calibrate an eddy current methodology of measuring resisdual stresses in turbine disk components.  The alloy was procured in different heat treated conditions with different hardness levels to determine the effect of prior-heat treatments.  Investigation showed that the eddy current spectra of the shot-peened alloy transitions gradually from a "normal" behavior to "abnormal" behavior as hardness increases.  Microstructural differences accompany this transition.  To better undersand the origins of this behavior, samples from selected heat treat conditions were uniformly deformed at room temperature to different levels of cold work.  These samples were then annealed for 1hr at different temperatures representing service temperature range.  The attendant changes in electrical resistivity and microstructures were followed.  A predictive model for the effect of microstructure on electrical resisitvity was developed.  The experimental results are analyzed using the model framework to separate the relative effects of each microstructural variable on the electrical resistivity.  The experimental results will be fit to analytical models (to extract unknown variables in the model) for use in calibrating eddy current methods for measuring residual stress in shot-peened or LPB treated engine parts.  The status of our understanding of the mechanisms will be presented in this talk.