Characterization of microtexture regions in Ti alloys using eddy current testing

Abstract

Microtexture region (MTR) formation in engine components made from titanium alloys has been shown to significantly reduce the dwell fatigue life of the components. Specifically, when the MTR is large enough and the c-axis is oriented in a specific direction relative to the loading axis, cracks in MTRs can grow much more rapidly than predicted by traditional fracture mechanics. It has been shown that eddy current methods are sensitive to MTR formation on a bulk scale, but no study has been done to assess the fundamental limitations of eddy current methods for detecting specific MTRs. In this work, the sensitivity of eddy current sensors to MTRs at specific orientations with respect to the surface area and the volumetric depths was analyzed in a modeling and simulation framework. One MTR in a host of otherwise randomly oriented single crystals was simulated, varying the size and orientation parameters. The eddy current signals were predicted using a previously developed approximation based model. Both reflection differential as well as absolute coils were analyzed in this work.