Aluminum Alloy Sensitization Evaluation by Using Eddy Current Techniques Based on IGMR-Magnetometer Head

To control the quality of conductive materials such as copper, aluminum, or steel, various non-destructive testing techniques based on eddy current monitoring are routinely employed. Some marine alloys such as the Al-5000 series are the subject of interest notably in shipbuilding because of their good mechanical properties. However, this type of material is often subjected to intergranular corrosion and stress corrosion cracking when sensitized (i.e., after a regular increase in temperature). This paper deals with the evaluation of sensitization on an aluminum alloy by using an eddy current technique utilizing an improved giant magnetoresistance magnetometer as the head sensor. The magnetic field responses of different samples, which have been subjected to different heat treatments, are presented. The results are compared to an analytical model, which takes account of the setup and sample, in order to evaluate the material property evolution due to the sensitization. We show, clearly, that the given heat treatment (>175 °C) has induced a material conductivity variation.