Full-field infrared phase sensitive thermography for microstructural investigation of giant magnetostrictive materials

Background: Giant magnetostrictive materials are increasingly proposed for smart material applications such as in sensors, actuators, and energy harvesting applications. However, reviewing the literature on this topic, the reader observes a large amount of variability in the reported properties that are typically generated from overall strain or point-value strain measurements obtained with strain gages using the far field estimate to project the internal magnetic field in the specimen. Methods: A full-field phase-sensitive thermography method is proposed to correlate the full-field infrared measurements to changes in the microstructure induced by a cyclic magnetic field in a giant magnetostrictive alloy material. Results: The results show the potential of the proposed method in rapidly uncovering the effects of geometry and defects on the magnetostrictive response. The results show responses at the microstructure level from both magnetocaloric and magnetostrictive effects. Conclusions: The effects of the magnetostrictive material’s microstructural spatial variability and the specimen geometry on the localized magnetostrictive response warrant serious considerations but so far have not received significant attention. The method proposed is capable of highlighting magneto-elastic coupling in the composite specimens using the cycle magnetic field.