Investigation of the microstructure of cast iron by laser ultrasonic surface wave spectroscopy

We have used an all-laser surface wave ultrasonic method to investigate cast iron samples with a variety of morphologies of included graphite precipitation. The relation between ultrasonic attenuation and the microstructure of cast iron is discussed. The frequency dependence of ultrasonic attenuation was obtained in a broad frequency band including the three characteristic regions of scattering. The scatterer size of the samples could be evaluated from the measurement, and good agreement was found between the average scatterer size estimated from our ultrasonic data and micrographic data. The demonstrated sensitivity of the ultrasonic propagation parameters to the microstructural properties of cast iron illustrates the strong potential of this technique for non-destructive microstructural characterization of polycrystalline materials.