Scattering of elastic waves in simple and complex polycrystals

Shape effect of elongated grains on ultrasonic attenuation in polycrystalline materials.

Ultrasonic backscattering in polycrystals with elongated single phase and duplex microstructures.

In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.

Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data

The characterization and optimization of the microstructures of materials pertaining to material properties is a primitive necessity to ensure the performance and service life of the materials and components. In the demand of new characterization and evaluation techniques, nondestructive ultrasonic techniques have shown a good potential to characterize the microstructures and mechanical properties of a wide variety of materials. Measurements of ultrasonic parameters such as velocity and attenuation can provide information on the structural and microstructural variations of those materials that have undergone the heat-treatment procedure. In the current review, the correlation of ultrasonic parameters with microstructural features of ferrous and nonferrous metals such as steels, aluminum, and superalloys is investigated. It is proven that ultrasonic parameters are closely correlated to the microstructural evolutions which frequently occur during the heat-treatment procedures in practical situations. To conclude, the ultrasonic measurements contribute to a feasible and accurate characterization of the materials and evaluation of their microstructures and mechanical properties in a straightforward, reliable, and fast, nondestructive manner for practical applications.

On the correlation between microstructural evolution and ultrasonic properties: a review

A theory is presented for the ultrasonic backscattering in duplex microstructures. Assuming single scattering described by the Born approximation, we consider a microstructure consisting of macrograins containing colonies with crystallographically related orientations. General results are presented for the backscattering coefficient, assuming that all variants occur with equal probability. These are then applied to the particular case of titanium alloys, in which the macrograins are taken to be prior beta grains and the colonies are assumed to be alpha phase produced by a martensitic transformation. Numerical results illustrate the effects of ultrasonic frequency, colony size and ellipticity, and macrograin size and ellipticity on the backscattering.

Y. K. Han

Papers

Ultrasonic backscattering in duplex microstructures: Theory and application to titanium alloys