Ultrasonic attenuation during the martensitic transformation in Cu-Zn-Al shape-memory alloys measured by a broad-band pulse-echo technique

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Abstract
Ultrasonic attenuation during the martensitic transformation of Cu-Zn-Al alloys has been measured by means of a broad-band pulse-echo technique. A different behaviour has been found in the attenuation against temperature for single crystals and polycrystalline samples; these differences have been explained by taking account of the scattering mechanisms. It has also been observed that surface effects play a very important role in determining the overall attenuation; they produce an ultrasonic peak when the attenuation in the bulk of the material evolves differently from the losses at the surface. Finally, the results obtained have shown that, in single crystals, the ultrasonic attenuation is not proportional to the transformed fraction of the sample.