Local characterization of materials using an impulse-SAM technique in the 10MHz-20MHz range

This paper deals with the material characterization by an impulse ultrasonic method, deriving from the Surface Acoustic Microscopy (S.A.M.). This pulse technique is especially proposed to investigate the subsurface area by means of the penetration depth of the Rayleigh waves, depending on the wavelength. A spherical (or cylindrical) shaped transducer is excited by a broadband pulse in the 10MHz-20MHz range. An accurate method for Rayleigh velocity measurement is developed (resolution of 0.6%). Then, velocity variations due to rolling texture (reduction rate of 50%) are measured and related to the elastic constants variations. The grain size effect on the Rayleigh wave velocity is also analyzed (10 mu m-100 mu m) and compared with success to the modeling taking into account the ultrasonic attenuation.