Scanning acoustic microscopy and its applications to material characterization

The scanning acoustic microscope is a powerful new tool for the study of the physical properties of materials and has been successfully used for imaging interior structures and for nondestructive evaluation in materials science and biology. Its principles of operation, resolution, penetration ability, and contrast mechanisms are simply described in this paper. Recent progress in the application of acoustic microscopy to material characterization in solid materials is summarized. The experimental elastic microanalysis of bulk materials is carried out by measuring $V\left(z\right)\mathrm{}$, which includes examining the reflectance function of solid material, measuring the phase velocity and attenuation of leaky surface acoustic waves at the liquid-specimen boundary, and determining the elastic constants of the material. The layer thickness and mechanical properties of layered solids are studied by examining the dispersion properties of surface acoustic waves. A knowledge of the propagation properties of acoustic waves on the surface of materials is essential for understanding the contrast mechanisms and quantitative measurements in acoustic microscopy; these propagation properties are thus also briefly described in this paper. Finally, further developments of the scanning acoustic microscope aimed at improving its performance for quantitative evaluation are presented. These could expand the scope of the acoustic microscope as a diagnostic tool in many areas of science and technology.