ACOUSTIC MICROSCOfY FOR MATERIALS CHARACTERIZATION

An acoustic microscope with mechanical scanning and piezoelectric film transducers for the input and output has been developed for the microscopic examination of materials.1 In the reflection mode it is pos-sible to work with an acoustic wavelength of 0.5 micrometers and a resolution that compares to that of the optical microscope. The elastic images of material surfaces as recorded with this instrument display in-teresting features which provide information which complements the optical microscope. In particular we find that different phases show up with good contrast and in alloy material the texture of the grains can be recorded since the grain orientation influences the acoustic reflectivity. THE SCANNING PRINCIPLE With conventional microscopes it is common to view the entire field of view with one setting of the controls. The image appears either on the ret-ina of the observer, on photographic film or on a fluorescent screen. With acoustic radiation there is no available method for recor~ing the ent·ir