Abstract:

Some observations of the surface of polycrystalline aluminum and nickel, conducted with the use of an optical microscope illuminated with a laser beam, are reported. Oblique incidence of the laser beam on the surface of the specimen is employed and the micrographs obtained are compared with those produced under normal (white) light. As previously observed in hexagonal metals and alloys, it is shown that by illuminating with a laser beam, it is possible to reveal grain boundaries at an earlier stage of the specimen etching than by illuminating with white light. A study of the variation in the intensity of the light dispersed by the surface of the specimen, under oblique illumination with the laser beam, as a function of the angle of rotation of the specimen around an axis perpendicular to its surface, shows that maxima and minima are present. These maxima and minima depend on the crystalline structure and the orientation of each individual grain in the polycrystal. © 1991.