Optical Metallography with a Laser Beam: Orientation Dependence of the Dispersed Intensity F. Povolo,** E. Favret,* and A. Canzian* *Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Dto. de Ffsica, Pabellfn l, Ciudad Universitaria, (1428) Buenos Aires, Argentina; ~-Comisifn Nacional de Energfa At6mica, Dto. de Ciencia de los Materiales, Av. del Libertador 8250, (1429) Buenos Aires, Argentina 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 micro- graphs obtained are compared with those produced under normal (white) light. As pre- viously 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. INTRODUCTION the objective of the microscope when the lines left by the polishing (which are par- Observations of the surface of some po- allel) are perpendicular to the trajectories lycrystalline hexagonal metals and alloys, of the laser beam. Moreover, the lines left conducted with the use of an optical mi- by the mechanical polishing change direc- croscope illuminated with a laser beam, tion from one grain to the other. have been reported recently [1]. Both nor- It is the purpose of this article to report real and oblique incidence of the laser some new observations in cubic metals, to- beam on the surface of the specimens were gether with a study of the orientation de- employed, and the micrographs obtained pendence of the dispersed intensity, for were compared with those produced oblique incidence of the laser beam on the under normal (white) light. These obser- surface of the specimen. vations, performed in zinc, zirconium, and zirconium-tin, have shown that by illu- RESULTS minating with a laser beam at oblique in- cidence, it is possible to reveal grain CUBIC METALS boundaries at an earlier stage of the spec- imen etching than by illuminating with All specimens were mechanically polished white light. In addition, on a specimen that down to 600 emery paper. A solution with has been polished only by mechanical 10 mL of H2SO4, 5 mL of HF, and 85 mL means, a higher intensity was obtained in of distilled water was further used for 137 ©Elsevier Science Publishing Co., Inc., 1991 MATERIALS CHARACTERIZATION 26:137 142 (1991) 655 Avenue of the Americas, New York, NY 10010 1044 5803:9153.50