Microscopic Boundary Examination :: essays research papers

MICROSCOPIC EXAMINATION OF METALSIn this experiment, our aim is examining the microstructure of metals. By studying microscopic structures of metals, we determine which material fits scoop out to a given application. We used the most common method, optical technique, to look the microstructure.We used a small specimen cut from the metal to be examined. To be able to see the structure clearly, we first cleaned and polished the specimen. graduation we start polishing with emery paper no 1 and some finer grades. One should be careful about the coarse abrasive particles and striations from them. change and rotating the specimen 90 during the transfer can prevent these. The next metre is polishing, yet washing the sample before polishing gives a much successful result. Finally, we polished the specimen on a rotating cloth cover with an effective abrasive like Al2O3-Water suspension. We kept polishing until we obtained a mirror like face.After we finished polishing, the crystalline structure of the specimen, any cracks, seams, non-metallic inclusions and inhomogenities, could be revealed. Before start etching we first applied rideing process. In this step we used a matched wear set. We placed our sample into the die set in the way that the rough face of the specimen was the turn down surface and the polished face looked upward. We filled the die cavity with Bakelite and because we transferred our die to a mounpress. Mounting not only protects our sample merely also by making its base flat and stable helps us while we are examining the sample under the microscope. In etching process, depending upon chemical composition, energy content and grain orientation, we determine the grain boundaries and the presence of chemically different phases. To reveal these micro structural details of the polished mount we used an etchant like 1% Nital.