Experiment_08-Metallography_Specimen_Preparation_and_Examination

Experiment_08-Metallography_Specimen_Preparation_and_Examination

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ME 3701, Materials of Engineering, LSU 1 Experiment: Metallography Specimen Preparation and Examination Objectives 1. To learn and to gain experience in the preparation of metallographic specimens. 2. To examine and analyze the microstructures of metals and metallic alloys. Abstract Proper preparation of metallographic specimens to determine microstructure and content requires that a rigid step-by-step process be followed. In sequence, the steps include sectioning, mounting, course grinding, fine grinding, polishing, etching and microscopic examination. Specimens must be kept clean and preparation procedure carefully followed in order to reveal accurate microstructures. Each student will prepare and examine a brass, steel or aluminium sample for metallographic examination. Additionally, a brass, steel or aluminiumsample with different composition, a eutectoid steel sample and a eutectoid Pb-Sn sample will be examined under the metallographic microscope. Photographs will be taken of the samples and the ASTM grain size number determined for each of the specimens if applicable. Background Metallography consists of the study of the constitution and structure of metals and alloys. Much can be learned through specimen examination with the naked eye, but more refined techniques require magnification and preparation of the material's surface. Optical microscopy is sufficient for general purpose examination; advanced examination and research laboratories often contain electron microscopes (SEM and TEM), x-ray and electron diffractometers and possibly other scanning devices. Incorrect techniques in preparing a sample may result in altering the true microstructure and will most likely lead to erroneous conclusions. It necessarily follows that the microstructure should not be altered. Hot or cold working can occur during the specimen preparation process if the metallurgist is not careful. Expertise at the methods employed to produce high-quality metallographic samples requires training and practice. The basic techniques can be learned through patient persistence in a matter of hours. This module takes the student through the metallographic sample preparation process step-by-step with demonstrations and explanations of sectioning, mounting, course & fine grinding, polishing, etching and microscopic examination. Sectioning Operations such as shearing produce severe cold work, which can alter the microstructure of a sample. Abrasive cutting (sectioning) offers the best solution to eliminate these undesirable features; the resultant
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This note was uploaded on 03/08/2011 for the course ME 3701 taught by Professor Moldovan during the Spring '11 term at LSU.

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Experiment_08-Metallography_Specimen_Preparation_and_Examination

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