IndexIntroductionTheoryErrors and precautionsConclusionObserve the constituents and structure of a piece of steel with the support of an optical microscope.Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Introduction Metallography is the study of the detailed microstructure of metal surfaces using an optical microscope or optical microscope. Some structures are visible to our naked eye and these are called macrostructures while the structures which are not visible to our naked eye and which need to be magnified to be observed are called microstructures. Microscopy is used for various purposes and one of its most important uses is to identify and learn about defects in metals, which is exactly what we have done in this laboratory experiment. We zoom in on these objects to examine their microstructures and conduct related studies. An optical microscope is sufficient for this experiment as it is not necessary to study details down to atomic resolution. Metals acquire different properties due to imperfections in their structure at the crystalline level. Microscopy can be used to obtain information regarding the composition of a metal, its property and many other details related to it. In this experiment we use an optical microscope to study the grains and grain boundaries of steel which is also a metal. The grain boundary is a transition region where some atoms are not exactly aligned with either grain. Microscopy can provide information mainly on: Grain size. Present phases. Chemical homogeneity. Present phases. Elongated structures formed by plastic deformation. Theory Since we need an understandable view of the microstructure, the sample must be handled with absolute care during preparation. For this purpose, it is necessary to follow some steps when preparing the sample for observation. To begin with, the surface of the sample is carefully sanded using a grinder with abrasive paper. Next, since the sample is rough, it is polished again to obtain a mirror surface, for this purpose the sample is held on a red velvet cloth on which diamond lapping paste is applied. After carrying out these steps, the sample is immersed in a solution of nitric acid with a concentration of 2% to 5%, in fact the maximum concentration of nitric acid that can be used is 50%. It is immersed in acid to remove the bits of impurity that would remain stuck to the sample after grinding and polishing it. On top of that, this brings the grains to the surface, which in turn makes our observation work much easier. Since the sample is now acidic and can react with air and form other impurities, it is then immersed in ethyl alcohol to neutralize it. Before it can be observed, the sample must be allowed to dry. Finally, an optical microscope is used to observe the grains. Materials and equipment: Piece of steel. Grinder and polisher. Red velvet cloth. Diamond paste for lapping. Optical microscope with magnification from 50x to 1000x. Nitric acid (2% concentration). Abrasive paper. Ethyl alcohol 99.9%. To begin with, a piece of steel sample of approximately 4 cm was already prepared at the beginning of the experiment. Subsequently, this sample was well ground using the grinder, it was in fact kept on an abrasive paper. While grinding, the speed was controlled via a knob. Additionally, water was added to prevent the sample from heating and also served as alubricant. This operation was performed for approximately 20 minutes, after which the sample was well ground. Subsequently, the sample was polished using a red velvet cloth which was in fact wrapped around a part of the grinder itself. Furthermore, diamond lapping paste was applied to the red velvet cloth to increase the efficiency of the polishing machine. Once again, the speed was controlled by the grinder knob. This was continued until a mirror-like surface was obtained. Subsequently, the sample was etched in a solution of nitric acid at a concentration of 2%. Subsequently, the sample was immersed in 99.9% ethyl alcohol. The sample was then left to dry for a few minutes. Finally, the sample was held under the microscope and visualized, the required photomicrograph was then obtained after which the calculations were performed. After completing all the above-mentioned steps, we could observe the view of grains and grain boundaries as we expected. Indeed, the grain boundaries were not as thick as we expected. The grain boundaries were irregular and the grain areas were sparse. Talking about the phases present in the microstructure, phases are regions at the atomic level that are homogeneous and separated from other similar regions by surfaces and have homogeneous properties exclusive to them. At a particular stage, the properties, composition and structure are indistinguishable. The phase change can occur due to the increase in temperature (but it also depends on other factors). Let's consider the phases present in the microstructure of steel which is precisely iron with 2% carbon. The main phases present in steel are as follows. Phase Austenite Allotriomorphic Ferrite Idiomorphic Ferrite Pearlite Ferrite Widmanstätten Upper Bainite Lower Bainite Acicular Ferrite Martensite Cementite Austenite is one of the phases of steel and has an FCC (face-centered cubic) structure. This exists at approximately 1150°C. When the temperature decreases, a phase change occurs. Austenite transforms into allotriomorphic and idiomorphic ferrite. Ferrite is stable at room temperature. In the meantime, cementite is also formed which is another phase. Cementite has drastically different properties than those possessed by ferrite. Pearlite is the result of the combination of the ferrite and cementite formed above. Martensite is formed when red-hot steel is rapidly cooled to a very low temperature. When austenite is cooled to an even lower temperature, bainite is formed, which is strong but ductile. Importance of Metallography Metallography is the study of the microstructure of metals. Today, a huge number of metals have been discovered that are used in our daily lives. The use of alloys and metals occupies an important place in engineering applications. Therefore, engineers are tasked with selecting the best metals for whatever they are modeling. They need to check whether the metals have been worked precisely. Most of these metals are opaque; these materials are observed with reflected light using microscopes at high magnifications. This is the main use of metallography. Metallography helps a metallographer to identify the properties and its composition. It can be used to identify their colors, grain sizes and even phases. It can help you keep track of the processes you have gone through up to that particular point. Furthermore, it is also possible to check the metal with regard to the alloy mixture. Therefore, metallography is of utmost importance to produce the best from the batch we have while improving the quality of already existing products. Please note: this is just a sample. Get one now.