lab2 - Intro The Purpose of this experiment was to work a...

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Intro The Purpose of this experiment was to work a material such as brass so that the microstructure was revealed. The microstructure was revealed by thermal-mechanical processing and the relationship between hardness and grain size was determined. The thermal-mechanical processing showed the defects of the microstructure i.e. grain boundaries, twins, and slip dislocations. Decreasing grain size reduces the defects and increases the hardness of the material. Procedure The hardness of a sample of material (brass) was measured using the Rockwell Hardness method. The brass sample was placed on the machine and tested on the F scale 3 separate times making sure each indent was away from each other and the edge. The average of the three tests was written on the back of the sample. Then, given an eproxy mounted sample of know hardness, the grain size was determined. The sample was filed down by wet silicon carbide paper of different crystal size. The sample was filed on each paper perpendicular to the scratch lines until the lines were in the direction of the filing. After polishing on the silicon carbide paper, the sample was buffed with different samples of alumina slurry on rotating wheels. Each station was for 5 min or until lines could no longer be seen on the sample. The sample was washed with water so as not to transfer the different size crystals to the different wheels. The pad had to kept wet or the sample would be ruined. After polishing with the smallest alumina crystals, the sample had no scratches and was electropolished in a solution of 33% nitric acid and 67% methanol at 0 o C and 8 volts for 10 seconds. The grains were exposed by
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etching with a solution of hydrogen peroxide and ammonium hydroxide. An image of the
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This lab report was uploaded on 04/07/2008 for the course MSE 150 taught by Professor Wittig during the Spring '07 term at Vanderbilt.

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lab2 - Intro The Purpose of this experiment was to work a...

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