Materials science

2) Preparation of microslicing. The microanalysis method is used to study the internal structure of metals and alloys with a microscope at a magnification of 50...1500 times. In 1883, the Russian scientist PPAnosov was the first to use a microscope for this purpose. As a result of inspection of the microgrind, it is possible to see the shape and location of cast metal or alloy grains, defects in them (cracks, slag inclusions, gas bubbles, voids, etc.).
A sample of a metal or alloy prepared for microanalysis is called a microsection .
Microslide is prepared as follows:
1 . With the help of metal chisels, square samples with sides of 10x15 mm or 15 mmcylindrical samples with a diameter of 10 and a height of 10-15 mm are cut;
2. One surface of the sample is smoothed (soft metals) or sharpened (steel, cast iron) with a special tool with small teeth;
3. Shimmering. This process is done to remove the marks left by ego or wheel on the surface of the sample.
4. The cleaned and flattened sample is first washed in water, then in alcohol or gasoline and dried. Then the sample is treated with a chemical reagent ( 4% solution of NNO _{3 in ethyl alcohol).}
5. After treatment with reagents, the sample is washed again with water, then alcohol or gasoline, and dried using filter paper. After that, the sample is ready for inspection.
The produced polishing papers are numbered as follows: 12, 10, 8, 6, 5, 4, 3, 2, 1 (the number indicates the size of the particles of the substance on the paper, in hundredths of a millimeter).
The grinding process begins with paper #12 and ends with paper #1. During grinding, it is important to turn the sample at an angle of 90 0 in order to eliminate the marks left by papers with different grain sizes with the next paper ^. should be processed.
If the sample heats up during grinding, it should be dipped in water and cooled, then wiped with a cloth, and then continued grinding.
Polishing of the polished surface is done to remove small lines on it. The surface of the polished sample takes on a shiny (mirror) color. To polish the sample, a woolen material is used, on the surface of which a mixture of aluminum or chromium oxides in water is applied, which rotates at a high speed in the polishing machine. Due to the high hardness of these oxides and their very small particles, they also remove irregularities on the surface of the sample.

Necessary equipment, materials and tools to perform the work : metal sample, metal chisel, chisels, grinding papers with different numbers, wheel, water container, rag, chemical reagents (2-5% solution of nitric acid in ethyl alcohol), MIM-7 metallographic microscope or magnifying glass.
Laboratory procedure:

1. 
   Selection of the sample taken for macro- and microslices;
   
2. 
   Grinding or sharpening, grinding and polishing the selected sample;
   
3. 
   Wash and dry the cleaned and leveled sample first in water, then in alcohol or gasoline, and treat the sample with a chemical reagent (4% solution of NNO _{3 in ethyl alcohol);}
   
4. 
   Check the readiness of the prepared microslide by observing it under a magnifying glass or microscope;
   

The following shall be included in the laboratory report:

1. 
   The intended purpose of the laboratory work;
   
2. 
   Understanding of macro- and microgrinding technology;
   
3. 
   A drawing of the macro- and microstructure of the sample;
   
4. 
   General conclusions.