Laboratory Two: Processing - Structure-Property Relations

In order to examine and evaluate the structure of a material it is necessary to observe it under a microscope. This requires that the sample be extremely flat. The surface roughness has to be on the order of the wavelength of the light. As prepared specimens are not suitable for direct observation, the surface has to be prepared.

Process Steps (This should not be copied into the HW)

The three grades of steel examined last week will be subjected to metallographic examination in order to discern the structure and relate structure to properties and structure to processing.

Sample Preparation involves the following steps

• Cutting a small section of the material
• Mounting the sample in an epoxy mount to ensure ease of handling
• Grinding the sample on progressively finer sand paper. Rotate the sample 90 degrees each time to remove the previous set of scratches. Wash the sample before moving onto the next finer grit so that you do not embed larger particles onto finer sand paper.
• Washing the sample with soap and water, exposing to ethanol and drying after the 600 grit grind.
• Polishing on the diamond wheel until you can see your reflection
• Etching with Nital to expose surfaces. Remember atoms at interfaces have higher energy, they are underbonded and therefore will react faster
• Once the sample is properly prepared taking a micrograph.
• As a class we will use Google Drive to prepare a results sheet in Word

To assist you in organizing information for the homework the following data sheet is available.

This is for your use, it is not to be handed in with the homework.