S. Ali Sadough Vanini  

Overview:

Materials science Lab. is one of the oldest Lab. in mechanical engineering higher education technical and engineering department. Materials science Lab started its activities since 1958 and over time expanded its size and quality in education and researches.

Research Focus/Goals:

• Materials Characterization
• Materials Science & Engineering
• Metallurgical & Materials Engineering Ceramic Engineering etc…

Involves establishing relationships between:

• Structures of materials
• Processing of materials
• Properties of materials
• Structure determines properties
• Properties can be changed by altering composition and/or processing

 Equipment (Experimental lab):

Metallographic and Materialographic Specimen; Preparation Systems; Light Microscopy; Image Analysis; Heat Treatment and Hardness Testing

Sample Preparation

Metallography:

• A systematic method to examine microstructure of Materials (mainly metallic materials).

• Can also be used to examine ceramics, polymers and semiconductors.

1- Sectioning

Why sectioning?

1. Size limitation of specimen to be examined under optical

microscope.

2. Locate area needs to be selected from a large sample.

2- Microtomy:

• Useful for preparing soft materials such as polymer samples.

• Steel, glass or diamond knives in a microtome can cut samples into very thin sections.

3- Grinding

1. Removes the damage from the surface produced by sectioning.

2. Grinding also produces damage which must be minimized by subsequent grinding with finer abrasives.

3. At the end of grinding phase, the only grinding damage present must be from the last grinding step.

4. Such damage will be removed by polishing. Grinding Materials: Abrasive paper (covered with silicon carbide grit).

Commonly a series of abrasive papers are used from coarse to fine.

Typical Grit Sequence: 120-, 240-, 320-, 400-, 600-, 1200-, 2400-, etc.

4- Polishing

After being ground to a 600-grit finish (or better), the sample is polished to produce a flat and scratch-free surface with high reflectivity.

Coarse polishing: abrasives in the range of 30 μm to ~3 μm using diamond grits of the appropriate size.

Fine polishing: abrasives in the range of 1μm or less using diamond grits of the appropriate size.

Final polishing: 0.25-0.05 μm diamond, silica, or alumina slurries.