Lab1CrystalStructureF06-1

Lab1CrystalStructureF06-1 - Laboratory 1 It's What's Inside...

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MatE 215 Lab 1: Crystal & Amorphous Structures (Fall 06) Page 1 of 14 Laboratory 1 It’s What’s Inside That Counts: Crystal Structures and Microstructures Goal: To investigate materials on the atomic level (i.e., unit cell) and to relate how the crystal structure affects properties on the macroscopic level. Learning Objectives: 1. Describe the different length scales associated with materials, and give appropriate measurements in terms of meters. 2. Explain how unit cells can represent crystalline materials. 3. Name common metals and ceramics and their applications based on their properties. 4. Describe how properties are derived from the crystal structure of materials 5. Draw and build unit cells of the BCC , FCC , and HCP crystal structures. 6. Derive geometrical relationships between the lattice constant ( a ) and atomic radius ( r ) of simple metallic structures. 7. Identify the crystallographic close packed direction and plane , and explain their significance. 8. Calculate the density of a metallic element based on the unit cell. 9. Define anisotropy. 10. Build the diamond cubic and simple ceramic crystal structures. 11. Give examples of allotropy , and how phase transformations might be used in engineering applications.
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MatE 215 Lab 1: Crystal & Amorphous Structures (Fall 06) Page 2 of 14 Figure 1 . Taken from The Science and Engineering of Materials , 4 th ed., Askeland and Phulé, 2003. S P P Performance
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MatE 215 Lab 1: Crystal & Amorphous Structures (Fall 06) Page 3 of 14 Across The Length Scales of Materials Materials are all around us, yet how much do we really appreciate what materials are made of? Why are there so many different types of materials? – hard, soft, strong, flexible, transparent, shiny, conducting, insulating, magnetic, etc. The particular traits or properties of materials can often be traced back to the types of atoms and how they are arranged. As Figures 1 and 2 depict, different length scales of materials reveal very different features. We are used to thinking about materials on the bulk or macroscopic level (~1 cm = 10 -2 m) since we can visually see objects on this scale with our own eyes. We can also use our other senses, such as touch or hearing, on the macroscale. However, at smaller length scales (or at higher magnifications with the use of microscopes), we enter the micron scale (~10 -6 m), or the microstructure . Much information about a material’s properties or history can be revealed at this level. In order to “see” the microstructures, special preparation (i.e., metallography ) is needed. A small piece of the material is sectioned and then usually mounted in bakelite or epoxy for handling purposes. The surface is then ground and polished in successive steps in order to achieve a very flat, mirror finish. Etching with chemicals is then often used to bring out certain features, such as
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Lab1CrystalStructureF06-1 - Laboratory 1 It's What's Inside...

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