MatSci%20201%20HW5%202008

MatSci%20201%20HW5%202008 - water (density of water = 62.4...

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MatSci 201: Introduction to Materials Homework #5: Due Monday, November 3, 2008 by 5 PM Submit in class or in the hanging folder outside 3035 Cook Hall No late homework accepted. Diffusion and Phase Diagrams 1. Callister, Question 5.6 2. Callister, Question 5.14 3. Callister, Question 5.30 4. You are given three aluminum samples of the same purity: single crystal, polycrystal with an average grain size of 10 microns, and polycrystal with an average grain size of 1 micron. Now you are to measure the self-diffusion coefficient (i.e., diffusion of aluminum atoms in aluminum) for each of these three samples at the same temperature. Rank the three diffusion coefficients. Explain how you arrive at this conclusion. 5. A certain town in the Midwest has 60 miles of roadway, with an average width of 50 ft. Assuming that NaCl is to be used for melting the snow, estimate how much salt should be used to handle a six-inch snow event. For the purpose of this estimate, you may assume that the density of snow is equal to 10% of liquid
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Unformatted text preview: water (density of water = 62.4 lbs/ft 3 ) and that the ambient temperature is around 20 F. This calculation shows why snowplows are always needed. 6. Go to http://www.doitpoms.ac.uk/miclib/phase_diagrams.php?id=3 to view an interactive version of the phase diagram for aluminum and silicon. (a) What are the eutectic temperature and the eutectic composition? (b) What does the shape of this phase diagram tell you about the solid solubility of Al in Si (e.g. completely miscible, partially miscible, completely immiscible)? Of Si in Al? (c) What is the maximum solubility of Al in Si at 500 C? (d) What is the maximum solubility of Si in Al at 500 C? (e) For an alloy with a composition of 5 wt.% Si, list the phases present, the composition of each phase and the weight fraction of each phase at 700, 600 and 400 C. Draw a sketch of each microstructure. 7. Callister, Question 9.44...
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