材料物理导论次作业题.docVIP

Homework one（2012-4-27） 1. The number of vacancies in some hypothetical metal increases by a factor of 5 when the temperature is increased from 1070 K to 1180 K. Calculate the energy for vacancy formation (in J/mol) assuming that the density of the metal remains the same over this temperature range. 2. A Frenkel defect is composed with which of the following? A. A cation interstitial and a cation vacancy B. A cation interstitial and an anion interstitial C. A cation vacancy and an anion vacancy D. An anion interstitial and an anion vacancy 3. For an alloy that consists of 37.7 wt% Pb and 62.3 wt% Sn, what is the composition (a) of Pb (in at%), and (b) of Sn (in at%)? The atomic weights for Pb and Sn are 207.2 and 118.7 g/mol, respectively. 4. Impurity atoms in ceramic materials may form substitutional and interstitial solid solutions. A. True B. False 5. What are the two fundamental types of dislocations? 6. Two metal specimens, A and B, have ASTM grain size numbers of 3 and 8, respectively. Which specimen has the larger grain size? A. B. 7. Describe both vacancy and self-interstitial crystalline defects. 8. Define stoichiometric, and cite one example of a nonstoichiometric material. 9. It is possible to produce a perfect crystalline solid that does not contain any vacancies. A. True B. False 10. The surface energy of a single crystal depends on the crystallographic orientation with respect to the surface. A. True B. False 11. Calculate the fraction of atom sites that are vacant for silver at 661°C. Assume an energy for vacancy formation of 0.63 eV/atom. 12. For an alloy that consists of 94.6 g copper, 113 g zinc, and 8.36 g lead, what are the concentrations (a) of Cu (in at%), (b) of Zn (in at%), and (c) of Pb (in at%)? The atomic weights for Cu, Zn, and Pb are 63.55, 65.39, and 207.2 g/mol, respectively.