Page 248 - Materials Chemistry, Second Edition

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References
30
For instance, see: Bogdanovi, B.; Schwickardi, M. J. Alloys Compounds 1997, 253-254,1.
31
For example, see: Maiti, A.; Gee, R. H.; Maxwell, R.; Saab, A. P. Chem. Phys. Lett. 2007, 440, 244.
32
For instance, see: Schimmel, H. G.; Huot, J.; Chapon, L. C.; Tichelaar, F. D.; Mulder, F. M. J. Am.
Chem. Soc. 2005, 127, 14348.
33
Note: each Boeing 747 contains ca. 1,500 of depleted uranium for this application.
34
For more details regarding the factors that govern the penetration of targets by metallic projectiles, see:
Doig, A. Military Metallurgy, IOM Communications: London, 1998.
Topics for Further Discussion
1. For iron allotropes, why is the solubility of carbon greater in the austenite phase, relative to the ferrite
phase?
2. Although iron is most stable in its bcc form, why are heavier Group 8 congeners Ru and Os most
stable as hcp?
3. What is the difference between substitutional and interstitial dopants? Provide examples for each type.
4. Calculate the number of vacancies per cubic meter in gold at 900 C. The energy for vacancy

3
formation is 0.98 eV/atom. The density of gold at this temperature is 18.63 g/cm .
5. What is the composition, in weight percent, of an alloy that consists of 5 at.% Cu and 95 at.% Pt?
6. For each of the following metals, provide a description of the extractive metallurgy used to isolate the
metal from specific ores (describe the minerals present in the ore), and post-treatment methods used to
purify the metal: (a) Mo, (b) Rh, (c) Sn, (d) W.
7. For iron allotropes, provide a rationale for: (a) Why iron converts between BCC (a) & FCC (g)
lattices at 910 C, and back to BCC (d) at 1,403 C; (b) Why a-Fe loses its ferromagnetism at 769 C

(both magnetic (a-Fe) and nonmagnetic (b-Fe) allotropes are BCC, with identical lattice parameters
and densities!).
8. Briefly compare and contrast the following metallurgical processing techniques: forging, casting,
drawing, and extrusion.
9. Explain the atomic diffusion processes that occur when steel is heated and subsequently quenched by
cold water. Use diagrams to illustrate your rationale.
10. Name the three types of hydrogen-storage metals/alloys and describe the placement of hydrogen
within each lattice.
11. Consider the sintering process of compacted metal powders. Would the resulting sintered material be
more or less desirable (from a mechanical standpoint), if an excessive amount of metal oxides were
present in the presintered matrix? How would you design the sintering conditions (co-reactant gases,
temperature, etc.) for these matrices?
12. How does precipitation hardening work to strengthen the material?
13. For surface phosphating of aluminum-containing metals, fluoride-based additives are needed to cause
crystallization. Why?
14. Using redox potentials, explain the frequent occurrence of perforations in domestic hot tap water
pipes manufactured from galvanized steel.
15. Explain how shape-memory metals are able to manipulate their shapes in response to temperature
fluctuations. Are there other alloy candidates for this type of behavior?
16. Classify the various phases in the Fe–C system as type I or II alloys (or both).
17. For the density of states for transition metals (e.g., Figure 3.30), the d-band is much narrower than the
overlapping s/p band. Why is this so, and what physical properties does this govern?
18. Explain why many ferrimagnetic materials crystallize in a spinel lattice.
19. Why are finely divided metals pyrophoric?
20. You have been awarded $2.3 million dollars to yield ultrahigh purity germanium from an ore that
contains high concentrations of GeS 2 , as well as Zn and Pb silicates. Outline a strategy that you will
use to accomplish this goal.
21. Compare and contrast martempering and austempering of steel. What products do you obtain
following these treatments?
22. Using the TTT diagram below for an iron-carbon alloy of eutectoid composition, specify the nature of
the final microstructure (in terms of microconstituents present and approximate percentages) of a