MECH 473 Ferrous and Non-Ferrous Materials
Student Name ………………………… Student Number …………………
Assignment #2
Marks shown in brackets ( ) at the end of each question. Total marks are ~69.
Due Friday March 30, 2012
1. What are the principle means of strengthening Copper and its alloys and give an example of a material using these means? (5)
2. When copper and its alloys strengthen by cold working how are the crystal and its dislocation process(es) involved in the strengthening? (2)
Describe the dislocation mechanism involved in cold working Cu and its alloys.
3. What copper alloy is used for thermocouples and why? (1)
4. What Copper alloy is able to make stiff wires and springs? What are the current and a modern application of it at a very small scale? (1)
5. What are two Cu-based shaped memory alloys and how do they work? (1)
6. What is coring and why does it occur in Cu-Ni alloys? (1)
7. What is the most widely used cast Cu alloy and why? (1)
8. Describe the three steps that would be required to age harden the Cu-2%Be alloys. (3)
9. What four conditions must be meet to age harden the Cu-2%Be alloys? (2)
10. Other than Cu alloys, what other alloys are age hardenable? (1)
11. What alloying addition to Al has very low solubility and how is it used by the electronics industry. (1)
12. Why must Mg be added to Al-Si alloys to make them age hardenable? What can be added to Al-Mg alloys to make them age hardenable? (1)
13. What is added to Al-Si alloys and how are they heat treated to enhance their strength and toughness. (1)
14. What is the strengthening phase in Al-Cu alloys? Why is it so effective in strengthening these alloys? On what close-packed atomic planes does this phase block the motion of dislocations? Why do the strength of these alloys fall off if they are aged too long? (2)
15. Why do Al alloys initially soften during aging and why does prior stretching of an Al alloy enhance its aging response? (1)
16. What Al alloy is known for superplasticity and why? What can be added to enhance its precipitation hardening (1)
17. Why is pure Al used to clad Al alloys? Why is it used to clad steel cables used by the power industry? (1)
18. If an Al alloy corrodes (other than forming its protective oxide), what is/are the dislocation mechanism(s) by which it corrodes? (1)
Describe the dislocation mechanism involved in corroding Al and its alloys.
19. What is the structure of the corrosion product on the surface of the Al material and why? (1)
20. Explain why aluminum alloys containing more than about 17% Mg are not used. Assume that the b phase is an intermetallic compound and a eutectic structure is produced. (1)
21. What is a common problem of cast aluminum alloys occurring during solidification and what are two methods by which it can be reduced. (1)
22. The company that you are working for welds aluminum parts together using the GMAW (MIG) process. Currently, they are using CO2 gas to protect the aluminum during the welding process. However, the CO2 gas is too cold and leaves a rough finish on the welds. What gas would you choose to improve the finish on the welds? Why would you choose this particular gas? (1)
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23. Stainless steels can suffer from “weld decay”. What is it? (1)
24. What are three methods that can be used to eliminate weld decay and why? (1)
25. Submerged-arc welding is used for the high-output welding of large steel panels (such as ship decks) in the flat position. Describe the Submerged-Arc Welding process. (1)
26. How should the welding rod match the base steel metal that is heat treatable and non-heat treatable in terms of Ni, Mn, Cr and Mo? (1)
27. Draw the microstructure of steel in the fusion zone and heat-affected zone in a weld showing in a) the initial structure at the maximum temperature, b) the structure after cooling of a low-carbon steel and c) the structure after cooling of a high hardenability steel. (3)
28. By what means does the FIB weld materials at the nanoscale? (1)
FIB = Focused Ion Beam
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29. What is the crystal structure of Mg? What are its close-packed planes and directions? (1)
30. Mg being a highly reactive metal, how is it protected for open and closed crucibles during melting? (1)
31. At what temperatures are Mg alloys solution treated and what happens if the temperature is too high? (1)
32. On a stiffness basis, how does Mg match up with Al and steel? On a mass basis, how does it match? (1)
33. By what means can Mg alloys be welded and what’s possible for temporary repairs in the field? (1)
34. In Mg-Zn alloys show how much alpha phase exists in the eutectic assuming the maximum solubility of Al in the delta phase is 73%. Is the eutectic alloy ductile? (1)
35. What are the two means to strengthen Mg-Al alloys and at which compositions do they apply? (1)
36. At what temperatures can wrought Mg alloys be forged into shapes? By what means and temperature are they strengthened and why? (1)
37. In sand cast Mg alloys, what problems can arise due to the reactive nature of Mg and how is it mitigated in a similar way as in Al alloys? (1)
38. Why are die cast Mg alloys significantly stronger than sand cast alloys and give three uses for them? (1)
39. What are the low-temperature and high-temperature phases of Titanium and how can the high temperature phase be partially and fully stabilized to low temperatures? (2)
40. What are the two mechanisms of deformation in Ti and what are the slip plane and directions active in the hcp material? (2)
41. What impurities easily dissolve in Ti and how are they expressed? (2)
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42. What alloying addition to the a+b Ti alloys is added for high temperature creep resistance and why is it effective? (2)
43. What similar alloys to the Ti alloys are used in the nuclear industry and why? (2)
44. Why is Ta a special material and what new method of processing enables it to be used commercial purposes. Give an example of an application. (2)
45. What is the structure of Nb over its entire temperature range and give two methods of how it is strengthened for high-temperatures applications? (2)
46. What methods (there are 2) and alloying additions are used to enhance the high-temperature strength of Mo and its alloys and to what temperature are they effective? (2)
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47. What is the basis for Tungsten (W) being used for filaments for incandescent light bulbs, as cathodes in electronic and X-ray tubes and as electrodes for welding and other arc sources? What is unique about W that makes it different than the other refractory metals? (2)
48. What crystal orientation of W penetrated a steel target the best and why? (2)
49. Would you expect W to work harden during its extrusion from the tip of the penetrator to its sides? Justify your answer by showing the dislocation mechanism(s) responsible for deformation. (2)
50. How many cracks would it take to make a single crystallite in the W penetrator? What would be the crystal planes operative to make the crystallites? (2)
51. Why are Zirconium Alloys used in nuclear reactors? What are the three Zirconium alloys being used today for the CANDU nuclear reactor? (2)
52. When a thermal neutron collides with a Zr atom what two types of energy dissipation mechanisms occur? What two types of point defects are created? (2)
53. What types of dislocations do the point defects create? How do these defects go on to created an extended dislocation network? (2)
54. What type of material deformation limiting the life-time of the CANDU reactor is created by the annihilation of point defects at the extended dislocation networks? When single crystals of Zr are tested for their deformation, what is the direction dependency of the deformation? (2)
55. What is the term used for the high-rate of material deformation at the high neutron doses and by what two mechanisms are responsible for it? (2)
56. In general, what happens to Fe, Ni and Cr precipitates and grain boundaries during neutron irradiation of Zr alloys? (2)