259 ex 3 F00

Metal 259

Exam 3 - Fall 2000

Only one answer per question. For a few questions, you may feel that more than one answer works; choose only the best answer.

Code your SS# on your answer sheet now.

1. The Hume-Rothery rules predict for the solubility of alpha-Fe and gamma-Fe in Cr:

a. alpha - limited, gamma - extensive

b. alpha - extensive, gamma - limited

c. alpha - limited, gamma - limited

d. alpha - extensive, gamma - extensive

Data: Atomic radii

Cr- 1.24 Å, Fe - 1.25 Å

Crystal structures

alpha-Fe - "bcc", gamma-Fe - close-packed, Cr - "bcc"

2. The choice for the springs used to hold a polymer film against a platen (needed in a hurry), as discussed in class, was limited to two materials mainly based upon:

a. properties

b. business issues

c. economics

d. availability

3. Not a description of a type of corrosion cell:

a. electrolyte concentration

b. dissimilar metals

c. non-homogeneous stress distribution

d. active-passive regions

e. none of the above

4. Not a business issues factor to be considered in the selection of a metallic material (according to class discussions):

a. recyclability

b. health hazards

c. manufacturability

d. product liability

e. waste disposal

5. Not a way to suppress corrosion:

a. use a carbon steel filler rod when welding stainless steel

b. paint the metal

c. anneal the metal piece

d. make the metal electrically negative

e. use a steel containing a considerable amount of chromium

6. Not an economic factor to be considered in the selection of a metallic material:

a. weldability

b. machinability

c. formability

d. heat treatment is required

e. electrical conductivity

7. A superstrong electromagnet can be made of a coil of Nb3Sn (niobium 3 tin) wire because:

a. the electrical resistance of Nb3Sn goes to zero below a certain critical temperature

b. Nb3Sn has very high corrosion resistance

c. Nb3Sn is ferromagnetic (i.e., it acts like a magnet)

d. dislocation motion in Nb3Sn is extremely easy

8. Which of the following would probably not be a criterion for choosing a material for the manufacture of an inexpensive reusable metal lid for a food canning jar:

a. weldability

b. non-toxic

c. corrosion resistance

d. formability

9. Which of the following is probably the best choice for the manufacture of the jar lid in problem 8:

a. a beryllium alloy

b. Ti-6-4

c. 1020 steel

d. 304 stainless steel

10. Which of the following is probably the best choice for the manufacture of a very high end (i.e., cost doesn't matter to consumer) set of tableware:

a. a beryllium alloy

b. Ti-6-4

c. 1020 steel

d. 304 stainless steel

e. a zinc alloy

11. Use of which of the following alloys would probably result in the highest cost to the consumer for a bicycle frame:

a. Ti-3Al-2.5V

b. 6061-T6

c. chrome-moly steel

d. plain carbon steel

12. Which shows sensitization?:

13. The microcell mainly responsible for corrosion in sensitized stainless steels consists of these anode/cathode combinations:

a. Fe metal/Cr metal

b. low Cr content solid solution/high Cr content solid solution

c. Fe-Cr solid solution/Cr7C3

d. grain boundary/central portion of grain

e. high Cr content solid solution/low Cr content solid solution

14. Not an example of a corrosion microcell:

a. a deeply scratched galvanized coating on steel

b. bulk of a grain/grain boundary region

c. solid solution matrix/precipitate particles

d. segregation

e. grain A/neighboring grain B

15. The pictures below show a sink faucet (left) and the cartridge in the faucet (right) which controls flow rate and water temperature when the faucet handle position is changed. Which of the following materials would be an unlikely candidate for the cartridge material?

a. 303 stainless steel (a machinable grade)

b. acetal copolymer

c. Ti-6-4

d. cartridge brass

16. In problem 15, what property does not need to be considered when choosing a material for the cartridge:

a. weldability

b. corrosion resistance

c. machinability

d. wear resistance

17. In problem 15, suppose the choice of the cartridge material is between 303 and 304 stainless steels. What really determines which material will be chosen?:

a. corrosion resistance

b. susceptibility to sensitization

c. cost of producing the part

d. environmental costs - disposal of worn cartridges

18. In problem 15, what is the best choice from the following list for the cartridge material for a fairly high end faucet:

a. 303 stainless

b. cartridge brass

c. 6061-T6

d. acetal copolymer

e. 9310

19. The major difficulty in marketing stainless steel rod coated with a copper lubricant:

a. the difficulty of applying the copper coating

b. copper is toxic

c. the copper must be removed after final processing

d. copper is not a good lubricant for cold drawing operations

20. A way to "un-sensitize" a sensitized austenitic stainless steel part

a. cold work it

b. pack carburize it

c. harden and temper it

d. hold it at an appropriately high temperature for an extended period of time

e. plate it with chromium

The following is a collection of some possibly useful information. Nothing needs to be done with it except use it if it seems in any way helpful.

density modulus

Plain carbon steel 7.8 gm/cc 200 GPa

Cr-Mo steel 7.8 200

6061-T6 2.7 70

Ti-3Al-2.5V 4.5 110

yield yield/density

Plain carbon steel 240 MPa 30

Cr-Mo steel 485 62

6061-T6 260 95

Ti-3Al-2.5V 700 156

Galvanic series:

SS (passive)

Inconel

Ni (passive)

brasses

Ni (active)

SS (active)

cast irons

steels

Al (active)