Metal 259

Exam 3 - Fall 2001

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

a. alpha - limited, gamma - extensive
b. alpha - extensive, gamma - limited
c. alpha - limited, gamma - limited
d. alpha - extensive, gamma - extensive

Data: Atomic radii

Ni = 1.24 Å, Fe = 1.25 Å

Crystal structures

alpha-Fe is "bcc", gamma-Fe is close-packed, Ni is close-packed

2. The choices for a thin spring material to be used for springs to hold a polymer film against a platen (needed in a hurry), as discussed in class, was limited to two alloys mainly based upon:

a. properties
b. availability
c. business issues
d. economics

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. A business issues factor to be considered in the selection of a metallic material (according to class discussions):

a. recyclability
b. mechanical properties
c. manufacturability
d. minimum order requirements
e. weldability

5. A way to suppress corrosion:

a. use a carbon steel filler rod when welding stainless steel
b. in a Fe-Cu cell, replace the anode with Pt
c. cold roll the metal piece
d. make the metal electrically positive
e. galvanize

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

a. recyclability
b. machinability
c. formability
d. heat treatment is required
e. weldability

7. Not characteristic of Ti metal:

a. welds easily, just like low carbon steels
b. expensive
c. allotropic
d. highly reactive with oxygen at elevated temperatures
e. excellent corrosion resistance

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. toughness
b. toxicity
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. a martensitic stainless steel

10. Mandrel:

a. pop singer
b. a drill
c. a heat treatment tool
d. part of a metalworking tool
e. a pipe

11. Use of which of the following alloys should result in the lowest weight for a bicycle frame:

a. Ti-3Al-2.5V
b. 6061-T6
c. chrome-moly steel
d. plain carbon steel

12. Which shows evidence for sensitization?:

a.

b.

c.

d.

e.

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

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 (above) and the cartridge inside the faucet (below) 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. The formation of a HAZ during welding may lead to:

a. corrosion
b. sensitization in stainless steels
c. decrease in strength
d. increase in strength
e. all of the above

21. Titanium and its alloys are not widely used materials because they require an expensive process to make them. However, titanium is still a useful material. What property of titanium overcomes the high cost and makes it an attractive material to use?

a. Ti becomes an oxygen sponge at high temperatures
b. Ti is a readily available natural resource
c. Ti has excellent corrosion resistance
d. when Ti is welded, an inert gas must be used to maintain strength

22. What is/are the most important alloying element(s) for titanium?

a. aluminum
b. manganese
c. vanadium
d. a and b
e. a and c

23. What purpose does chromium serve in chromium plating?

a. to smooth the metal surface
b. to make the metal surface look good
c. to protect the substrate metal from corrosion
d. to prevent crevice formation

24. Which type of welding uses a non-consumable electrode?

a. arc welding
b. MIG welding
c. TIG welding
d. brazing
e. HAZ welding

25. In order to get rid of a galvanic cell you must eliminate which of the following:

I. anode
II. cathode
III. electrolyte
IV. connection
V. carbide precipitates

Choose the best answer:

a. I or II or IV or V
b. IV and V
c. III
d. I, II, III, IV, V
e. I and II

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.

material density modulus

material yield yield/density

Galvanic series:

Au
Ti
Ag
SS (passive)
Inconel
Ni (passive)
Cu
brasses
Ni (active)
Sn
Pb
SS (active)
cast irons
steels
Cd
Al (active)
Zn
Mg