Jeff Lyster T. Ferrera
Assignment 5
1. Cite three reasons why ferrous alloys are used so extensively. Cite three characteristics of
ferrous alloys that limit their utilization.
(a) Ferrous alloys are used extensively because Iron ores exist in abundant quantities.
Economical extraction, refining, and fabrication techniques are available. The alloys may be
tailored to have a wide range of properties.
(b) Disadvantages of ferrous alloys are: They are susceptible to corrosion ü They have a
relatively high density ü They have relatively low electrical conductivities
2. Cite five important characteristics for polymers that are to be used in thin-film
applications.
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Low density.
A high degree of flexibility.
High tensile & tear strengths.
Resistance to moisture.
Low permeability to gases.
3. List four situations in which casting is the preferred fabrication technique.
1) For large pieces and/or complicated shapes. (2) When mechanical strength is not an important
consideration. (3) For alloys having low ductility. (4) When it is the most economical fabrication
technique.
4. Name three factors that influence the degree to which vitrification occurs in clay based
ceramic wares. Explain how density, firing distortion, strength, corrosion resistance, and
thermal conductivity are affected by the extent of vitrification.
(a) Factors affecting the degree to which vitrification occurs:
- The firing temperature: The maximum temperature that can be obtained.
- The time when the body reaches firing temperature.
- The concentration of components.
(b)
- As the extent of vitrification increases, the density increases due to an increase in the size of
pores.
- Firing distortion will increase with the increase in the extent of vitrification due to the presence
of more components in the liquid phase at maximum(firing) temperature.
- The higher extent of vitrification also causes an increase in strength due to the higher volume
fraction of pores.
- Due to less surface area being exposed to a corrosive medium, the corrosive resistance
increases with an increase in the extent of vitrification.
- Since the glass matrix formed will have higher conductivity, the thermal conductivity increases
with the increase in the degree of vitrification.
5. Cite four factors that determine what fabrication technique is used to form polymeric
materials.
(1) whether the polymer is thermoplastic or thermosetting; (2) if thermoplastic, the softening
temperature; (3) atmospheric stability; and (4) the geometry and size of the finished product.