Multiple Choice 6. On the basis of microstructure, briefly explain why gray iron
ID: 977603 • Letter: M
Question
Multiple Choice
6. On the basis of microstructure, briefly explain why gray iron is brittle and weak in tension.
a. The graphite phase is brittle which makes the entire material brittle
b. The flake shape of the graphite introduces stress concentration locations which cause the material to become brittle
c. The iron-rich phase can form pearlite under some situations which creates a brittle material
d. The grain size of the material is small which translates to poor ductility
7. Which casting method uses a wax pattern?
a. Sand casting
b. Die casting
c. Investment casting
d. Continuous casting
8. What is the difference between hot working and cold working?
a. Hot working is done at temps above the recrystallization temperature, clod working is below the recrystallization temperature
b. Hot working is done at temps higher than 100 °C (boiling point of water), cold work is done at temps at or below 100 °C
c. Hot working uses a flame to heat the material during processing, cold working uses a stream of cold water sprayed on the material during processing
d. Hot working is done above the solidus temperature of the alloy, cold work is done below the solidus
Explanation / Answer
Multiple Choice
6. On the basis of microstructure, briefly explain why gray iron is brittle and weak in tension.
a. The graphite phase is brittle which makes the entire material brittle
b. The flake shape of the graphite introduces stress concentration locations which cause the material to become brittle
c. The iron-rich phase can form pearlite under some situations which creates a brittle material
d. The grain size of the material is small which translates to poor ductility
Gray iron is weak and brittle in tension because the flake shape of the graphite introduces stress concentration locations which cause the material to become brittle
7. Which casting method uses a wax pattern?
a. Sand casting
b. Die casting
c. Investment casting
d. Continuous casting
Investment casting method uses a wax pattern. In this method combination of paraffin wax, bees wax and carnauba wax is used for casting.
8. What is the difference between hot working and cold working?
a. Hot working is done at temps above the recrystallization temperature, clod working is below the recrystallization temperature
b. Hot working is done at temps higher than 100 °C (boiling point of water), cold work is done at temps at or below 100 °C
c. Hot working uses a flame to heat the material during processing, cold working uses a stream of cold water sprayed on the material during processing
d. Hot working is done above the solidus temperature of the alloy, cold work is done below the solidus
the correct answer is a.
Hot working is done at temps above the recrystallization temperature, clod working is below the recrystallization temperature
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