This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Annealing – 5”.
1. How many factors are there to determine isothermal phase transformation in terms of time and temperature?
Explanation: The factors that determine isothermal phase transformation in terms of time and temperature are,
• The nucleation rate
• The growth rate
• The density and distribution of nucleation sites
• The overlap of diffusion fields from adjacent transformation volume
• The impingement of adjacent transformed volumes.
2. The time needed to finish the recrystallization is inversely proportional to _____
a) surface area
d) distribution of grains
Explanation: The higher the temperature, the shorter the time needed to finish the recrystallization. Recrystallization starts after the recover (which accounts for initial energy release) and accounts for the second (larger) energy release.
3. The ______ generally does not remain a constant throughout the recrystallization process.
a) strain energy
b) activation energy
c) threshold energy
d) recrystallization energy
Explanation: Modern recrystallization theory indicates that the activation energy generally does not remain a constant throughout the recrystallization process. In most cases, the activation energy changes continuously during recrystallization as the driving force for recrystallization, the stored energy of cold work, is depleted.
4. Recrystallization temperature is the temperature at which a particular metal _______
a) starts melting
b) starts solidifying
c) starts recrystallizing
d) completely recrystallizes
Explanation: Recrystallization temperature is the temperature at which a particular metal with a particular amount of cold deformation will completely recrystallized in a finite period of time, usually 1 hr.
5. ______ is a means of mechanical deformation used on cylindrical rods.
Explanation: Swaging is a means of mechanical deformation used on cylindrical rods in which the diameter of the rod is reduced uniformly by a mechanical hammer equipped with rotating dies.
6. Recrystallization is promoted by ______
a) increasing temperature
b) increasing cold work
c) decreasing grain size
d) decreasing temperature
Explanation: Recrystallization is promoted by increasing amounts of cold work. When annealed at the same temperature, the metal with the larger amount of cold work recrystallizes much faster than that with the lesser reduction.
7. The recrystallization temperature is lowered by _____
a) increasing the surface area of the component
b) increasing the amount of cold work
c) keeping the metal in cold environment
d) decreasing the amount of cold work
Explanation: The temperature at which the metal recrystallizes completely within an hour is lower for a greater amount of cold work. The amount of cold work is measured in terms of the percentage reduction in the area of the cylindrical cross-section.
8. The recrystallization temperature is ______
a) a time dependent function
b) a material property
c) an independent function
d) dependent on polygonization rate
Explanation: To the practical engineer, the sensitivity of the recrystallization process to small changes in temperature makes it appear as though the metal has a fixed temperature, below which it will not recrystallize, and for this reason, there is a tendency to regard the recrystallization temperature as a property of the metal and to neglect the time factor in recrystallization.
9. The origin of a recrystallized grain is always a pre-existing misoriented region.
Explanation: The origin of a recrystallized grain is always a pre-existing region that is highly misoriented in relation to the material surrounding it. This high degree of misorientation gives the region from which the new grain originates the needed growth mobility.
10. Activation energy for recrystallization is dependent on the amount of deformation.
Explanation: The temperature dependence of recrystallization varies with the amount of cold work, or that the activation energy for recrystallization is a function of the amount of deformation.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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