This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Annealing – 7”.
1. Polygonization is essentially completed before the start of ______
d) grain growth
Explanation: Polygonization is essentially completed before the start of recrystallization, the stored energy can be assumed to be confined to the dislocations in polygon walls. The elimination of the sub-boundaries is a basic part of the recrystallization process.
2. The recrystallized grain size is the crystal size immediately at the end of ______
d) 1 hr from the start of the recrystallization
Explanation: The recrystallized grain size is the crystal size immediately at the end of recrystallization, that is before grain growth proper has had a chance to occur. The recrystallized grain size depends upon the amount of deformation given to the specimens before annealing.
3. The grain size grows rapidly with decreasing ______
c) yield strength
Explanation: The grain size grows rapidly with decreasing deformation. Too little deformation, however, will make recrystallization impossible in any reasonable length of time.
4. The critical amount of cold work is the ______
a) minimum amount of cold work that allows recrystallization
b) maximum amount of cold work that allows recrystallization
c) amount of cold work need to recover the specimen
d) amount of cold work needed to increase the yield strength by 10 MPa
Explanation: For very small deformation there will be no recrystallization in the specimen. This leads to the concept of the critical amount of cold work, which may be defined as the minimum amount of cold deformation that allows the specimen to recrystallize (within a reasonable time period).
5. The critical deformation is not dependent on ______
a) material properties
Explanation: The critical deformation is not a property of the metal since its value varies with the type of deformation; for example — tension, torsion, compression, rolling, bending, etc.
6. Plastic deformation occurs without roughing of the surface if the grain size of the metal is less than _____ in diameter.
a) 0.002 mm
b) 0.05 mm
c) 0.1 mm
d) 1 mm
Explanation: If the grain size of metal is very small (less than ~0.05 mm in diameter), plastic deformation occurs without appreciable roughing of the surface (assuming that deformation does not occur by movement of Lüdersbands).
7. If the diameter of the average grain is large, cold working produces _____
a) smooth surface
b) roughened surface
c) highly tensed surface
Explanation: If the diameter of the average grain is large, cold working produces a roughened, objectionable surface. Such a phenomenon is frequently identified by the term orange peel effect because of the similarity of the roughened surface to that of the peel of a common orange.
8. Which of the following is responsible for the orange-peel effect?
a) Large diameter
b) Isotropic nature of the material
c) Anisotropic nature of the material
Explanation: The anisotropic nature of plastic strain inside crystals is directly responsible for the orange-peel effect, and the larger the crystals the more evident will be the nonhomogeneous nature of the deformation.
9. Critical deformation may exceed several hundred percent in case of deformation due to easy glide.
Explanation: In single crystals of hexagonal metals, when deformation occurs by an easy glide, the critical deformation may exceed several hundred percent. Twisting the same crystal to a few percent strain, however, may make it possible to recrystallize the specimen.
10. In metal that is cold-rolled, it is relatively easy to avoid a critical amount of cold work.
Explanation: In metal that is cold-rolled (sheet) or drawn cold through dies (wires, rods, and pipe), it is relatively easy to avoid a critical amount of cold work because the metal is more or less uniformly deformed.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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