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Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.
Reason (R): Grain boundaries provide easy paths to dislocation motion.
Reason (R): Grain boundaries provide easy paths to dislocation motion.
- a)Both A and R are individually true and R is the correct explanation of A
- b)Both A and R are individually true but R is not the correct explanation of A
- c)A is true but R is false
- d)A is false but R is true
Correct answer is option 'C'. Can you explain this answer?
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Assertion (A): Refining the grain size of a polycrystalline material r...
Ans. (c)
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Assertion (A): Refining the grain size of a polycrystalline material r...
Assertion (A): Refining the grain size of a polycrystalline material renders it harder and stronger.
Reason (R): Grain boundaries provide easy paths to dislocation motion.
Explanation:
Grain boundaries are the interfaces between two adjacent grains in a polycrystalline material. Refining the grain size of a polycrystalline material means reducing the size of the grains, and hence increasing the number of grain boundaries present. The assertion is true because of the following reasons:
- When the grain size is refined, the number of grain boundaries increases. This leads to increased resistance to dislocation motion. Dislocations are the defects in the crystal lattice that allow plastic deformation to occur. When a dislocation encounters a grain boundary, it gets pinned and cannot move easily. This increases the strength of the material.
- Refining the grain size also leads to a reduction in the size of the individual grains. This leads to a reduction in the size of the regions where slip occurs. As a result, the deformation of the material becomes more uniform, and the strength of the material increases.
The reason provided in the assertion is correct. However, the reason provided in the reason is not completely correct. Grain boundaries do provide easy paths to dislocation motion, but they also act as barriers to dislocation motion. This is because dislocations get pinned at grain boundaries and cannot move easily. Therefore, the reason provided in the reason is partly correct, but not the complete explanation.
Hence, option (C) is the correct answer.
Reason (R): Grain boundaries provide easy paths to dislocation motion.
Explanation:
Grain boundaries are the interfaces between two adjacent grains in a polycrystalline material. Refining the grain size of a polycrystalline material means reducing the size of the grains, and hence increasing the number of grain boundaries present. The assertion is true because of the following reasons:
- When the grain size is refined, the number of grain boundaries increases. This leads to increased resistance to dislocation motion. Dislocations are the defects in the crystal lattice that allow plastic deformation to occur. When a dislocation encounters a grain boundary, it gets pinned and cannot move easily. This increases the strength of the material.
- Refining the grain size also leads to a reduction in the size of the individual grains. This leads to a reduction in the size of the regions where slip occurs. As a result, the deformation of the material becomes more uniform, and the strength of the material increases.
The reason provided in the assertion is correct. However, the reason provided in the reason is not completely correct. Grain boundaries do provide easy paths to dislocation motion, but they also act as barriers to dislocation motion. This is because dislocations get pinned at grain boundaries and cannot move easily. Therefore, the reason provided in the reason is partly correct, but not the complete explanation.
Hence, option (C) is the correct answer.
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Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.Reason (R): Grain boundaries provide easy paths to dislocation motion.a)Both A and R are individually true and R is the correct explanation of Ab)Both A and R are individually true but R is not the correct explanation of Ac)A is true but R is falsed)A is false but R is trueCorrect answer is option 'C'. Can you explain this answer?
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Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.Reason (R): Grain boundaries provide easy paths to dislocation motion.a)Both A and R are individually true and R is the correct explanation of Ab)Both A and R are individually true but R is not the correct explanation of Ac)A is true but R is falsed)A is false but R is trueCorrect answer is option 'C'. Can you explain this answer? for Mechanical Engineering 2024 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.Reason (R): Grain boundaries provide easy paths to dislocation motion.a)Both A and R are individually true and R is the correct explanation of Ab)Both A and R are individually true but R is not the correct explanation of Ac)A is true but R is falsed)A is false but R is trueCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.Reason (R): Grain boundaries provide easy paths to dislocation motion.a)Both A and R are individually true and R is the correct explanation of Ab)Both A and R are individually true but R is not the correct explanation of Ac)A is true but R is falsed)A is false but R is trueCorrect answer is option 'C'. Can you explain this answer?.
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ample number of questions to practice Assertion (A): Refining the grain size of a polycrystalline material renders itharder and stronger.Reason (R): Grain boundaries provide easy paths to dislocation motion.a)Both A and R are individually true and R is the correct explanation of Ab)Both A and R are individually true but R is not the correct explanation of Ac)A is true but R is falsed)A is false but R is trueCorrect answer is option 'C'. Can you explain this answer? tests, examples and also practice Mechanical Engineering tests.
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