JNTU
JNTU B.Tech II METALLURGY AND MATERIAL SCIENCE Previous Question Paper (March - 2021 - R16)
Answer any five questions. All questions carry equal marks.
Main
Distinguish between grains and grain boundaries.
Answer
Grains are individual, small, crystalline regions within a polycrystalline material where the atoms are arranged in a periodic, ordered lattice structure. They represent the bulk volume of the solid.
Grain boundaries are the narrow, disordered interfacial regions that separate adjacent grains of different crystallographic orientations. These regions contain atoms that are not in perfect lattice positions, leading to higher energy and increased chemical reactivity compared to the grain interiors.
How the packing efficiency of a crystal structure is defined.
Answer
Packing efficiency, or Atomic Packing Factor (APF), is defined as the ratio of the volume of atoms in a unit cell to the total volume of the unit cell. It is a measure of how efficiently atoms are packed within the crystal lattice, assuming atoms are hard spheres.
Show that the atomic packing factor of FCC crystal structure is 74%.
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Explain the Gibb’s Phase rule.
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Define allotropy. Give atleast three examples.
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What information can be obtained from an equilibrium diagram?
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Discuss any three methods of construction of phase diagrams. Explain the limitations of each method.
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What are the effects of non-equilibrium cooling?
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Explain how the TTT diagrams are constructed and discuss how the phase transformation takes place at different cooling rates when 0.4%C steel is cooled from austenitic phase to room temperature.
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Discuss how martensitic transformation occurs and explain its characteristics.
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Draw Fe – Fe3C phase diagram and indicate all points, lines and areas along with phase transformation reactions.
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Explain the classification of copper and its alloys.
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Discuss the composition, microstructure, properties and applications of grey cast iron.
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Discuss the classification and applications of Polymers.
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What are crystalline ceramics? Give atleast three examples.
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Distinguish between glasses and cermets.
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