JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II METALLURGY AND MATERIALS ENGINEERING Previous Question Paper (November/December - 2017 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Distinguish between black heart malleable cast iron and white heart malleable cast iron.
Answer
Black heart malleable iron is produced by annealing white iron in a neutral atmosphere, resulting in a ferritic matrix with temper carbon nodules. White heart malleable iron is produced by annealing white iron in an oxidizing atmosphere (packed in iron ore), which removes carbon from the surface, resulting in a decarburized surface layer and a core that may contain pearlite.
Why is it easier to control the properties of cast irons as compared to steels? Explain covering all points with respect to the above.
Answer
Cast irons have higher carbon (2-4%) and silicon content compared to steels, which lowers their melting point and increases fluidity, allowing for complex casting shapes. Because they solidify closer to the eutectic point, they exhibit less shrinkage and are less sensitive to cooling rate variations than steels, making their microstructural properties (like graphite morphology) easier to manipulate through composition control and inoculation.
What information is obtained from an equilibrium diagram?
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Distinguish between hardness and hardenability.
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“The ratio of ferrite to cementite in pearlite is constant.” Explain.
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Why age hardening process is two step process?
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What is doping? Give an example.
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Define the terms: Diffusion coefficient and Sintering.
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What is condensation polymerization? Explain with example.
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What is degree of polymerization? Explain its significance.
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Part B
Briefly explain about the following:
- Carbide forming elements.
- Austenite stabilizers.
- Ferrite stabilizers.
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Explain the microstructure and properties of plain carbon steels.
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How plain carbon steels are classified? Explain.
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Draw Fe-Fe3C phase diagram and explain the phase transformation reactions in the diagram.
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Explain the relationship between equilibrium diagrams and properties of alloys.
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Discuss about congruent melting phases.
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Discuss about different types of annealing processes.
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Why heat treatment of steels is done? Explain with examples.
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Explain the property and structural changes during cold working and annealing of metals.
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What is critical degree of cold work? Explain.
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Write a short note on the following:
- Widemann – Franz law.
- Intrinsic semiconductors.
- Extrinsic semiconductors.
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Explain the basic requirement for electrical conduction with respect to Fermi energy level in a solid?
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Explain the following: (i) Drift velocity (ii) Mobility of free electrons.
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Explain the factors affecting the properties of a polymer.
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Explain the addition and condensation reactions of polymerization with suitable examples.
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Differentiate between thermoplastic polymers and thermosetting polymers. Give minimum two examples of each type.
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What is vulcanization of rubber? Why it is done?
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