JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II PHYSICAL METALLURGY Previous Question Paper (April/May - 2023 - R18)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Why alloying is necessary? Explain with examples.
Answer
Alloying is necessary to enhance the mechanical, chemical, or physical properties of a pure metal that are otherwise insufficient for engineering applications. By adding other elements, we can improve strength, corrosion resistance, or wear resistance. For example, adding chromium to iron produces stainless steel, which provides excellent corrosion resistance, while adding carbon to iron creates steel, significantly increasing its hardness and tensile strength.
What is work hardening?
Answer
Work hardening, or strain hardening, is the process by which a ductile metal becomes harder and stronger as it is plastically deformed at temperatures below its recrystallization temperature. This occurs due to the increase in dislocation density within the crystal lattice, where the interaction of dislocations hinders their movement, thereby requiring higher stress for further deformation.
What are CCT curves?
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What is the effect of sulphur in steels?
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What is hardenability?
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What is full annealing? Where it is applied?
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What is over ageing?
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What is yellow brass? Explain its uses.
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List the applications of Ti alloys.
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Explain the applications and properties of pure copper.
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Part B
Draw the Fe – Fe3C equilibrium diagram and label all the points, lines and areas.
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Explain the cooling behavior of 0.4%C steel from liquid state to room temperature giving the quantities of the phases before and after the phase transformation temperatures.
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Explain the principle of precipitation strengthening with examples.
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Differentiate between dispersion hardening and precipitation strengthening.
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Explain the effect of increasing cooling rate on the following: i) Temperature of austenite transformation ii) Fineness of pearlite iii) Amount of proeutectoid constituents.
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Normalised steels show an increase in tensile strength upto 1.2%C and then a decrease. Explain with reasons.
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What is secondary hardening? Explain. Which type of steels exhibit secondary hardening? Why?
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Describe the merits and demerits of the following hardening processes: i) Direct quenching ii) Interrupted quenching.
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Explain the mechanism of formation of BCT martensite from FCC austenite.
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Explain the effect of carbon on the MS and Mf temperatures and on the morphology of martensite in plain carbon steels.
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Discuss in detail the following stainless steels:
a) Ferritic stainless steels
b) Austenitic stainless steels
c) Martensitic stainless steels.
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How are cast irons classified on the basis of their manufacture, composition, microstructure and appearance of fracture? Explain them.
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What is mottled cast iron? How is it manufactured? Explain its properties and applications.
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What are the advantages of spheroidal graphite cast iron over malleable cast iron?
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What are shape memory alloys? Discuss about composition, heat treatment and characteristics of different shape memory alloys.
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How Cu-Zn alloys are classified? Explain at least two examples for each classification stating their composition, microstructure, important characteristics and applications.
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