Multiple Choice Questions on Alloys and Phase Diagrams

Multiple Choice Questions on Alloys and Phase Diagrams

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  Multiple Choice Questions Constitutionof Alloys and Phase Diagrams: 1. An alloy is: A) A pure metal B) A mixture of two or more elements, at least one of which is a metal C) A ceramic material D) A polymer Answer: B Reason: An alloy is formed by combining two or more elements, with at least one being a metal, to improve engineering properties. 2. The principal purpose of alloying is to: A) Reduce density only B) Improve the properties of a metal C) Increase electrical resistance only D) Change the colour of a metal Answer: B Reason: Alloying enhances strength, hardness, corrosion resistance, wear resistance, and other desirable properties. 3. Which of the following is NOT an alloy? A) Steel B) Brass C) Bronze D) Copper Answer: D Reason: Copper is a pure metal, whereas steel, brass, and bronze are alloys. 4. Brass is composed mainly of: A) Copper and Tin B) Copper and Zinc C) Copper and Nickel D) Copper and Aluminium Answer: B Reason: Brass is a copper–zinc alloy known for good corrosion resistance and machinability. 5. Bronze is an alloy of: A) Copper and Zinc B) Copper and Tin C) Iron and Carbon D) Nickel and Copper Answer: B Reason: Bronze primarily consists of copper and tin.
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  6. Steel ismainly an alloy of: A) Iron and Zinc B) Iron and Carbon C) Iron and Tin D) Iron and Aluminium Answer: B Reason: Steel contains iron as the base metal and carbon as the principal alloying element. 7. Stainless steel contains a minimum of about: A) 5% Chromium B) 10.5% Chromium C) 25% Chromium D) 40% Chromium Answer: B Reason: At least 10.5% chromium is required to form the protective passive oxide film. 8. Which alloy is widely used for electrical connectors? A) Brass B) Bronze C) Cast iron D) Pig iron Answer: A Reason: Brass has good electrical conductivity and corrosion resistance. 9. Which property generally increases after alloying? A) Mechanical strength B) Hardness C) Corrosion resistance D) All of the above Answer: D Reason: Alloying improves several mechanical and physical properties. 10. The base metal in brass is: A) Zinc B) Copper C) Tin D) Iron Answer: B Reason: Copper is the major constituent of brass. 11. An alloy formed by replacing host atoms with solute atoms is called: A) Interstitial alloy B) Substitutional alloy C) Ceramic alloy D) Composite alloy Answer: B Reason: Solute atoms replace solvent atoms in substitutional alloys.
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  12. An interstitialalloy is formed when: A) Solute atoms replace solvent atoms B) Small atoms occupy interstitial spaces C) Two liquids are mixed D) Two polymers are mixed Answer: B Reason: Small atoms such as carbon fit into the spaces between metal atoms. 13. Carbon in steel occupies: A) Grain boundaries B) Interstitial sites C) Surface defects D) Twin boundaries Answer: B Reason: Carbon atoms are much smaller than iron atoms and occupy interstitial positions. 14. Which is an example of a substitutional alloy? A) Steel B) Brass C) Cast iron D) High-carbon steel Answer: B Reason: Zinc atoms substitute copper atoms in the lattice. 15. Which is an example of an interstitial alloy? A) Brass B) Bronze C) Steel D) Monel Answer: C Reason: Carbon atoms occupy interstitial spaces in iron. 16. The solvent in brass is: A) Zinc B) Copper C) Tin D) Nickel Answer: B Reason: Copper is present in the largest proportion. 17. The minor element added to an alloy is called: A) Solvent B) Solute C) Matrix D) Grain Answer: B Reason: The alloying element present in a smaller amount is the solute.
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  18. Which typeof alloy usually exhibits better ductility? A) Substitutional alloy B) Interstitial alloy C) Ceramic alloy D) Glass Answer: A Reason: Substitutional alloys generally retain better ductility than interstitial alloys. 19. Carbon increases the ______ of steel. A) Hardness B) Ductility C) Electrical conductivity D) Plasticity Answer: A Reason: Increasing carbon content improves hardness and strength. 20. Which alloy is commonly used for bearings? A) Babbitt metal B) Steel C) Brass D) Cast iron Answer: A Reason: Babbitt metal provides low friction and excellent bearing properties. 21. Chromium improves: A) Corrosion resistance B) Electrical conductivity C) Density D) Melting point only Answer: A Reason: Chromium forms a protective oxide layer. 22. Nickel mainly improves: A) Toughness B) Brittleness C) Density only D) Electrical resistance only Answer: A Reason: Nickel enhances toughness and corrosion resistance. 23. Manganese is added to steel primarily to: A) Remove sulphur effects and improve strength B) Reduce hardness C) Reduce melting point D) Increase porosity Answer: A Reason: Manganese acts as a deoxidizer and combines with sulphur.
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  24. Silicon insteel mainly acts as: A) Deoxidizer B) Lubricant C) Coolant D) Flux Answer: A Reason: Silicon removes oxygen during steelmaking. 25. Molybdenum increases: A) High-temperature strength B) Electrical conductivity C) Colour D) Density only Answer: A Reason: Molybdenum improves creep resistance and high-temperature strength. 26. A homogeneous mixture of two or more elements in the solid state is called: A) Solid solution B) Compound C) Ceramic D) Polymer Answer: A Reason: A solid solution has a single-phase crystal structure. 27. Which type of solid solution is formed in brass? A) Interstitial B) Substitutional C) Compound D) Eutectic Answer: B Reason: Zinc atoms replace copper atoms. 28. Which is NOT a requirement for extensive substitutional solid solubility? A) Similar atomic size B) Same crystal structure C) Similar electronegativity D) Large atomic size difference Answer: D Reason: A large difference in atomic size reduces solubility. 29. The maximum atomic size difference permitted for substitutional solid solutions is approximately: A) 5% B) 10% C) 15% D) 30% Answer: C Reason: According to the Hume–Rothery rules, it should be less than about 15%.
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  30. The Hume–Rotheryrules apply mainly to: A) Solid solutions B) Heat treatment C) Welding D) Casting Answer: A Reason: These rules predict substitutional solid solubility. 31. Microstructure is observed using: A) Optical microscope B) Vernier caliper C) Screw gauge D) Ammeter Answer: A Reason: Microstructures are examined under a metallurgical microscope. 32. Grain boundaries separate: A) Two liquids B) Adjacent crystals C) Two gases D) Two polymers Answer: B Reason: Grain boundaries divide crystals of different orientations. 33. Before etching, the specimen should be: A) Painted B) Mirror polished C) Heated to red hot D) Bent Answer: B Reason: A smooth polished surface is essential for proper metallographic examination. 34. Etching is done to: A) Increase hardness B) Reveal microstructure C) Reduce weight D) Remove alloying elements Answer: B Reason: Etching reveals grains and phase boundaries. 35. Fine grains generally improve: A) Strength B) Toughness C) Hardness D) All of the above Answer: D Reason: Fine-grained structures improve overall mechanical performance.
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  36. Pearlite consistsof: A) Ferrite and Cementite B) Ferrite and Austenite C) Austenite and Martensite D) Cementite and Graphite Answer: A Reason: Pearlite is a lamellar mixture of ferrite and cementite. 37. Ferrite is: A) Soft and ductile B) Hard and brittle C) Liquid D) Ceramic Answer: A Reason: Ferrite has low carbon content and excellent ductility. 38. Cementite is: A) Fe₂C B) Fe₃C C) FeC D) Fe₄C Answer: B Reason: Cementite is iron carbide (Fe₃C). 39. The hardest constituent in steel is: A) Ferrite B) Pearlite C) Cementite D) Austenite Answer: C Reason: Cementite is very hard and brittle. 40. Pearlite has a ______ structure. A) Needle-like B) Lamellar C) Spherical D) Cubic Answer: B Reason: Pearlite consists of alternate layers of ferrite and cementite. 41. A phase is: A) A homogeneous portion of a material B) A crack C) A void D) A defect Answer: A Reason: A phase has uniform composition and properties.
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  42. The horizontalaxis of a binary phase diagram represents: A) Pressure B) Composition C) Density D) Time Answer: B Reason: Composition is plotted on the x-axis. 43. The vertical axis represents: A) Temperature B) Pressure C) Time D) Density Answer: A Reason: Temperature is plotted on the y-axis. 44. The line above which the alloy is completely liquid is called the: A) Solidus B) Solvus C) Liquidus D) Eutectic Answer: C Reason: Above the liquidus line, only the liquid phase exists. 45. The line below which the alloy is completely solid is called the: A) Liquidus B) Solidus C) Solvus D) Tie line Answer: B Reason: Below the solidus line, the alloy is fully solid. 46. The region between the liquidus and solidus lines contains: A) Solid only B) Liquid only C) Liquid + Solid D) Gas Answer: C Reason: This is the two-phase region where liquid and solid coexist. 47. The lever rule is used to determine: A) Grain size B) Phase fractions C) Hardness D) Density Answer: B Reason: The lever rule calculates the relative amounts of each phase in a two-phase region.
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  48. The eutecticreaction is: A) Liquid → α + β B) Solid → Liquid C) α → β D) Liquid → Gas Answer: A Reason: In a eutectic reaction, one liquid transforms into two solid phases simultaneously. 49. The eutectic composition has: A) Highest melting temperature B) Lowest melting temperature C) Highest hardness D) Highest density Answer: B Reason: The eutectic composition melts and solidifies at the lowest temperature in the binary system. 50. Which alloy system is a classical eutectic system? A) Lead–Tin (Pb–Sn) B) Iron–Nickel C) Copper–Nickel D) Iron–Chromium Answer: A Reason: The Pb–Sn system is the classic example of a eutectic alloy used in soldering. 51. The Hume–Rothery rules are mainly applicable to: A) Heat treatment B) Solid solution formation C) Welding D) Casting Answer: B Reason: Hume–Rothery rules predict the formation of substitutional solid solutions. 52. According to Hume–Rothery rules, the atomic size difference between solvent and solute atoms should be less than: A) 5% B) 10% C) 15% D) 25% Answer: C Reason: Atomic size difference should generally be less than 15% for extensive solid solubility. 53. One of the Hume–Rothery rules states that the solvent and solute should have: A) Different crystal structures B) Similar crystal structures C) Different melting points D) Different colours Answer: B Reason: Similar crystal structures favor substitutional solid solution formation.
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  54. Similar ______favors extensive solid solubility. A) Density B) Valency C) Hardness D) Grain size Answer: B Reason: Metals with the same valency dissolve more readily in each other. 55. Which factor is NOT included in the Hume–Rothery rules? A) Atomic size B) Crystal structure C) Valency D) Cooling rate Answer: D Reason: Cooling rate affects microstructure but is not a Hume–Rothery criterion. 56. Gibbs phase rule is expressed as: A) F = C + P + 2 B) F = C – P + 2 C) F = P – C + 2 D) F = C + P – 2 Answer: B Reason: Gibbs phase rule is F = C – P + 2. 57. In Gibbs phase rule, F represents: A) Force B) Freedom (Degrees of Freedom) C) Ferrite D) Fraction Answer: B Reason: F denotes the number of independent variables that can be changed. 58. In Gibbs phase rule, P represents: A) Pressure B) Phase C) Point D) Property Answer: B Reason: P denotes the number of phases present. 59. In Gibbs phase rule, C represents: A) Carbon B) Component C) Composition D) Crystal Answer: B Reason: C represents the number of chemically independent components.
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  60. For abinary alloy system, the number of components is: A) 1 B) 2 C) 3 D) 4 Answer: B Reason: A binary system contains two components. 61. Under constant pressure, the condensed phase rule becomes: A) F = C – P + 1 B) F = C + P + 1 C) F = P – C + 1 D) F = C – P + 2 Answer: A Reason: Pressure is constant, reducing one degree of freedom. 62. At the eutectic point of a binary alloy, the degrees of freedom are: A) 0 B) 1 C) 2 D) 3 Answer: A Reason: It is an invariant point. 63. A binary phase diagram contains: A) One component B) Two components C) Three components D) Four components Answer: B Reason: Binary means two-component system. 64. The horizontal axis of a binary phase diagram represents: A) Temperature B) Composition C) Pressure D) Time Answer: B Reason: Composition is plotted on the x-axis. 65. The vertical axis represents: A) Temperature B) Composition C) Pressure D) Density Answer: A Reason: Temperature is plotted on the y-axis.
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  66. Above theliquidus line, the alloy is: A) Completely solid B) Completely liquid C) Liquid + Solid D) Gas Answer: B Reason: The alloy exists only in the liquid state. 67. Below the solidus line, the alloy is: A) Liquid B) Solid C) Liquid + Solid D) Vapour Answer: B Reason: The alloy is completely solid. 68. Between the liquidus and solidus lines lies the: A) Single solid region B) Single liquid region C) Two-phase region D) Gas region Answer: C Reason: Both solid and liquid coexist. 69. The line separating one solid phase from two solid phases is called: A) Liquidus B) Solidus C) Solvus D) Tie line Answer: C Reason: Solvus separates solid solution regions. 70. A tie line is also known as: A) Isothermal line B) Vertical line C) Cooling line D) Liquid line Answer: A Reason: Tie lines are horizontal lines drawn at constant temperature. 71. The lever rule is used to determine: A) Hardness B) Phase fraction C) Grain size D) Density Answer: B Reason: It calculates the proportion of phases in a two-phase region.
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  72. The leverrule is applicable only in: A) Single-phase region B) Two-phase region C) Gas region D) Liquid region Answer: B Reason: It is valid only when two phases coexist. 73. The lever rule is based on the principle of: A) Mass balance B) Heat transfer C) Newton's law D) Hooke's law Answer: A Reason: The phase fractions satisfy mass conservation. 74. In the lever rule, the phase fraction is proportional to: A) Adjacent arm length B) Opposite arm length C) Temperature D) Pressure Answer: B Reason: Each phase fraction is proportional to the opposite side of the tie line. 75. Which line is essential for applying the lever rule? A) Vertical line B) Tie line C) Liquidus line D) Solidus line Answer: B Reason: The tie line provides the compositions needed for calculation. 76. The eutectic reaction is represented by: A) L → α + β B) α → β C) α + β → L D) L → α Answer: A Reason: One liquid transforms into two solid phases. 77. The eutectoid reaction is: A) Liquid → Two solids B) One solid → Two solids C) Two solids → Liquid D) Solid → Liquid Answer: B Reason: One solid phase transforms into two solid phases.
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  78. The peritecticreaction is represented by: A) L + α → β B) α → β + L C) L → α + β D) β → α Answer: A Reason: Liquid and one solid combine to form another solid. 79. The peritectoid reaction is represented by: A) α + β → γ B) L → α + β C) α → β D) L + α → β Answer: A Reason: Two solid phases react to form a new solid phase. 80. Which reaction occurs completely in the solid state? A) Eutectoid B) Eutectic C) Monotectic D) Peritectic Answer: A Reason: The eutectoid reaction involves only solid phases. 81. A cooling curve represents the variation of: A) Pressure with time B) Temperature with time C) Density with time D) Hardness with time Answer: B Reason: Cooling curves show how temperature changes during cooling. 82. During solidification, the temperature remains constant due to: A) Sensible heat B) Latent heat C) Radiation D) Convection Answer: B Reason: Latent heat of fusion is released. 83. A horizontal portion on a cooling curve indicates: A) Heating B) Phase transformation C) Melting D) Expansion Answer: B Reason: Temperature remains constant during transformation.
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  84. Pure metalssolidify at: A) A range of temperatures B) A constant temperature C) Room temperature D) Variable pressure Answer: B Reason: Pure metals have a fixed melting point. 85. Most alloys solidify over: A) A single temperature B) A temperature range C) Room temperature D) 100°C only Answer: B Reason: Most alloys have a freezing range. 86. Grain boundaries are clearly visible after: A) Painting B) Etching C) Heating D) Forging Answer: B Reason: Etching reveals grain boundaries. 87. Fine grains are produced by: A) Slow cooling B) Rapid cooling C) Long annealing D) Furnace cooling Answer: B Reason: Rapid cooling limits grain growth. 88. Which microstructure has alternate layers of ferrite and cementite? A) Austenite B) Pearlite C) Martensite D) Ferrite Answer: B Reason: Pearlite has a lamellar structure. 89. Ferrite has a ______ crystal structure. A) FCC B) BCC C) HCP D) BCT Answer: B Reason: α-Ferrite has a body-centered cubic structure.
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  90. Austenite hasa ______ crystal structure. A) BCC B) FCC C) HCP D) BCT Answer: B Reason: γ-Austenite possesses a face-centered cubic structure. 91. Which alloy is commonly used for making bearings? A) Babbitt metal B) Brass C) Bronze D) Steel Answer: A Reason: Babbitt metal has excellent anti-friction properties. 92. Which alloy is widely used in coins? A) Brass B) Bronze C) Cupro-nickel D) Cast iron Answer: C Reason: Cupro-nickel offers good wear and corrosion resistance. 93. Which alloy is widely used for soldering electrical joints? A) Steel B) Brass C) Lead–Tin alloy D) Bronze Answer: C Reason: Pb–Sn solder has a low melting point and good wetting characteristics. 94. Stainless steel is preferred because of its: A) High density B) Corrosion resistance C) Low melting point D) High electrical conductivity Answer: B Reason: Chromium forms a passive oxide film that resists corrosion. 95. Brass is commonly used for valves because it has: A) Good machinability and corrosion resistance B) High brittleness C) Very high hardness D) Poor conductivity Answer: A Reason: Brass is easy to machine and resists corrosion.
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  96. Which coolingcondition generally produces the finest grain size? A) Furnace cooling B) Air cooling C) Rapid quenching D) Slow cooling Answer: C Reason: Rapid quenching minimizes grain growth. 97. Which constituent provides maximum hardness in plain carbon steel? A) Ferrite B) Pearlite C) Cementite D) Austenite Answer: C Reason: Cementite (Fe₃C) is the hardest constituent in the iron–carbon system. 98. Which phase diagram line separates the liquid phase from the liquid + solid region? A) Solvus B) Solidus C) Liquidus D) Tie line Answer: C Reason: The liquidus line marks the boundary above which the alloy is completely liquid. 99. Which rule is used to calculate the percentage of phases in a two-phase region? A) Gibbs phase rule B) Hume–Rothery rule C) Lever rule D) Raoult's law Answer: C Reason: The lever rule determines the relative amounts of each phase present in a two- phase region. 100. Which of the following is the most fundamental objective of studying phase diagrams? A) To determine machining speed B) To predict phases and microstructures under equilibrium conditions C) To measure hardness D) To calculate density Answer: B Reason: Phase diagrams are used to predict the phases and resulting microstructures of alloys at different temperatures and compositions under equilibrium conditions. 101. The iron–carbon equilibrium diagram is also called the: A) Copper–zinc diagram B) Iron–cementite diagram C) Lead–tin diagram D) Aluminium–silicon diagram Answer: B Reason: The equilibrium diagram is based on the iron–cementite (Fe–Fe₃C) system.
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  102. The maximumcarbon content shown in the iron–carbon diagram is: A) 2.11% B) 4.3% C) 6.67% D) 8% Answer: C Reason: Cementite (Fe₃C) contains 6.67% carbon. 103. Pure iron melts at approximately: A) 910°C B) 1147°C C) 1394°C D) 1538°C Answer: D Reason: Pure iron melts at about 1538°C. 104. Ferrite is represented by the symbol: A) γ B) α C) δ D) β Answer: B Reason: Ferrite is the α-phase of iron. 105. Austenite is represented by: A) α B) β C) γ D) δ Answer: C Reason: Austenite is the γ-phase of iron. 106. Delta ferrite is represented by: A) α B) β C) γ D) δ Answer: D Reason: Delta ferrite is stable at very high temperatures. 107. Ferrite has which crystal structure? A) FCC B) BCC C) HCP D) BCT Answer: B Reason: Ferrite possesses a Body-Centered Cubic (BCC) structure.
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  108. Austenite haswhich crystal structure? A) BCC B) FCC C) HCP D) BCT Answer: B Reason: Austenite has a Face-Centered Cubic (FCC) structure. 109. Which phase has the highest carbon solubility? A) Ferrite B) Austenite C) Cementite D) Pearlite Answer: B Reason: Austenite dissolves up to about 2.11% carbon. 110. Ferrite can dissolve a maximum of approximately: A) 0.022% carbon B) 0.8% carbon C) 2.11% carbon D) 4.3% carbon Answer: A Reason: Ferrite has very low carbon solubility. 111. The eutectoid temperature is approximately: A) 723°C B) 910°C C) 1147°C D) 1538°C Answer: A Reason: The eutectoid reaction occurs at approximately 723°C. 112. The eutectic temperature in the Fe–C diagram is: A) 723°C B) 910°C C) 1147°C D) 1538°C Answer: C Reason: The eutectic reaction occurs at 1147°C. 113. The eutectoid composition contains: A) 0.022% C B) 0.76% C C) 2.11% C D) 4.3% C Answer: B Reason: The eutectoid composition is about 0.76% carbon.
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  114. The eutecticcomposition is: A) 0.76% B) 2.11% C) 4.3% D) 6.67% Answer: C Reason: The eutectic point occurs at 4.3% carbon. 115. Cementite contains: A) 2.11% carbon B) 4.3% carbon C) 6.67% carbon D) 0.76% carbon Answer: C Reason: Cementite (Fe₃C) contains 6.67% carbon. 116. Pearlite is formed by the eutectoid transformation of: A) Ferrite B) Austenite C) Cementite D) Delta ferrite Answer: B Reason: Austenite transforms into pearlite at the eutectoid temperature. 117. Pearlite consists of: A) Ferrite + Cementite B) Ferrite + Austenite C) Austenite + Cementite D) Martensite + Ferrite Answer: A Reason: Pearlite is a lamellar mixture of ferrite and cementite. 118. Cementite is: A) Soft and ductile B) Hard and brittle C) Liquid D) Magnetic at all temperatures Answer: B Reason: Cementite is extremely hard and brittle. 119. Ferrite is: A) Hard and brittle B) Soft and ductile C) Harder than cementite D) Brittle Answer: B Reason: Ferrite is soft with excellent ductility.
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  120. Austenite isgenerally: A) Non-magnetic B) Ferromagnetic C) Ceramic D) Brittle Answer: A Reason: Austenite is non-magnetic because of its FCC structure. 121. Hypoeutectoid steels contain: A) Less than 0.76% carbon B) Exactly 0.76% carbon C) More than 2.11% carbon D) 4.3% carbon Answer: A Reason: Hypoeutectoid steel has a carbon content below the eutectoid composition of approximately 0.76% C. 122. Hypereutectoid steels contain: A) Less than 0.76% carbon B) Between 0.76% and 2.11% carbon C) Above 4.3% carbon D) Above 6.67% carbon Answer: B Reason: Hypereutectoid steels have carbon content greater than the eutectoid composition (0.76%) but below the steel–cast iron boundary of about 2.11% C. 123. The microstructure of hypoeutectoid steel below 723°C consists of: A) Ferrite + Pearlite B) Pearlite + Cementite C) Ferrite only D) Austenite only Answer: A Reason: On slow cooling below the eutectoid temperature, proeutectoid ferrite forms first, followed by pearlite from the remaining austenite. 124. The microstructure of hypereutectoid steel below 723°C consists of: A) Ferrite + Pearlite B) Pearlite + Cementite C) Austenite + Ferrite D) Cementite only Answer: B Reason: Proeutectoid cementite forms before the eutectoid reaction, and the remaining austenite transforms into pearlite. 125. At the eutectoid composition, the final microstructure is: A) Ferrite only B) Pearlite only C) Cementite only D) Austenite Answer: B
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  Reason: At approximately0.76% carbon, austenite transforms completely into pearlite at the eutectoid temperature. 126. Cast iron contains carbon approximately between: A) 0.02–0.8% B) 0.8–2.11% C) 2.11–6.67% D) Above 7% Answer: C Reason: Cast irons generally contain more than about 2.11% carbon and up to the maximum carbon solubility represented by 6.67% in the Fe–Fe₃C diagram. 127. Steel contains carbon up to: A) 0.76% B) 2.11% C) 4.3% D) 6.67% Answer: B Reason: In the conventional Fe–Fe₃C diagram, alloys containing up to approximately 2.11% carbon are classified as steels. 128. The eutectic reaction in cast iron produces: A) Pearlite B) Ledeburite C) Bainite D) Martensite Answer: B Reason: At approximately 4.3% carbon and 1147°C, liquid transforms into austenite and cementite, forming the eutectic constituent called ledeburite. 129. Ledeburite is formed at: A) 723°C B) 910°C C) 1147°C D) 1538°C Answer: C Reason: The eutectic reaction in the Fe–Fe₃C system occurs at approximately 1147°C. 130. White cast iron contains carbon mainly in the form of: A) Graphite B) Cementite C) Ferrite D) Austenite Answer: B Reason: Rapid cooling and suitable composition promote the formation of cementite rather than free graphite, producing hard and brittle white cast iron.
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  131. Which constituentgives maximum ductility? A) Ferrite B) Cementite C) Pearlite D) Ledeburite Answer: A Reason: Ferrite is a soft, low-carbon solid solution of carbon in α-iron and therefore has high ductility. 132. Which constituent gives maximum hardness? A) Ferrite B) Cementite C) Austenite D) Pearlite Answer: B Reason: Cementite (Fe₃C) is a very hard and brittle intermetallic compound. 133. Which phase is stable above 1394°C in pure iron? A) Ferrite B) Delta ferrite C) Austenite D) Pearlite Answer: B Reason: Pure iron changes from austenite to delta ferrite at approximately 1394°C and remains delta ferrite up to its melting point. 134. Which phase exists between 910°C and 1394°C in pure iron? A) Ferrite B) Delta ferrite C) Austenite D) Cementite Answer: C Reason: Pure iron has austenite (γ-iron) with an FCC structure between approximately 912°C and 1394°C. 135. Which phase exists below 910°C in pure iron? A) Austenite B) Ferrite C) Delta ferrite D) Liquid Answer: B Reason: Below approximately 912°C, pure iron exists as α-ferrite, which has a BCC crystal structure. 136. Why is ferrite softer than cementite? A) Lower carbon content B) Higher density C) More alloying elements D) Higher melting point Answer: A
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  Reason: Ferrite containsonly a very small amount of dissolved carbon, whereas cementite contains about 6.67% carbon and is much harder. 137. Which phase has the highest ductility? A) Ferrite B) Cementite C) Pearlite D) Ledeburite Answer: A Reason: Ferrite is relatively soft and has a BCC structure with very low carbon content, giving it high ductility. 138. Which phase possesses FCC crystal structure? A) Ferrite B) Cementite C) Austenite D) Pearlite Answer: C Reason: Austenite, or γ-iron, has a face-centred cubic (FCC) crystal structure. 139. Which constituent is a mechanical mixture rather than a single phase? A) Ferrite B) Cementite C) Pearlite D) Austenite Answer: C Reason: Pearlite consists of alternating layers of ferrite and cementite. 140. Which microstructure is obtained at the eutectoid composition after slow cooling? A) Ferrite B) Pearlite C) Cementite D) Austenite Answer: B Reason: At the eutectoid composition, all austenite transforms into pearlite during slow cooling through the eutectoid temperature. 141. Increasing carbon content in steel generally increases: A) Ductility B) Hardness C) Weldability D) Toughness Answer: B Reason: Higher carbon content promotes the formation of harder constituents such as pearlite and cementite and increases the potential hardness of steel.
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  142. Increasing carboncontent generally decreases: A) Hardness B) Strength C) Ductility D) Wear resistance Answer: C Reason: Higher carbon content increases the proportion of hard and brittle constituents, reducing the ability of steel to undergo plastic deformation. 143. Which phase can dissolve the maximum amount of carbon? A) Ferrite B) Austenite C) Cementite D) Pearlite Answer: B Reason: Austenite has an FCC structure, which can dissolve significantly more carbon than ferrite. Its maximum carbon solubility in the Fe–Fe₃C diagram is about 2.11% at 1147°C. 144. Cementite is chemically represented as: A) FeC B) Fe₂C C) Fe₃C D) Fe₄C Answer: C Reason: Cementite is an iron carbide containing three iron atoms for every carbon atom, giving the formula Fe₃C. 145. Pearlite forms due to: A) Eutectic reaction B) Eutectoid reaction C) Peritectic reaction D) Peritectoid reaction Answer: B Reason: At approximately 0.76% carbon and 723°C, austenite decomposes into ferrite and cementite, producing pearlite. 146. The hardest constituent in the Fe–C system is: A) Ferrite B) Austenite C) Cementite D) Pearlite Answer: C Reason: Cementite is a hard and brittle iron carbide, considerably harder than ferrite, austenite, and pearlite.
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  147. Which structureis commonly observed in low-carbon steel? A) Ferrite + Pearlite B) Pearlite only C) Cementite only D) Ledeburite Answer: A Reason: Low-carbon steel is hypoeutectoid, so slow cooling produces proeutectoid ferrite along with pearlite. 148. The microstructure of eutectoid steel after slow cooling consists of: A) Ferrite only B) Pearlite only C) Cementite only D) Austenite only Answer: B Reason: At the eutectoid composition, the entire austenitic structure transforms into pearlite during slow cooling. 149. Which microstructure provides a good balance of strength and ductility? A) Ferrite B) Cementite C) Pearlite D) Ledeburite Answer: C Reason: Pearlite consists of soft, ductile ferrite and hard, strong cementite, giving a useful combination of strength and ductility. 150. The primary purpose of the Fe–C equilibrium diagram is to: A) Predict equilibrium phases and microstructures at different temperatures and carbon contents B) Measure hardness C) Calculate machining speed D) Determine tensile strength directly Answer: A Reason: The Fe–C equilibrium diagram is used to predict the equilibrium phases and resulting microstructures of iron–carbon alloys based on temperature and carbon content. 151. The region enclosed between the liquidus and solidus lines is called the: A) Single-phase liquid region B) Two-phase (Liquid + Solid) region C) Single-phase solid region D) Gas region Answer: B Reason: Both liquid and solid coexist between the liquidus and solidus lines.
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  152. Which lineseparates the single solid solution from the two-solid-phase region? A) Liquidus B) Solidus C) Solvus D) Tie line Answer: C Reason: The solvus line separates one solid phase from two solid phases. 153. The intersection of a tie line with phase boundaries gives: A) Grain size B) Phase compositions C) Cooling rate D) Hardness Answer: B Reason: The tie line endpoints indicate the compositions of the coexisting phases. 154. Which of the following is an equilibrium diagram? A) TTT diagram B) Fe–Fe₃C phase diagram C) CCT diagram D) Stress–strain diagram Answer: B Reason: The Fe–Fe₃C diagram is an equilibrium phase diagram. 155. The primary use of a phase diagram is to determine: A) Cutting speed B) Stable phases at equilibrium C) Tool life D) Surface roughness Answer: B Reason: Phase diagrams predict the equilibrium phases present at different temperatures and compositions. 156. The lever rule is based on the principle of: A) Energy balance B) Mass balance C) Heat transfer D) Momentum balance Answer: B Reason: The lever rule follows conservation of mass. 157. If an alloy lies exactly at the midpoint of a tie line, the phase fractions are: A) 25%–75% B) 75%–25% C) 50%–50% D) 10%–90% Answer: C Reason: Equal lever arms produce equal phase fractions.
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  158. The farthera composition is from a phase boundary, the ______ the amount of that phase. A) Smaller B) Larger C) Equal D) Zero Answer: B Reason: The opposite lever arm determines the phase fraction. 159. Which graphical construction is essential for applying the lever rule? A) Vertical line B) Tie line C) Cooling curve D) Stress–strain curve Answer: B Reason: A tie line at constant temperature is required. 160. The lever rule is NOT applicable in: A) Liquid + Solid region B) α + β region C) Single-phase region D) Two-phase region Answer: C Reason: Lever rule is valid only when two phases coexist. 161. A lamellar microstructure observed under a microscope indicates: A) Ferrite B) Pearlite C) Austenite D) Cementite Answer: B Reason: Pearlite consists of alternating lamellae of ferrite and cementite. 162. Which constituent appears white in a properly etched steel micrograph? A) Ferrite B) Pearlite C) Cementite D) Martensite Answer: A Reason: Ferrite is lightly etched and appears white or bright. 163. Pearlite generally appears: A) White B) Dark C) Transparent D) Blue Answer: B Reason: Pearlite etches darker due to its lamellar structure.
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  164. Grain boundariesbecome visible after: A) Machining B) Polishing C) Etching D) Annealing Answer: C Reason: Etching attacks grain boundaries preferentially. 165. Which specimen preparation step removes scratches before etching? A) Casting B) Polishing C) Rolling D) Forging Answer: B Reason: Polishing produces a mirror finish. 166. A material requiring high ductility should contain more: A) Cementite B) Ferrite C) Ledeburite D) Carbides Answer: B Reason: Ferrite is soft and ductile, whereas cementite and carbides are hard and brittle. 167. High-carbon steel is preferred for cutting tools because of its: A) High ductility B) High hardness C) Low density D) High conductivity Answer: B Reason: High carbon content increases hardness and wear resistance, which are essential for cutting tools. 168. Brass is widely used in plumbing fittings due to its: A) Corrosion resistance B) Low melting point C) Brittleness D) High carbon content Answer: A Reason: Brass has good resistance to atmospheric and water corrosion and also provides good machinability. 169. Bronze is commonly used for: A) Bearings and bushes B) Roofing sheets C) Electrical wires D) Welding electrodes Answer: A Reason: Bronze has good wear resistance, low friction characteristics, and good bearing properties.
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  170. Stainless steelis preferred for surgical instruments because of its: A) High thermal conductivity B) Corrosion resistance C) High density D) Softness Answer: B Reason: Stainless steel resists corrosion and staining and can be cleaned and sterilized effectively. 171. Which constituent contributes most to the hardness of pearlite? A) Ferrite B) Cementite C) Austenite D) Delta ferrite Answer: B Reason: Cementite is a hard and brittle iron carbide, while ferrite is relatively soft and ductile. 172. Slow cooling of steel generally produces: A) Fine grains B) Coarse grains C) No grains D) Glassy structure Answer: B Reason: Slow cooling provides more time for grain growth and diffusion, resulting in a relatively coarse microstructure. 173. Rapid cooling generally results in: A) Finer microstructure B) Coarser microstructure C) Larger grains D) Increased segregation Answer: A Reason: Rapid cooling limits diffusion and transformation time, restricting grain growth and producing a finer structure. 174. The equilibrium diagram assumes: A) Rapid cooling B) Equilibrium (very slow cooling) C) Quenching D) Normalizing Answer: B Reason: Phase diagrams represent equilibrium phase relationships obtained under conditions where sufficient time is available for diffusion and transformation. 175. Which constituent provides the highest toughness? A) Ferrite B) Pearlite C) Cementite D) Ledeburite
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  Answer: A Reason: Ferriteis soft and ductile and can absorb considerable deformation before fracture. 176. Which phase has the highest carbon solubility? A) Ferrite B) Austenite C) Cementite D) Pearlite Answer: B Reason: The FCC structure of austenite can accommodate much more carbon than the BCC structure of ferrite. 177. Which constituent is a compound rather than a phase mixture? A) Pearlite B) Ferrite C) Cementite D) Ledeburite Answer: C Reason: Cementite is a definite iron-carbon compound with the chemical formula Fe₃C, whereas pearlite and ledeburite are mixtures of phases. 178. Which constituent is formed by a eutectoid reaction? A) Ledeburite B) Pearlite C) Austenite D) Delta ferrite Answer: B Reason: At the eutectoid composition, austenite transforms into ferrite and cementite, producing pearlite. 179. Which constituent forms at the eutectic composition in the Fe–C system? A) Pearlite B) Ferrite C) Ledeburite D) Martensite Answer: C Reason: At approximately 4.3% carbon and 1147°C, liquid transforms into austenite and cementite, forming ledeburite. 180. Which constituent contains alternating ferrite and cementite plates? A) Austenite B) Pearlite C) Cementite D) Ferrite Answer: B Reason: Pearlite is a lamellar mixture of ferrite and cementite formed during the eutectoid transformation.
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  181. Carbon actsas a ______ atom in steel. A) Substitutional B) Interstitial C) Replacement D) Surface Answer: B Reason: Small carbon atoms occupy the spaces between iron atoms in the iron crystal lattice rather than replacing iron atoms. 182. Which alloy is an example of a substitutional solid solution? A) Brass B) Steel C) Cast iron D) White cast iron Answer: A Reason: Brass contains zinc atoms that replace some copper atoms in the crystal lattice because their atomic sizes are relatively similar. 183. Which alloy is an example of an interstitial solid solution? A) Brass B) Bronze C) Steel D) Cupronickel Answer: C Reason: Small carbon atoms occupy interstitial positions within the iron lattice. 184. The hardest phase in the Fe–C system is: A) Ferrite B) Austenite C) Cementite D) Pearlite Answer: C Reason: Cementite (Fe₃C) is a very hard and brittle iron carbide. 185. The softest phase in steel is: A) Cementite B) Ferrite C) Pearlite D) Ledeburite Answer: B Reason: Ferrite contains very little carbon and is relatively soft and ductile. 186. Pearlite is a ______ constituent. A) Single-phase B) Two-phase mixture C) Liquid D) Ceramic Answer: B Reason: Pearlite consists of two phases: ferrite and cementite.
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  187. Which lineindicates the completion of solidification? A) Liquidus B) Solidus C) Solvus D) Tie line Answer: B Reason: Below the solidus temperature, the alloy is completely solid; between liquidus and solidus, both liquid and solid phases coexist. 188. Which line indicates the beginning of solidification? A) Liquidus B) Solidus C) Solvus D) Vertical axis Answer: A Reason: On cooling, the first solid phase begins to form when the alloy crosses the liquidus line. 189. Which invariant reaction produces two solid phases from one liquid phase? A) Peritectic B) Eutectic C) Eutectoid D) Peritectoid Answer: B Reason: In a eutectic reaction, one liquid phase transforms simultaneously into two solid phases at a fixed temperature and composition. 190. Which invariant reaction produces two solid phases from one solid phase? A) Eutectic B) Eutectoid C) Peritectic D) Monotectic Answer: B Reason: In a eutectoid reaction, one solid phase transforms into two different solid phases, as in austenite transforming into ferrite and cementite. 191. The primary objective of alloying is to: A) Reduce cost only B) Improve material properties C) Reduce melting point only D) Change colour only Answer: B Reason: Alloying is used to modify properties such as strength, hardness, toughness, corrosion resistance, wear resistance, and machinability.
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  192. Metallography isthe study of: A) Heat treatment B) Metal microstructures C) Welding D) Casting defects Answer: B Reason: Metallography involves preparing, examining, and interpreting the microstructure of metals and alloys, usually using optical or electron microscopy. 193. The study of phase diagrams is essential because it helps engineers to: A) Predict equilibrium phases and microstructures B) Calculate machining time C) Measure surface roughness D) Determine cutting speed Answer: A Reason: Phase diagrams enable engineers to predict the equilibrium phases and microstructures formed at different temperatures and compositions, which is fundamental to alloy design, heat treatment, and material selection.