71. Hardness of upper bainite (acicular structure) is about
A.RC 65
B.RC 48
C.RC 57
D.RC 80

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72. Carbon in iron is an example of
A.Substitutional solution
B.Interstitial solid solution
C.Intermetallic compounds
D.All of the above

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73. Brass (alloy of copper and zinc) is an example of
A.Substitutional solid solution
B.Interstitial solid solution
C.Intermetallic compounds
D.All of the above

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74. Which is false statement about annealing. Annealing is done to
A.Relieve stresses
B.Harden steel slightly
C.Improve machining characteristic
D.Soften material

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75. Argentite is the principal ore or raw material for
A.Aluminium
B.Silver
C.Zinc
D.Lead

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76. Hardness of lower bainite (tempered martensite) is about
A.RC 65
B.RC 48
C.RC 57
D.RC 80

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77. Sphalerite is the principal ore or raw material for
A.Zinc
B.Silver
C.Tin
D.Magnesium

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