Engineering Materials

61. DuraJomin contains

1. 94% aluminium, 4% copper and 0.5% Mn, Mg, Si and Fe
2. 92.5% aluminium, 40% copper, 2% nickel, and 1.5% Mg
3. 10% aluminium and 90% copper
4. 90% magnesium and 9% aluminium with some copper
5. 94% aluminium and 6% tin.

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62. Elinvar, an alloy used in precision instruments, hair springs for watches, etc. contains the following element as principal alloying element

1. iron
2. copper
3. aluminium
4. zinc
5. nickel.

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63. Eutectoid steel contains following percentage of carbon

1. 0.02%
2. 0.3%
3. 0.63%
4. 0.8%
5. 1.2%.

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64. Ferromagnetic alpha iron exists in temperature range of

1. below 723°C
2. 770 – 910°C
3. 910-1440°C
4. 1400-1539°C
5. above 1539°C.

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65. Following elements have face-centred cubic structure

1. gamma iron (910° to 1400°C), Cu, Ag, Au, Al, Ni, Pb, Pt
2. Mg, Zn, Ti, Zr, Br, Cd
3. a iron (below 910°C and between 1400 to 1539°C), W
4. all of the above
5. none of the above.

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66. For the allotropic forms of iron, the points of arrest are

1. the points where no further change oc-curs
2. constant for all metals
3. the points where there is no further flow of metal
4. the points of discontinuity
5. the points where major changes take place.

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67. Foundry crucible is made of

1. mild steel
2. german silver
3. lead
4. cast iron
5. graphite.

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68. Free cutting steels

1. are used where ease in machining is the criterion
2. contain carbon in free form
3. require least cutting force
4. do not exist
5. can be cut freely even under adverse conditions.

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69. Gamma iron exits at following temperature

1. room temperature
2. near melting point
3. between 1400°C and 1539°C
4. between 910°C and 1400°C
5. none of the above.

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70. German silver contains

1. 1% silver
2. 2.5% silver
3. 5% silver
4. 10% silver
5. 100% silver.

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