Engineering Materials

121. Recrystallisation temperature can belowered by

  1. purification of metal
  2. grain refinement
  3. working at lower temperature
  4. all of the above
  5. none of the above.

Correct answer: (D)
all of the above

122. Recrystallization temperature is one

  1. at which crystals first start forming from molten metal when it is cooled
  2. at which new spherical crystals first begin to form from the old deformed one when a strained metal is heated
  3. at which change of allotropic form takes place
  4. at which crystals grow bigger in size
  5. at which crystals are destroyed on heating.

Correct answer: (B)
at which new spherical crystals first begin to form from the old deformed one when a strained metal is heated

123. Slow plastic defomiation of metals under a constant stress is known as

  1. creep
  2. fatigue
  3. endurance
  4. plastic deformation
  5. non-plastic deformation.

Correct answer: (A)
creep

124. Solder is an alloy consisting of

  1. tin, antimony, copper
  2. tin and copper
  3. tin and lead
  4. lead and zinc
  5. lead and copper.

Correct answer: (B)
tin and copper

125. Steel contains

  1. 80% or more iron
  2. 50% or more iron
  3. alloying elements like chromium, tungsten nickel and copper
  4. elements like phosphorus, sulphur and silicon in varying quantities
  5. high quantities of sulphur.

Correct answer: (B)
50% or more iron

126. Steel made from phosphatic iron is

  1. brittle
  2. hard
  3. ductile
  4. tough
  5. malleable.

Correct answer: (A)
brittle

127. Stress relaxation is- the phenomenon

  1. in which parts are not loaded
  2. in which stress remains constant on in-creasing load
  3. in which deformation tends to loosen the joint and produces a stress reduced
  4. stress reduces on increasing load
  5. none of the above.

Correct answer: (C)
in which deformation tends to loosen the joint and produces a stress reduced

128. Structural steel contains following principal alloying elements

  1. nickel, chromium and manganese
  2. tungsten, molybdenum and phosphorous
  3. lead, tin, aluminium
  4. zinc, sulphur, and chromium
  5. none of the above.

Correct answer: (A)
nickel, chromium and manganese

129. Sulphur in pig iron tends to make it

  1. hard'
  2. soft
  3. ductile
  4. tough
  5. malleable.

Correct answer: (A)
hard'

130. Sulphur in steel

  1. acts as deoxidiser
  2. reduces the grain size
  3. decreases tensile strength and hardness
  4. lowers the toughness and transverse ductility
  5. increases hardness.

Correct answer: (D)
lowers the toughness and transverse ductility

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