Material Science (Deformation of Materials)

1. Burger’s vector of an edge dislocation is
(1) parallel to dislocation line
(2) perpendicular to dislocation line
(3) at any angle with dislocation line including 0 and 90°
(4) none of the above 
(2)
2. Yield point in mild steel occurs because
(1) carbon atom occupy the vacancy line just below the dislocation and anchor dislocation by reducing
its energy.
(2) slip is promoted by carbon atoms to take place in several parallel plans simultaneously.
(3) carbon atoms form Fe3C with iron
(4) none of the above 
(1)
3. If ASTM grain size number 7 corresponds to grain diameter of 0.03 mm, ASTM 4 corresponds to
(1) 0.36 mm 
(2) 0.085 mm 
(3) 0.055 mm 
(4) 0.008 mm 
(2)
4. The mean grain diameter corresponding to ASTM number = –0.5 is
(1) 0.87 mm 
(2) 0.43 mm 
(3) 0.24 mm 
(4) 0.13 mm 
(2)
5. Strain ageing in mild steel causes
(1) material to behave in brittle manner
(2) material to lose its ultimate tensile strength
(3) yield point to recur in alternate loading beyond yielding and unloading
(4) none of the above

6. Recrystallization temperature is the temperature at which recrystalliztion just reaches completion in
(1) 3 hr 
(2) 2 hr 
(3) 1 hr 
(4) 1/2 hr 
(3)
7. The recrystallization temperature for brass alloy is about
(1) 1350°C 
(2) 770°C 
(3) 660°C 
(4) 450°C 
(4)
8. If Tm is absolute melting temperature, then the recrystallization temperature for pure metals in terms of Tm is normally
(1) 0.7 T
(2) 0.9 T
(3) 0.5 T
(4) 0.3 T

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(4)

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