JNTU PAPERS,B-Tech,I- Semester,Physical Metallurgy, November 2008

JNTU PAPERS

JNTU,B.Tech,I- Semester, Physical Metallurgy, November 2008

 (Metallurgy & Material Technology)

SET-3

1.(a) Name different types of electron microscopes and highlight the salient features

associated with them.

(b) Explain construction and working of a compound microscope.

 

2. (a) Prove that the packing factor for HCP cell is 0.74%.

(b) One of the atoms of manganese has an atomic radius of 1.12 Ao and a lattice

parameter of 2.930A and a packing factor of 0.479. How many atoms are in the unit cell.

 

3.(a) What is a solid solution? Give the classification and explain the rules for the formation of solid solutions.

(b) Explain why atomic size difference is only 4.2% still Zn can dissolve up to

38.4% in Cu?

 

4. (a) If a pure metal is cast into

i. A chill-mould and

ii. A sand mould. Explain giving reasons how the resultant micro structure would differ.

(b) Draw the cooling curves for a short freezing range alloy and long freezing range alloy and explain the salient points in it.

 

5. (a) What is allotrophy? What is allotrophic transformation? Give any three

examples which show allotrophic transformation and explain them.

(b) Explain the allotropic transformation of Iron.

 

6. Explain Why ?

(a) Delta – Fe dissolves more carbon than Alpha-Fe when both have same crystal structure.

(b) Ac3 temperature decreases with the increase of carbon content.

(c) Ar3 decreases with the increase of pressure in Iron.

(d) Is Fe – Fe3C diagram an Equilibrium or a non Equilibrium diagram.

 

7. (a) How are the critical temperatures of steel on heating and cooling designated.

(b) If a steel is heated to temperature just above its MS temperature, and then

quenched, Martensite does not form. Explain why?

(c) ‘When martensite form, expansion occurs’. Explain why?

(d) Explain why martensite is not always hard and brittle.

 

8. (a) What are MS and Mf temperatures? Explain in detail. What is the significance of the above?

(b) Distinguish between CCT & TTT diagrams

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