E E4850 Pages: 2
Reg No.: Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD/FOURTH SEMESTER B.TECH DEGREE EXAMINATION, APRIL 2018

Course Code: ME210
Course Name: METALLURGY AND MATERIALS ENGINEERING

(MC, MP, MA, ME, PE)
Max. Marks: 100 Duration: 3 Hours
PART A
Answer any three full questions, each carries 10 marks. Marks

1 8) Explain with neat sketches the mechanism of dislocation and twinning as related (4) to
plastic deformation.

b) What are Miller Indices? Sketch (101), (110), (011) planes on a cubic unit cell. (6)

2 9) Define critically resolved shear stress. (3) 0) A single metal crystal is oriented such that
the normal to the slip plane and the (4) slip direction are at angles of 43.1° and 47.9°,
respectively, with the tensile axis. If the critical resolved shear stress is 20.7 MPa, will an
applied stress of 45 MPa cause the single crystal to yield? If not, what stress will benecessary?

௦) Is iron an allotropic metal? Explain. (3)

3 9) How are yield strength and grain size of a crystal related? (3) b) Yield strength of mild
steel with an average grain size of 0.0S5mm is 138MPa and (3) with a grain size of 0.007mm
is 276MPa. What will be the average grain size for the same steel for yield strength of
207MPa?

c) What is the significance of Burgers vector and Frank Read source in dislocation?
(4)

4 2) Explain the Fick’s laws of diffusion. (4) b) An iron plate is exposed to a carburising

atmosphere on one side and a (6)
decarburising atmosphere on other side at 720°C. If a steady state condition is
achieved, calculate the diffusion flux of carbon through the plate if the
concentrations of carbon at positions of 6mm and 11mm beneath the carburising
surface are 1.22 kg/m? and 0.82 kg/m? respectively. Assume a diffusion coefficient
of 3.2 x 10 !! m’/s at this temperature.

PART B
Answer any three full questions, each carries 10 marks.

5 93) Sketch and label the Iron-Carbon equilibrium diagram and explain the three (6) equilibrium
reactions in it.
b) Copper (melting point 1083°C) and silver (melting point 961°C) form an alloy (4)
system which has partial solubility in the solid state. The mutual solubility of silver
in copper is 7.9% and that of copper in silver is 8.8% at a eutectic temperature of
779°C. The eutectic alloy has 71.9% silver. Sketch and label the phase diagram for
Cu-Ag alloy system.

6 8) Most cast alloys are reheated to a temperature below solidus after the solidification is (3)
completed. Why?

b) What is the significance of critical cooling rate for an iron-carbon alloy system? (3)

Page 1 of 2