Material Science & Metallurgy - Jun 2012

Mechanical Engineering (Semester 4)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Explain the term:
(i) Space lattice
(ii) coordination number
(iii) Atomic packing factor(6 marks) 1 (b) Clearly explain different mechanism of diffusion in solids.(8 marks) 1 (c) With neat sketches,explain vacancy and Schottky imperfection. Calculate the equilibrium number of vacancies per cubic meter for copper at 1000° the energy for vacancy formation is 0.9 eV/atom. The atomic weight and density (at 100°C) for copper are 63.5g/mol and 8.4g/cm³ respectively.(Boltzman's constant = 8.62×10^-5eV/K)(8 marks) 2 (a) Draw Stress - Strain Diagram for a ductile material and explain the salient points.(6 marks) 2 (b) What do you mean by true stress and true strain? A cylindrical specimen of steel having an original diameter of 12.8 mm is tensile tested to fracture and found to have an engineering fracture strength ?_r of 460 MPa. If as cross sectional diameter at fracture is 10.7 mm determine:
i) The ductile in term of percent area reduction
ii) The true at fracture(5 marks) 2 (c) Differentiate between slip and twinning.(7 marks) 3 (a) Explain with sketches the ductile and brittle in materials.(7 marks) 3 (b) Explain the following:
i) S-N diagram
ii) Fatigue properties(6 marks) 3 (c) Define creep. With the help of a neat diagram, explain the three stages of creep.(7 marks) 4 (a) Define nucleation. Distinguish between homogeneous and heterogeneous nucleation.(7 marks) 4 (b) What are solid solutions? Explain the factors governing the formation of substitution solid solution. (7 marks) 4 (c) State and explain Gibb's phase rule. How it can be applied to unary phase diagram? Show that degrees of freedom at a triple point is zero.(6 marks) 5 (a) Draw iron carbon equilibrium diagram and label all phase fields, temperature and composition on it. Discuss the different invariant and draw the microstructure of 0.6%C steel at room temperature.(10 marks) 5 (b) What is a phase diagram? Clearly explain the different prediction that can be made from phase diagram.(10 marks) 6 (a) Explain the construction of TTT diagram.(10 marks) 6 (b) With a neat sketch explain the following heat treatment processes on steel:
i) Annealing
ii) Normalizing (10 marks) 7 (a) Write composition, properties and use of:
i) S.G iron
ii) Malleable cast iron
iii) Grey cast iron (12 marks) 7 (b) Write short notes on:
i) Cupronickel
ii) Bronzes(8 marks) 8 (a) What is a composite material? Discuss the role of matrix and reinforcement in a composite material.(6 marks) 8 (b) Compare MMCs with PMCs.(6 marks) 8 (c) Write a short note on FRPs.(8 marks)