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:
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:
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)