Material Science & Metallurgy - May 2016

Mechanical Engg. (Semester 3)

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) Define APF. With a neat sketch obtain an expression for density packing factor of HCP structure.(8 marks) 1(b) Give brief classification of crystal defects. Explain them briefly.(6 marks) 1(c) List the factors affecting diffusion. Explain them briefly.(6 marks) 2(a) Define engineering stress and strain and true stress and true strain. Establish the relationship between true strain and engineering strain.(7 marks) 2(b) List and explain the mechanical properties in elastic and plastic region.(7 marks) 2(c) Define CRSS? Obtain the expression for the same.(6 marks) 3(a) Explain: i) Cup and cone fracture ii) Ductile to Brittle transition.(8 marks) 3(b) What are the different fatigue protection methods? Explain briefly.(6 marks) 3(c) What is stress relaxation? Derive an expression for the same.(6 marks) 4(a) What is solid solution? With neat sketches explain different types of solid solution.(6 marks) 4(b) Explain Hume-Rothary rules and Gibbs phase rule.(6 marks) 4(c) Differentiate Homogeneous and Hetrogeneous nucleation. How do you compute the critical size of nucleus and activation energy for the homogeneous nucleation?(8 marks) 5(a) A binary alloy of composition 60%A and 40%B consists two phases namely liquid and solid at a particular temperature. The composition of solid phase is 23%B and that of liquid phase is 68%B. Estimate the amount of soild and liquid phases is the alloy.(8 marks) 5(b) Draw Fe - Fe₃C diagram and show all phases, fields, temperature and composition. Write all invariant reactions. Also explain the solidification of steel containing 0.4%C.(12 marks) 6(a) Explain TTT digram (for 0.8%C steel) by supper imposing the cooling curves on it.(12 marks)

Differentiate between:

6(b)(i) Austempering and martempering(4 marks) 6(b)(ii) Annealing and Normalising(4 marks) 7(a) Give composition, micro structure, properties and applications of different types of cast - Irons.(12 marks) 7(b) Write a note on Magnesium alloys and Titanium alloys.(8 marks) 8(a) Define composite. Give brief classification of composites.(6 marks) 8(b) With neat sketch explain production of composites, by pultrusion process.(8 marks) 8(c) Enumerate the merits, demerits and application of composites.(6 marks)