Material Science & Metallurgy - Dec 2015
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 the terms space lattice, until cell and APF.(6 marks) 1 (b) Cr has an atomic radius of 0.125mm, a BCC crystal structure and an atomic weight of 52g/mol. Calculate the density. (Avogadro number is 6.023×1023).(6 marks) 1 (c) Differentiate between edge and screw dislocation with neat sketches.(8 marks) 2 (a) Draw the stress-strain diagram of Aluminium and explain the following properties
i) Proof stress ii) Toughness(5 marks) 2 (b) A 10mm aluminium alloy rod is subjected to a 6kN tensile load. If the diameter of the rod is 9mm at this load determine the engineering stress, engineering strain, true stress and true strain.(8 marks) 2 (c) Distinguish between slip and twinning with neat sketch.(7 marks) 3 (a) Define the following terms with sketches.
i) Fatigue limit
ii) Fatigue strength
iii) Fatigue life.(6 marks) 3 (b) Explain the different stages of creep with a neat sketch of the creep curve.(8 marks) 3 (c) Compare ductile and brittle fracture with neat sketches.(6 marks) 4 (a) What is a solid solutions? Explain the Hume-Rothary rules for the formation of substitutional solid solution with examples.(8 marks) 4 (b) Compare homogeneous and heterogeneous nucleation with sketches.(6 marks) 4 (c) Write short notes on intermediate phases.(6 marks) 5 (a) Give the three invariant reactions of the Fe-C system indicating the temperature and composition.(6 marks) 5 (b) Explain the solidification of hypoeutectoid steel containing 0.3%C indicating the micro strictures at different stages with a neat sketch.(8 marks) 5 (c) Construct a phase diagram for two metals completely soluble in the liquid state but partially soluble in the solid state. Give any two examples.(6 marks) 6 (a) Draw the CCC diagram and explain briefly for a plain carbon eutectoid steel.(7 marks) 6 (b) Explain age hardening of Al-Cu alloy with a sketch.(8 marks) 6 (c) Distinguish between process annealing and speroidising with a sketch.(5 marks) 7 (a) Compare SG iron, Grey cast Iron and white caste Iron with respect to composition, microstructure, properties and applications.(12 marks) 7 (b) Write short notes on the following:
i) Al-Si alloys
ii) Brasses(8 marks) 8 (a) Define a composite. What is the role of matrix in a composite materials?(6 marks) 8 (b) Explain with a neat sketch the pultrusion process or hand layup process.(8 marks) 8 (c) Give three commonly used matrix materials and reinforcement fibers used in the Production of FRP'S.(6 marks)