Material Science & Metallurgy - Dec 2014
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) Classify in detail the different types of crystal imperfections. Explain with a neat sketch the edge dislocation.(8 marks) 1 (b) Illustrate steady state and non-steady state diffusion.(6 marks) 1 (c) Steel gear, having carbon content of 0.2% is to be gas carburized to achieve carbon content of 0.90% at the surface and0.4% at 0.5mm depth from the surface. If the process is to be carried out at 927°C, find the time required for carburization. Take diffusion co-efficient of carbon in given steel -1.28 × 10-11 mt2/sec. Given data:
i) The pouring temperature
ii) The Solidification temperature
iii) The Super heat
iv) The Cooling rate, just before solidification begins.
v) The total solidification time.
vi) The local solidification time.
img(8 marks) 5 (a) Draw the Iron-Carbon equilibrium diagram and label it. Show the invariant points on it.Write the reactions occurring at these points indicating the temperature and composition of each phase.(10 marks) 5 (b) Two metals A and B have their melting points at 900°C and 800°C respectively. The alloy pair forms an eutectic at 600°C of composition 60% B. They have unlimited liquid solubilities. The solid solubility of A in B is l0% and that of B in A is 5% at eutectic temperature and remains constant till 0°C. Draw the phase diagram and label all the fields.Find the amount of liquid and solid phases in an alloy of 20Yo B at 650°C(10 marks) 6 (a) Draw the TTT diagram for eutectoid steel and explain the different micro structure obtained at various cooling rates.(10 marks) 6 (b) Mention the types of heat treatment process. Explain with a suitable sketch the full annealing process.(10 marks) 7 (a) Explain the structure, composition and properties of gray cast iron.(6 marks) 7 (b) Briefly explain the effect of alloying elements on properties of steel.(6 marks) 7 (c) Write a short note on the copper and its alloys.(8 marks) 8 (a) Define composite material. Give the classification based on matrix, geometry of reinforcement and construction. Also explain briefly the production of filament winding process with a neat sketch(10 marks) 8 (b) Explain with a neat sketch the pultrusion process and mention its applications.(10 marks)