The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10^-11 m^-2 s^-1. Assume the diffusion couple to be infinitely long.

Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$

A plastically deformed metal crystal at low temperature exhibits wavy slip line pattern due to

A. Dislocation pile-up

B. Large number of slip systems

C. Low stacking faultenergy

D. Dislocation climb

Which of the following microstructures of the eutectic is not observed in binary alloys?

A. Lamellar

B. Widmanstatten

C. Acicular

D. Nodular

Upon addition of sodium oxide to molten silicate slag, the viscosity of the slag

A. decreases because the oxygen ions supplied by the sodium oxide break the chain structure of the silicate slag

B. increases because the oxygen ion supplied by the sodium oxide further add to the oxygen network in the slag

C. remains unaffected because fundamentally one can not distinguish between the oxygen ions supplied by the sodium oxide and those already present in the slag

D. remains unaffected because the oxygen ions fill up the holes and vacancies present in the liquid slag

A 0.4 wt% C steel is austenitised at 900°C for 1 hour and heat treated to get different. inicrostructures. Match the following microstructures to the heat treatments.

A. P-4, Q-3, R-2, S-1

B. P-1, Q-2, R-3, S-4

C. P-2, Q-4, R-1, S-3

D. P-2, Q-4, R-3, S-1