A steel specimen containing 0.2 wt.% C is carburized in an atmosphere that maintains a carbon content of 1.2 wt.% C at the surface of the specimen.
Given:
For carbon diffusion in austenite: D₀ = 2.0 × 10^-5 m²/s
Activation energy for diffusion, Q = 142 kj/mol

y	erf(y)
0.85	0.7707
0.90	0.7970
0.95	0.8209

What is the depth (in (μm) from the surface of the specimen at which a composition of 0.4wt.% C is obtained after carburizing at 870°C for 10 h?

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