Explore topic-wise MCQs in Phase Transformation.

This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Phase Transformation knowledge and support exam preparation. Choose a topic below to get started.

1.

During carburization to obtain a twofold increase in penetration requires a __________

A. Fourfold decrease in time
B. Threefold increase in time
C. Fourfold increase in time
D. Twofold increase in time
Answer» D. Twofold increase in time
Discussion
2.

After a time t=2* ( is taken as relaxation time), the amplitude of concentration decreases by__

A. 1/e<sup>2</sup>
B. 1/e
C. 1/2
D. 1/3
Answer» B. 1/e
Discussion
3.

Diffusion coefficient of B-atom is given as 2.5m2/s and L value is given as 2m, calculate the relaxation time?

A. 0.161
B. 0.201
C. 0.321
D. 0.404
Answer» B. 0.201
Discussion
4.

Which of the following equation is related to Fick s second law_________

A. J = D*( C/ X)
B. ( C/ X) = D*( <sup>2</sup>C/ X<sup>2</sup>)
C. J = D*( C/ T)
D. C/ T=k*( C/ X) (k some constant)
Answer» C. J = D*( C/ T)
Discussion
5.

On average, the fraction of atoms with an energy of G or more than the mean energy is given by_____

A. Exp (- G/RT)
B. Exp (RT/ G)
C. Exp ( G/RT)
D. Exp (RT/ G)
Answer» B. Exp (RT/ G)
Discussion
6.

The activation enthalpy for interstitial diffusion increases as the size of the interstitial atom increases.

A. False
B. True
Answer» C.
Discussion
7.

To move an interstitial atom to an adjacent interstice, the atoms of the parent lattice must be forced apart into higher energy positions. The work that must be done to accomplish this process causes____

A. An increase in free energy of system
B. A decrease in free energy of system
C. An increase in internal energy
D. A decrease in internal energy
Answer» D. A decrease in internal energy
Discussion
8.

During decarburization of steel, the surface concentration is reduced to a very low value.

A. True
B. False
Answer» B. False
Discussion
9.

The rest positions of the interstitial atoms are positions of____________

A. Minimum potential energy
B. Maximum potential energy
C. Minimum kinetic energy
D. Maximum internal energy
Answer» B. Maximum potential energy
Discussion
10.

Particularly violent oscillation of an interstitial atom or some chance coincidence of the movement of the matrix and interstitial atoms will result in a jump.

A. True
B. False
Answer» B. False
Discussion
11.

In a hexagonal lattice on average, an interstitial atom jumps 6 times per second and that each jump is in a random direction, then the probability of the atom jumping to every one of the six adjacent sites is given by___________

A. 1
B. 1/6
C. 1/2
D. Cannot be predicted
Answer» E.
Discussion
12.

The concentration of oxygen at the inner surface of the vessel is maintained at a level C depending on the pressure in the vessel, while the concentration at the outer surface is reduced to zero by the escape of oxygen to the surroundings. A steady state will eventually be reached when the concentration everywhere reaches a constant value. Provided D is independent of concentration there will be a single concentration gradient in the wall and the thickness of the wall is L, the flux is given by________________

A. DC/L
B. DL/C
C. CL/D
D. DC/L + K (some constant)
Answer» B. DL/C
Discussion
13.

Assume that on average an interstitial B-atom jumps 10 times per second. The distance between the plane is given by 2m. Then, calculate the coefficient of diffusion of B atoms? (In m2/s)

A. 20/3
B. 40/3
C. 10/3
D. 6
Answer» B. 40/3
Discussion
14.

Which of the following equation is related to Fick s first law of diffusion?

A. J = D*( C/ X)
B. J = D*( C/ t)
C. J = D*(dC/dt)
D. J = D*(dC/dx)
Answer» B. J = D*( C/ t)
Discussion
15.

If plane (1) contains 5 B-atoms per metre square, calculate the number of atoms that will jump from plane (1) to (2) in 1s? (Assume that on average, an interstitial atom jumps 6 times per second)

A. 5
B. 6
C. 1
D. 2
Answer» B. 6
Discussion