Phase Transformation - Physical Metallurgy - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

In a niobium micro-alloyed steel joined by fusion welding the most likely cause of loss of strength in the heat affected zone (HAZ) is

A

precipitate coarsening and grain growth

B

coarse pearlite and grain boundary precipitation

C

tempered martensite and grain boundary carbide

D

formation of bainite

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2

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

Which one of the following alloy systems exhibits complete solid solubility?

A

Cu-Ni

B

Fe-Cu

C

Pb-Sn

D

Cu-Zn

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3

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

In the TTT diagram for the eutectoid carbon steel, the nose of the characteristic C-curve is at 550 °C. This C-shape implies delayed transformation both above and below 550 °C. The delay at lower temperatures is due to low diffusivity. The delay at higher temperatures is due to

A

low driving force for transformation

B

low mobility of dislocations

C

low concentration of vacancies

D

low diffusivity

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4

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

The maximum amount of proeutectic austenite that can form in an iron-carbon alloy containing 3.5% carbon is [Given: The maximum solubility of carbon in γ-iron is 2.11%]

A

24.80%

B

36.53%

C

67.87%

D

72.52%

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5

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

Match each phase in group I with a description in group II.

Group-I	Group-II
(P) ε - Carbide	(1) a three-component eutectic of iron, iron-carbide, iron-phosphite found in cast iron
(Q) Sigma phase	(2) an embrittling compound found in ferritic stainless steels
(R) δ – Ferrite	(3) obtained on tempering of hardened steels
(S) Steadite	(4) responsible for causing the weld-deposit on austenitic stainless steels to be slightly magnetic

A

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

B

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

C

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

D

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

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6

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

In normalized hypoeutectoid plain carbon steels, how do the fraction of proeutectoid ferrite (\(f\)) and yield strength (\(\sigma_y\)) change with increasing carbon content?

A

\(f\) increases and \(\sigma_y\) decreases

B

both \(f\) and \(\sigma_y\) increase

C

both \(f\) and \(\sigma_y\) decrease

D

\(f\) decreases and \(\sigma_y\) increases

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7

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

Identify the correct statement about manganese in steels from the following.

A

it decreases hardenability

B

it makes the steel susceptible to hot-shortness

C

it is a strong austenite stabilizer

D

it decreases hardness of martensite

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8

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

The size r*^* of the critical cluster is given by:

A

-2γ/ΔG_v

B

-ΔG_v/2γ

C

-π·γ/ΔG_v

D

-γ/(π·ΔG_v)

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9

2007 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2007

If ΔG_v = 3.0 × 10⁷ J m^-3, and γ = 3.3 × 10^-3 J m^-2, the number of atoms in the critical cluster is approximately (Given: the solid is an FCC crystal with a lattice parameter of 0.495 nm)

A

95

B

550

C

1470

D

20700

Check answer

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10

2008 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2008

The time taken for 50% recrystallization of cold worked Al is 100 hours at 500 K and 10 minutes at 600 K. Assuming Arrhenius kinetics, the activation energy for recrystallization in kJ mol^-1 is

A

50

B

80

C

160

D

320

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11

2008 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2008

Match the processes in Group 1 with the physical principles in Group 2

A

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12

2008 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2008

Match the unit processes in Group 1 with the objectives in Group 2

A

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13

2008 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2008

An annealed hypoeutectoid steel has 10% of proeutectoid ferrite at room temperature. The eutectoid carbon content of the steel is 0.8%. The carbon content in the steel in percent is

A

0.58

B

0.68

C

0.72

D

0.78

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14

2009 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2009

An annealed plain carbon steel, showing fully pearlitic microstructure, has a carbon content of

A

0.01 wt %

B

0.20 wt %

C

0.77 wt %

D

1.20 wt %

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15

2009 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2009

As per the TTT diagram, bainite will form in eutectoid plain carbon steel when heated to 850 °C followed by

A

air-cooling to room temperature

B

isothermal holding between eutectoid temperature and the nose

C

quenching to room temperature

D

isothermal holding between the nose and the Mₛ temperature

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16

2009 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2009

According to Hume-Rothery rules, extensive solid solubility between elements X and Y is promoted by the two factors in the following list :
P. Same crystal structure of X and Y
Q. Large atomic size difference (> 20 %) between X and Y
R. Same valence of X and Y
S. Large difference in melting points of X and Y

A

P, Q

B

P, R

C

Q, S

D

P, S

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17

2009 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2009

A Pb-Sn hypo-eutectic alloy is slowly cooled from the liquid state to room temperature. The composition of the alloy whose microstructure consists of 25 wt% lamellar constituent is

A

Pb - 29.2 wt % Sn

B

Pb - 35.5 wt % Sn

C

Pb - 40.8 wt % Sn

D

Pb - 61.9 wt % Sn

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18

2010 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2010

In heterogeneous nucleation, the radius of the critical nucleus does NOT depend on

A

contact angle

B

undercooling

C

the surface energy of the interface between the product and parent phases

D

enthalpy change per unit volume of the product phase

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19

2010 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2010

Driving force for grain growth after completion of recrystallization is

A

stored energy of cold work

B

vacancy concentration

C

dislocation density in the crystal

D

grain boundary curvature

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20

2010 · Metallurgical Engineering · Physical Metallurgy · Phase Transformation

Metallurgical Engineering (MT) 2010

A recrystallization process is 20% complete after 45 s and 85% complete after 75 s. Assuming Avrami kinetics, the value of Avrami exponent “n” is

A

4.19

B

3.12

C

2.42

D

1.34

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