Crystal Imperfections - Physical Metallurgy - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2007

The equilibrium vacancy concentration in copper is 588 ppm at 1000°C and 134 ppm at 800°C. The molar enthalpy of vacancy formation is

A

49 kJ mol\(^{-1}\)

B

84 kJ mol\(^{-1}\)

C

168 kJ mol\(^{-1}\)

D

243 kJ mol\(^{-1}\)

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2

2007 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2007

In a cubic crystal with lattice parameter \(a\), the dislocation reaction that is vectorially correct and energetically feasible is

A

\(\frac{a}{2}[1\bar{1}\bar{1}] + \frac{a}{2}[1\bar{1}1] \rightarrow a[100]\)

B

\(\frac{a}{2}[110] + \frac{a}{2}[1\bar{1}0] \rightarrow a[110]\)

C

\(\frac{a}{6}[10\bar{1}] + \frac{a}{6}[\bar{1}21] \rightarrow \frac{a}{3}[111]\)

D

\(\frac{a}{2}[0\bar{1}1] \rightarrow \frac{a}{6}[2\bar{1}1] + \frac{a}{6}[12\bar{1}]\)

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3

2008 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2008

In Cu-Al phase diagram, the solubility of Al in Cu at room temperature is about 10% and that of Cu in Al is less than 1%. The Hume-Rothery rule that justifies this difference is

A

size factor

B

electro-negativity

C

structure

D

valency

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4

2008 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2008

The stacking sequence of close packed planes with a stacking fault is

A

\(a b c a b c a b c\)

B

\(a b a b a b a b a b\)

C

\(a b c a c a b c a b\)

D

\(a b c a b a c b a\)

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5

2008 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2008

The slip directions on a \((1 \bar{1} \bar{1})\) plane of a fcc crystal are

A

\([\bar{1}01], [01\bar{1}], [1\bar{1}0]\)

B

\([10\bar{1}], [\bar{1}10], [\bar{1}0\bar{1}]\)

C

\([0\bar{1}1], [\bar{1}\bar{1}0], [0\bar{1}1]\)

D

\([0\bar{1}1], [0\bar{1}\bar{1}], [\bar{1}10]\)

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6

2009 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2009

The Miller indices of the plane PQRS, shown in the unit cell, are

A

(111)

B

(1̅21)

C

(1̅10)

D

(100)

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7

2009 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2009

A defect that is bounded by two mirror planes is

A

twin

B

stacking fault

C

grain boundary

D

edge dislocation

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8

2011 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2011

Which one of the following reactions in fcc/bcc crystals with lattice parameter \( a \) is energetically favorable?

A

\(\frac{a}{2}[1\bar{1}0] + \frac{a}{2}[0\bar{1}1] \)

B

\(\frac{a}{2}[\bar{1}10] + \frac{a}{2}[\bar{1}10] \)

C

\(\frac{a}{2}[111] + \frac{a}{2}[11\bar{1}] \)

D

\(\frac{a}{2}[111] + \frac{a}{2}[\bar{1}11] \)

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9

2011 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2011

The magnitude of burgers vector in copper is

A

2.54 Å

B

2.39 Å

C

2.20 Å

D

2.18 Å

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10

2012 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2012

Which one of the following is an equilibrium defect?

A

Vacancies

B

Dislocations

C

Stacking faults

D

Grain boundaries

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11

2012 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2012

A unit dislocation splits into two partial dislocations. The correct combination of the Burgers vectors of the partial dislocations for a given unit dislocation having Burgers vector \( \frac{a}{2} [1 \bar{1} 0] \) is

A

\(\frac{a}{6} [2 \bar{1} \bar{1}] \) and \(\frac{a}{6} [1 \bar{2} 1] \)

B

\(\frac{a}{6} [1 \bar{1} 2] \) and \(\frac{a}{6} [\bar{1} 2 \bar{1}] \)

C

\(\frac{a}{6} [1 \bar{1} 2] \) and \(\frac{a}{6} [2 \bar{1} \bar{1}] \)

D

\(\frac{a}{6} [2 \bar{1} 1] \) and \(\frac{a}{6} [1 \bar{2} \bar{1}] \)

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12

2013 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2013

As the concentration of point defects in a crystal increases, its configurational entropy

A

does not change

B

decreases

C

increases

D

initially increases and then decreases

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13

2013 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2013

Modulus of the Burgers vector (in nm) is

A

0.125

B

0.25

C

0.50

D

0.625

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14

2014 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2014

Dissociation of a dislocation into two partials in an FCC metal is given by the following equation.
\(\frac{a}{2}[1\overline{1}0] \rightarrow \frac{a}{6}[2\overline{1}\overline{1}] + \frac{a}{6}[1\overline{2}1]\)
On which plane do these two partial dislocations lie?

A

\((\overline{1}11)\)

B

(111)

C

\((1\overline{1}1)\)

D

\((11\overline{1})\)

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15

2017 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2017

For a FCC metal, radius of the largest sphere that can fit in the tetrahedral void (in nm) is ______________ (answer up to three decimal places) \n(Given: lattice parameter = 0.401 nm)

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16

2017 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2017

At low temperature, two parallel edge dislocations lying on parallel slip planes are shown in different configurations below.

Match the following:
Configuration [P] [1] Dislocations repel
Configuration [Q] [2] Dislocations attract
Configuration [R] [3] Dislocations are in stable equilibrium
Configuration [S] [4] Dislocations are in unstable equilibrium

A

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

B

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

C

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

D

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

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17

2018 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2018

What is the requirement for equilibrium at a triple junction as shown in the schematic, with \(\gamma_{12}\), \(\gamma_{23}\) and \(\gamma_{13}\) as grain boundary tensions and \(\theta_1\), \(\theta_2\) and \(\theta_3\) as dihedral angles?

A

\(\dfrac{\gamma_{23}}{\cos(\theta_1)} = \dfrac{\gamma_{13}}{\cos(\theta_2)} = \dfrac{\gamma_{12}}{\cos(\theta_3)}\)

B

\(\dfrac{\gamma_{23}}{\sin(\theta_1)} = \dfrac{\gamma_{13}}{\sin(\theta_2)} = \dfrac{\gamma_{12}}{\sin(\theta_3)}\)

C

\(\dfrac{\gamma_{23}}{\sin(\theta_2).\sin(\theta_3)} = \dfrac{\gamma_{13}}{\sin(\theta_1).\sin(\theta_3)} = \dfrac{\gamma_{12}}{\sin(\theta_1).\sin(\theta_2)}\)

D

\(\gamma_{23}\sin(\theta_1) = \gamma_{13}\sin(\theta_2) = \gamma_{12}\sin(\theta_3)\)

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18

2018 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2018

Consider a dilute substitutional solid solution of X in a metal A. The powder diffraction pattern of this alloy reveals that all the peaks have shifted to the left when compared to those for pure A (with no splitting of peaks). If such a solute interacts and segregates to an edge dislocation, which of the following positions around the dislocation will it preferentially occupy?

A

P

B

Q

C

R

D

S

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19

2020 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2020

The number of atoms per unit area in (100) plane of Pb is ______ nm⁻² (round off to the nearest integer).

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20

2020 · Metallurgical Engineering · Physical Metallurgy · Crystal Imperfections

Metallurgical Engineering (MT) 2020

Radius of the largest interstitial atom that can be accommodated in an octahedral void in BCC iron without distorting the lattice is ________ nm (round off to three decimal places).
Assume hard sphere model and radius of Fe atom as 0.124 nm.

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