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Materials Characterisation and Crystal Imperfections(20)Diffusion in Solids(6)Phase Transformation and Solid-state Transformations(9)Principles of Heat Treatment and Corrosion(12)

Materials Characterisation and Crystal Imperfections

20 Questions

GATE→2026→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q1

MCQ[1 Mark]

During metallography, Nital is the most commonly used etchant for (A) Bronze (B) Brass (C) Mild Steel (D) Aluminium

(A)

Bronze

(B)

Brass

(C)

Mild Steel

(D)

Aluminium

Explanation

GATE→2026→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q2

MCQ[1 Mark]

Which one of the following options is correct? In a face-centered cubic metal, a Shockley partial is: (A) Perfect and mobile dislocation (B) Perfect and immobile dislocation (C) Imperfect and immobile dislocation (D) Imperfect and mobile dislocation

(A)

Perfect and mobile dislocation

(B)

Perfect and immobile dislocation

(C)

Imperfect and immobile dislocation

(D)

Imperfect and mobile dislocation

Explanation

GATE→2026→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q3

MCQ[1 Mark]

Residual stress present in a material can be determined by which one of the following techniques: (A) X-ray Diffraction (XRD) (B) Tensile Testing (C) Thermo-Gravimetric Analysis (TGA) (D) Optical Microscopy

(A)

X-ray Diffraction (XRD)

(B)

Tensile Testing

(C)

Thermo-Gravimetric Analysis (TGA)

(D)

Optical Microscopy

Explanation

GATE→2026→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q4

NAT[2 Marks]

A metal having body-centered cubic structure is analyzed through X-ray diffraction using monochromatic X-ray of wavelength $0.154\text{ nm}$. The diffraction angle ($2\theta$) corresponding to $\{200\}$ plane is $60^\circ$. The atomic radius is ___ $\text{nm}$.

Explanation

GATE→2026→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q5

NAT[2 Marks]

The lattice parameter of Ni is $0.35\text{ nm}$ and shear modulus is $76\text{ GPa}$. Strain energy per unit length of screw dislocation is ___ $\times 10^{-9}\text{ J/m}$.

Explanation

GATE→2025→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q6

MCQ[1 Mark]

Match each crystal defect in Column I with the corresponding type in Column II:\nColumn I:\nP. Edge dislocation\nQ. Stacking fault\nR. Frenkel defect\nS. Porosity\nColumn II: 1. Zero-dimensional defect 2. One-dimensional defect 3. Two-dimensional defect 4. Three-dimensional defect (A) P-3, Q-4, R-2, S-1 (B) P-3, Q-4, R-1, S-2 (C) P-2, Q-3, R-1, S-4 (D) P-2, Q-4, R-3, S-1

(A)

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

(B)

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

(C)

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

(D)

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

Explanation

GATE→2025→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q7

MCQ[1 Mark]

In optical microscopy, which one of the following combinations of wavelength ($\lambda$) and numerical aperture (NA) provides the best spatial resolution? (A) $\lambda = 400\text{ nm}$ and $\text{NA} = 1.0$ (B) $\lambda = 600\text{ nm}$ and $\text{NA} = 1.2$ (C) $\lambda = 400\text{ nm}$ and $\text{NA} = 1.2$ (D) $\lambda = 600\text{ nm}$ and $\text{NA} = 1.0$

(A)

\lambda=400 nm and NA=1.0

(B)

\lambda=600 nm and NA=1.2

(C)

\lambda=400 nm and NA=1.2

(D)

\lambda=600 nm and NA=1.0

Explanation

GATE→2025→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q8

MCQ[1 Mark]

The coordination number for an octahedral site in pure copper is _______. (A) 4 (B) 6 (C) 8 (D) 12

(A)

4

(B)

6

(C)

8

(D)

12

Explanation

GATE→2025→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q9

NAT[2 Marks]

X-ray diffraction using a monochromatic radiation of wavelength $0.154\text{ nm}$ is performed on powder samples of metal A (with FCC crystal structure) and metal B (with BCC crystal structure). If the first peak in both the cases occurs at a Bragg angle $\theta = 20^\circ$, then the value of $\frac{\text{lattice parameter of metal A}}{\text{lattice parameter of metal B}}$ is ___ (rounded off to two decimal places).

Explanation

GATE→2025→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q10

NAT[2 Marks]

A single crystal BCC metal with a lattice parameter $a = 0.4\text{ nm}$ is subjected to deformation at a shear strain rate of $0.001\text{ s}^{-1}$. If the average mobile dislocation density in the single crystal is $10^{10}\text{ m}^{-2}$, the average dislocation velocity is ___ $\times 10^{-3}\text{ m s}^{-1}$ (rounded off to two decimal places). Given: Burgers vector $b = \frac{a}{2}\langle 111 \rangle$

Explanation

GATE→2024→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q11

MSQ[1 Mark]

Which of the following $(h\text{ }k\text{ }l)$ reflections is/are allowed in an X-ray diffraction pattern of a crystal with face centered cubic lattice? (A) $(0\text{ }0\text{ }1)$ (B) $(0\text{ }1\text{ }1)$ (C) $(1\text{ }1\text{ }1)$ (D) $(0\text{ }0\text{ }2)$

(A)

(0 0 1)

(B)

(0 1 1)

(C)

(1 1 1)

(D)

(0 0 2)

Explanation

GATE→2024→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q12

MCQ[2 Marks]

Match the entries in Column I with the stacking sequences of the close-packed planes listed in Column II.\nColumn I:\nP. Face centered cubic (FCC) structure\nQ. Intrinsic stacking fault in FCC\nR. Across an annealing twin boundary in FCC\nS. Hexagonal close-packed structure\nColumn II: 1. ABCABABC 2. ABABABAB 3. ABCABCABC 4. ABACABA (A) P-1, Q-3, R-4, S-2 (B) P-2, Q-3, R-1, S-4 (C) P-3, Q-1, R-4, S-2 (D) P-3, Q-2, R-1, S-4

(A)

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

(B)

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

(C)

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

(D)

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

Explanation

GATE→2024→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q13

NAT[2 Marks]

If for element A, the formation enthalpy and formation entropy per vacancy created are $0.5\text{ eV}$ and $3k_B$, respectively, then the equilibrium vacancy concentration (in mole fraction) at $500\text{ K}$ is ___ $\times 10^{-4}$ (Round off to two decimal places).\nGiven: Boltzmann constant $k_B = 8.62 \times 10^{-5}\text{ eV atom}^{-1}\text{K}^{-1}$

Explanation

GATE→2023→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q14

MCQ[1 Mark]

Magnitude of Burgers vector of the dislocation resulting from reaction of dislocations with Burgers vectors $\frac{a}{2}[1\text{ }0\text{ }1]$ and $\frac{a}{2}[0\text{ }\bar{1}\text{ }\bar{1}]$ is (A) $\frac{a}{\sqrt{2}}$ (B) $\sqrt{2}a$ (C) $\frac{a}{2}$ (D) $2a$

(A)

\frac{a}{\sqrt{2}}

(B)

\sqrt{2}a

(C)

\frac{a}{2}

(D)

2 a

Explanation

GATE→2023→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q15

MSQ[1 Mark]

The condition(s) for high degree of mutual substitutional solid solubility for two metals is/are (A) metals should have same valence (B) metals should have same crystal structure (C) the difference in atomic size of metals should be less than 15% (D) the difference in electronegativity of metals should be large

(A)

metals should have same valence

(B)

metals should have same crystal structure

(C)

the difference in atomic size of metals should be less than 15%

(D)

the difference in electronegativity of metals should be large

Explanation

GATE→2023→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q16

MSQ[2 Marks]

A dislocation loop PQRSTU is on the $(1\text{ }1\text{ }1)$ plane of a cubic single crystal with $\frac{1}{6}[\bar{1}\text{ }2\text{ }\bar{1}]$ Burgers vector. The dislocation segments $\vec{PU}$ and $\vec{PQ}$ are parallel to $[0\text{ }1\text{ }1]$ and $[1\text{ }\bar{1}\text{ }0]$ directions, respectively. The correct statement(s) is/are (A) Dislocation segment PQ is mixed in character. (B) Dislocation segment UT is screw in character. (C) Dislocation segment PU is mixed in character. (D) Dislocation segment QR is edge in character.

(A)

Dislocation segment PQ is mixed in character.

(B)

Dislocation segment UT is screw in character.

(C)

Dislocation segment PU is mixed in character.

(D)

Dislocation segment QR is edge in character.

Explanation

GATE→2023→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q17

NAT[2 Marks]

Diffraction pattern of a polycrystalline BCC metal is obtained using monochromatic X-rays of wavelength $0.25\text{ nm}$. If the first peak occurs at Bragg angle ($\theta$) of $30^{\circ}$, then the radius of the metal atom in nm is ___ (round off to 2 decimal places).

Explanation

GATE→2022→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q18

MCQ[1 Mark]

The sequence of peaks corresponding to the planes (in the order of increasing $2\theta$) observed in the X-ray diffractogram of a pure copper powder sample is (A) 111, 200, 220, 311 (B) 110, 200, 211, 220 (C) 110, 200, 211, 311 (D) 111, 200, 311, 220

(A)

111, 200, 220, 311

(B)

110, 200, 211, 220

(C)

110, 200, 211, 311

(D)

111, 200, 311, 220

Explanation

GATE→2022→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q19

MCQ[2 Marks]

Find the correct match between dislocation reactions (Column A) to the descriptions (Column B)\nColumn A: (P) $\frac{a_{o}}{2}[\bar{1}\bar{1}1]+\frac{a_{o}}{2}[111]=a_{o}[001]$ (Q) $\frac{a_{o}}{6}[\bar{1}2\bar{1}]+\frac{a_{o}}{6}[1\bar{1}2]=\frac{a_{o}}{6}[011]$ (R) $\frac{a_{o}}{6}[1\bar{2}1]+\frac{a_{o}}{6}[\bar{1}\bar{1}2]=\frac{a_{o}}{2}[0\bar{1}1]$\nColumn B: (1) Leading partials merging to form a Lomer-Cottrell lock in an FCC metal (2) Energetically unfavorable dislocation reaction in an FCC metal (3) Typical dislocation reaction in a BCC metal (A) P-3, Q-2, R-1 (B) P-3, Q-1, R-2 (C) P-2, Q-3, R-1 (D) P-2, Q-1, R-3

(A)

P-3 Q-2 R-1

(B)

P-3 Q-1 R-2

(C)

P-2 Q-3 R-1

(D)

P-2 Q-1 R-3

Explanation

GATE→2022→Physical Metallurgy→Materials Characterisation and Crystal Imperfections

Q20

NAT[2 Marks]

Consider a tilt boundary of misorientation of $2^{\circ}$ in an aluminium grain. The lattice parameter of aluminium is $0.143\text{ nm}$. The spacing between the dislocations that form the tilt boundary is ___ $\text{nm}$ (round off to 2 decimal places).

Explanation

Diffusion in Solids

6 Questions

GATE→2026→Physical Metallurgy→Diffusion in Solids

Q21

MCQ[1 Mark]

Which one of the following options is correct? In a binary alloy system, during spinodal decomposition, uphill diffusion occurs: (A) From higher to lower concentration and from higher to lower chemical potential (B) From higher to lower concentration and from lower to higher chemical potential (C) From lower to higher concentration and from lower to higher chemical potential (D) From lower to higher concentration and from higher to lower chemical potential

(A)

From higher to lower concentration and from higher to lower chemical potential

(B)

From higher to lower concentration and from lower to higher chemical potential

(C)

From lower to higher concentration and from lower to higher chemical potential

(D)

From lower to higher concentration and from higher to lower chemical potential

Explanation

GATE→2026→Physical Metallurgy→Diffusion in Solids

Q22

NAT[2 Marks]

During carburizing of steel at $950^\circ\text{C}$, the time required to reach $0.8859\text{ wt.}\%$ C at $0.2\text{ mm}$ depth is ___ seconds.

Explanation

GATE→2025→Physical Metallurgy→Diffusion in Solids

Q23

MCQ[2 Marks]

The following are the activation energies for diffusion of carbon and iron at $773\text{ K}$ in polycrystalline BCC iron: $P =$ Activation energy for diffusion of carbon in BCC iron through the lattice $Q =$ Activation energy for diffusion of iron in BCC iron through the lattice $R =$ Activation energy for diffusion of iron in BCC iron along the grain boundary\nWhich one of the following statements is CORRECT? (A) $R < P < Q$ (B) $R < Q < P$ (C) $Q < P < R$ (D) $P < R < Q$

(A)

R < P < Q

(B)

R < Q < P

(C)

Q < P < R

(D)

P < R < Q

Explanation

GATE→2024→Physical Metallurgy→Diffusion in Solids

Q24

NAT[2 Marks]

During carburization of a steel at $950^\circ\text{C}$, carbon concentration is measured as $0.8\text{ wt.}\%$ at a depth of $0.3\text{ mm}$ after one hour. The time required to get the same carbon concentration at a depth of $0.6\text{ mm}$ at the same carburization temperature is ___ hours (Round off to the nearest integer).

Explanation

GATE→2023→Physical Metallurgy→Diffusion in Solids

Q25

MCQ[1 Mark]

For self-diffusion in polycrystalline copper with a lattice diffusion coefficient $D_{L}$, grain boundary diffusion coefficient $D_{GB}$, and surface diffusion coefficient $D_{S}$, the correct relationship is (A) $D_{S} > D_{GB} > D_{L}$ (B) $D_{L} > D_{S} > D_{GB}$ (C) $D_{GB} > D_{S} > D_{L}$ (D) $D_{GB} = D_{S} = D_{L}$

(A)

D_{S}>D_{GB}>D_{L}

(B)

D_{L}>D_{S}>D_{GB}

(C)

D_{GB}>D_{S}>D_{L}

(D)

D_{GB}=D_{S}=D_{L}

Explanation

GATE→2022→Physical Metallurgy→Diffusion in Solids

Q26

NAT[2 Marks]

The concentration $C$ of a solute (in units of atoms-mm$^{-3}$) in a solid along $x$ direction (for $x>0$) follows the expression $$C = a_1 x^2 + a_2 x$$\nwhere $x$ is in $\text{mm}$, $a_1$ and $a_2$ are in units of atoms-mm$^{-4}$ and atoms-mm$^{-3}$, respectively. Assuming $a_1 = a_2 = 1$, the magnitude of flux at $x = 2\text{ mm}$ is ___ $\times 10^{-3}\text{ atoms-mm}^{-2}\cdot\text{s}^{-1}$ (answer rounded off to the nearest integer).\nGiven: diffusion coefficient of the solute in the solid is $3 \times 10^{-3}\text{ mm}^2\cdot\text{s}^{-1}$.

Explanation

Phase Transformation and Solid-state Transformations

9 Questions

GATE→2026→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q27

MCQ[1 Mark]

Which one of the following options is correct? In Al - 4 wt.% Cu alloy during isothermal aging, the correct precipitation sequence is: (A) $\theta'' \rightarrow \theta' \rightarrow \theta \rightarrow \text{GP zone}$ (B) $\text{GP zone} \rightarrow \theta \rightarrow \theta' \rightarrow \theta''$ (C) $\theta \theta' \theta'' \rightarrow \text{GP zone}$ (D) $\text{GP zone} \rightarrow \theta'' \rightarrow \theta' \rightarrow \theta$

(A)

\Theta^{\prime\prime}\rightarrow\theta^{\prime}\rightarrow\theta\rightarrow GP zone

(B)

GP zone \rightarrow\theta\rightarrow\theta^{\prime}\rightarrow\theta^{\prime\prime}

(C)

00'0" \rightarrow GP zone

(D)

GP zone \rightarrow\theta^{\prime\prime}\rightarrow\theta^{\prime}\rightarrow\theta

Explanation

GATE→2026→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q28

NAT[2 Marks]

An alloy having composition W-20 wt.% Ni is prepared by mixing elemental powders. The resulting powder mixture is liquid phase sintered at $1550^\circ\text{C}$ for 1 hour. The tungsten grain size is $70\text{ }\mu\text{m}$ and neck diameter is $35\text{ }\mu\text{m}$. If W-Ni interfacial energy is $0.30\text{ J/m}^2$, W-W interfacial energy is ___ $\text{J/m}^2$.

Explanation

GATE→2026→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q29

NAT[2 Marks]

For homogeneous nucleation with $\Delta G_v = -0.5 \times 10^8\text{ J/m}^3$ and $\gamma = 0.1\text{ J/m}^2$, the critical nucleus size is ___ $\text{nm}$.

Explanation

GATE→2025→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q30

MCQ[1 Mark]

In the Fe-C system, the invariant reaction $\text{Liquid} + \delta \rightleftharpoons \gamma$ takes place at $1493^\circ\text{C}$. This type of reaction is called _______. (A) eutectic (B) eutectoid (C) peritectic (D) monotectic

(A)

eutectic

(B)

eutectoid

(C)

peritectic

(D)

monotectic

Explanation

GATE→2025→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q31

MSQ[1 Mark]

Which of the following statements is/are CORRECT with respect to the initial stage of GP zone formation in a precipitation hardenable Al - 4.5 wt.% Cu alloy? (A) GP zones are Cu-rich clusters. (B) GP zones are CuAl$_2$ precipitates. (C) GP zones are incoherent with the matrix. (D) GP zones are coherent with the matrix.

(A)

GP zones are Cu-rich clusters.

(B)

GP zones are CuAl2 precipitates.

(C)

GP zones are incoherent with the matrix.

(D)

GP zones are coherent with the matrix.

Explanation

GATE→2024→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q32

MCQ[1 Mark]

Which one of the following schematics represents the variation of the rate of nucleation of solid from a pure liquid metal as a function of undercooling ($\Delta T = T_m - T$)?

(A)

Option A

(B)

Option B

(C)

Option C

(D)

Option D

Explanation

GATE→2024→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q33

NAT[1 Mark]

For a solid embryo in contact with a perfectly flat mould wall as shown in the schematic, the wetting angle $\theta$ is ___ degrees (Round off to one decimal place).\nGiven: Surface tension between liquid and mould wall $= 0.35\text{ J m}^{-2}$, surface tension between solid and mould wall $= 0.02\text{ J m}^{-2}$, surface tension between liquid and solid $= 0.30\text{ J m}^{-2}$

Explanation

GATE→2024→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q34

MCQ[2 Marks]

The constitutional undercooling condition for a hypothetical binary alloy of A with solute B during solidification is shown in the figure along with its binary phase diagram. Based on these two schematics, one can conclude that the solute concentration in region X will be _______ the average composition of the initial liquid phase. (A) less than (B) greater than (C) same as (D) independent of

(A)

less than

(B)

greater than

(C)

same as

(D)

independent of

Explanation

GATE→2022→Physical Metallurgy→Phase Transformation and Solid-state Transformations

Q35

NAT[2 Marks]

During solidification of a pure metal, the radius of critical nucleus at an undercooling of $10\text{ K}$ is ___ $\times 10^{-9}\text{ m}$ (answer rounded off to 1 decimal place).\nGiven: solid/liquid interface energy $= 0.177\text{ J}\cdot\text{m}^{-2}$, melting point of the metal $= 1356\text{ K}$, and latent heat of fusion $= 1.88\text{ }\times 10^{9}\text{ J}\cdot\text{m}^{-3}$.

Explanation

Principles of Heat Treatment and Corrosion

12 Questions

GATE→2026→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q36

MCQ[1 Mark]

Which one of the following options is correct? For Al - 4% Ag alloy (composition in atom %), the correct sequence of operations involved in precipitation hardening is: (A) Quenching $\rightarrow$ Aging $\rightarrow$ Solution treatment (B) Solution treatment $\rightarrow$ Aging $\rightarrow$ Quenching (C) Aging $\rightarrow$ Solution treatment $\rightarrow$ Quenching (D) Solution treatment $\rightarrow$ Quenching $\rightarrow$ Aging

(A)

Quenching \rightarrow Aging \rightarrow Solution treatment

(B)

Solution treatment \rightarrow Aging \rightarrow Quenching

(C)

Aging \rightarrow Solution treatment \rightarrow Quenching

(D)

Solution treatment \rightarrow Quenching \rightarrow Aging

Explanation

GATE→2026→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q37

MCQ[1 Mark]

Which one of the following options is correct? After cold-working of a metallic specimen, during the recovery stage, its electrical conductivity: (A) Always increases (B) Always decreases (C) Can increase or decrease (D) Remains unaffected

(A)

Always increases

(B)

Always decreases

(C)

Can increase or decrease

(D)

Remains unaffected

Explanation

GATE→2026→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q38

MSQ[1 Mark]

Which of the following elements, when present in iron, enhance(s) its corrosion resistance? (A) H (B) Cr (C) S (D) C

(A)

H

(B)

Cr

(C)

S

(D)

C

Explanation

GATE→2025→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q39

MSQ[2 Marks]

Which of the following statements is/are CORRECT when Ni is added as an alloying element to a low alloy steel? (A) Hardenability is increased AND the $M_s$ temperature is lowered. (B) Hardenability is decreased AND the $M_s$ temperature is lowered. (C) Hardenability is increased AND the $M_s$ temperature is raised. (D) Hardenability is decreased AND the $M_s$ temperature is raised.

(A)

Hardenability is increased AND the Ms temperature is lowered.

(B)

Hardenability is decreased AND the Ms temperature is lowered.

(C)

Hardenability is increased AND the Ms temperature is raised.

(D)

Hardenability is decreased AND the Ms temperature is raised.

Explanation

GATE→2024→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q40

MCQ[1 Mark]

Which one of the following crystal structure changes occurs during the transformation of mild steel from austenite to martensite? (A) Face centered cubic to body centered cubic (B) Face centered cubic to body centered tetragonal (C) Body centered cubic to body centered tetragonal (D) Body centered tetragonal to face centered cubic

(A)

Face centered cubic to body centered cubic

(B)

Face centered cubic to body centered tetragonal

(C)

Body centered cubic to body centered tetragonal

(D)

Body centered tetragonal to face centered cubic

Explanation

GATE→2024→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q41

MCQ[2 Marks]

The microstructures of a quenched steel tempered at three temperatures $T_1 < T_2 < T_3$ for a fixed time are schematically illustrated with average radii $\bar{r}_1 < \bar{r}_2 < \bar{r}_3$ and volume fractions $V_1 < V_2 = V_3$. If cementite is more noble than ferrite, which microstructure has the highest corrosion rate in 3.5 wt.% NaCl? (A) Microstructure at $T_1$ (B) Microstructure at $T_3$ (C) Microstructure at $T_2$ (D) All have equal corrosion rate

(A)

Microstructure at T_{1}

(B)

Microstructure at T_{3}

(C)

Microstructure at T_{2}

(D)

All have equal corrosion rate

Explanation

GATE→2024→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q42

NAT[2 Marks]

A mild steel pipeline is connected to zinc for cathodic protection at a current density of $10\text{ mA m}^{-2}$. The quantity of zinc required per square meter of the pipeline per year is ___ grams (Round off to the nearest integer).\nGiven: Atomic weight of Zn is $65\text{ g mol}^{-1}$, Faraday's constant $F = 96500\text{ C mol}^{-1}$.

Explanation

GATE→2023→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q43

MSQ[2 Marks]

For the given schematic TTT diagram of an eutectoid steel, the following statement(s) is/are true for the heat treatment schedules HT-1, HT-2, and HT-3. (A) HT-3 leads to the formation of a pearlite microstructure (B) HT-1 leads to a predominantly martensite microstructure (C) HT-2 leads to a bainite microstructure (D) HT-3 leads to a mixture of pearlite and bainite microstructure

(A)

HT-3 leads to the formation of a pearlite microstructure

(B)

HT-1 leads to a predominantly martensite microstructure

(C)

HT-2 leads to a bainite microstructure

(D)

HT-3 leads to a mixture of pearlite and bainite microstructure

Explanation

GATE→2023→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q44

MSQ[2 Marks]

Choose the correct statement(s) in the context of fusion welding of austenitic stainless steel containing about $0.06\text{ wt.}\%$ carbon. (A) Corrosion resistance of heat affected zone is poorer than base material. (B) Corrosion resistance of heat affected zone is superior than fusion zone. (C) Corrosion resistance of heat affected zone is same as fusion zone. (D) Corrosion resistance is same for fusion zone, heat affected zone, and base material.

(A)

Corrosion resistance of heat affected zone is poorer than base material.

(B)

Corrosion resistance of heat affected zone is superior than fusion zone.

(C)

Corrosion resistance of heat affected zone is same as fusion zone.

(D)

Corrosion resistance is same for fusion zone, heat affected zone, and base material.

Explanation

GATE→2022→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q45

MCQ[1 Mark]

The CCT diagram of a eutectoid steel with a superimposed cooling curve is shown in the figure. The microstructure at room temperature (RT) after this heat treatment is (A) pearlite only (B) pearlite + retained austenite (C) martensite only (D) pearlite + martensite

(A)

pearlite only

(B)

pearlite + retained austenite

(C)

martensite only

(D)

pearlite + martensite

Explanation

GATE→2022→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q46

MCQ[1 Mark]

With increase in carbon content (up to 2 mass%) in Fe-C alloy, which one of the following statements is correct with respect to the lattice parameters ($c$ and $a$) of BCT martensite? (A) Both $c$ and $a$ increase (B) $c$ increases but $a$ decreases (C) $c$ decreases but $a$ increases (D) Both $c$ and $a$ decrease

(A)

Both c and a increase

(B)

c increases but a decreases

(C)

c decreases but a increases

(D)

Both c and a decrease

Explanation

GATE→2022→Physical Metallurgy→Principles of Heat Treatment and Corrosion

Q47

MSQ[1 Mark]

Identify the correct statement(s) with respect to the role of nickel as an alloying element in steels. (A) It increases the $M_s$ temperature (B) It is an austenite stabiliser (C) It decreases the $M_s$ temperature (D) It is a carbide former

(A)

It increases the M_{s} temperature

(B)

It is an austenite stabiliser

(C)

It decreases the M_{s} temperature

(D)

It is a carbide former

Explanation