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Match the heat treatment for an eutectoid steel shown in the TTT diagram below (as P, Q, R and S) with the resulting microstructure listed below:<br>1. Fine pearlite<br>2. martensite<br>3. Bainite<br>4. Coarse pearlite<br><img src="/images/question-image/metallurgical-engineering/physical-metallurgy/1684341810-M2-B-7-134.PNG" title="Physical Metallurgy mcq question image" alt="Physical Metallurgy mcq question image">
A
P-1, Q-2, R-4, S-3
B
P-4, Q-1, R-3, S-2
C
P-2, Q-1, R-3, S-4
D
P-1, Q-4, R-3. S-2
Correct Answer:
P-4, Q-1, R-3, S-2
Which of the following cooling curves (shown in schematic) in an eutectoid steel will produce 50% bainitic structure?
A
P
B
Q
C
R
D
S
A simplified energy band-diagram of an intrinsic semiconductor at thermal equilibrium (300 K) is shown. In the accompanying table, which one of the four cloumns correctly represents the listed parameters? Assume same effective mass for electrons and holes.
A
<table class="table-style-1"> <tr> <td rowspan="2">Parameter</td> <td colspan="4">Energy-difference</td> </tr> <tr> <td><strong>Column 1</strong></td> <td><strong>Column 2</strong></td> <td><strong>Column 3</strong></td> <td><strong>Column 4</strong></td> </tr> <tr> <td>Band-gap</td> <td>ΔE<sub>2</sub></td> <td>ΔE<sub>1</sub></td> <td>ΔE<sub>2</sub></td> <td>ΔE<sub>1</sub></td> </tr> <tr> <td>Electron affinity</td> <td>$$\frac{{\Delta {E_1}}}{2}$$</td> <td>ΔE<sub>2</sub> - ΔE<sub>1</sub></td> <td>$$\frac{{\Delta {E_2}}}{2}$$</td> <td>ΔE<sub>2</sub> - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> </tr> <tr> <td>Work function</td> <td>ΔE<sub>1</sub> + ΔE<sub>2</sub></td> <td>ΔE<sub>2</sub> - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> <td>ΔE<sub>1</sub> - $$\frac{{\Delta {E_2}}}{2}$$</td> <td>ΔE<sub>2</sub> + $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> </tr></table> Column 1
B
Column 2
C
Column 3
D
Column 4
An alloy of overall composition, X
B
= 0.7 was equilibrated at temperature T
1
. Microstructural analysis showed two phases, (α and β, and that the phase fraction of β was 0.75. Given that the equilibrium composition of β at Ti is 0.9 as shown in the phase diagram below, the maximum solubility of B in α (in mole fraction) at this temperature is . . . . . . . .
A
0.05
B
0.10
C
0.50
D
0.85
The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10
-11
m
-2
s
-1
. Assume the diffusion couple to be infinitely long.
Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$
A
c<sub>1</sub> = 0.45, c<sub>2</sub> = 0.05
B
c<sub>1</sub> = 0.5, c<sub>2</sub> = 0.4
C
c<sub>1</sub> = -0.05, c<sub>2</sub> = 0.45
D
c<sub>1</sub> = 0.1, c<sub>2</sub> = 0.9
A binary phase diagram of components P and Q displays an eutectoid reaction with terminal solid solutions a on the P rich side and β on the Q rich side. At the eutectoid temperature, the solubilities of Q in a and β are 5 and 90 wt% respectively. The densities of α and β phases are 9.5 and 2.49 gm/cm
3
respectively.
At the eutectoid point, the alloy has α and β in the weight ratio 1 : 1. The eutectoid point occurs at composition . . . . . . . . wt % Q.
A
46
B
47.5
C
50
D
52.5
A furnace wall consists of four layers of different materials, M
1
, M
2
, M
3
and M
4
. If the layers are of equal thickness and the steady state temperature profiles is as shown below, then the material with the lowest thermal conductivity is
A
M<sub>1</sub>
B
M<sub>2</sub>
C
M<sub>3</sub>
D
M<sub>4</sub>
A square of 9 mm
2
area is subjected to simple shear displacement √3 mm along x-direction, as shown below: The strain imparted will be
A
$$\frac{1}{3}$$
B
$$\frac{1}{{\surd 3}}$$
C
$${\surd 3}$$
D
3
A furnace wall is made of three materials (I, II and III) of equal thickness and having thermal conductivity k
1
k
2
and k
3
respectively. The steady state temperature profile inside each material is shown in the figure. Thermal conductivities of the materials will vary as
A
k<sub>1</sub> > k<sub>2</sub> > k<sub>3</sub>
B
k<sub>2</sub> > k<sub>1</sub> > k<sub>3</sub>
C
k<sub>3</sub> > k<sub>1</sub> > k<sub>2</sub>
D
k<sub>3</sub> > k<sub>2</sub> > k<sub>1</sub>
In the hypothetical phase diagram, the melting point of each pure component is. 1000 K and the eutectic temperature is 800 K. The eutectic is located at the equi-atomic composition. The maximum solid solubility in α-phase is given by the mole fraction, Ne = 0.1.
The freezing range (in K) of the alloy with composition, Ne = 0.1 is
A
100
B
130
C
160
D
190
From a 2 m × 1.2m sheet, squares are Cut out from each of the four comers as shown in the figure and then the sides are bent to form an open box. The maximum possible volume (in m
3
) of the box is
A
0.14
B
0.26
C
0.54
D
0.82
