yncug vacUlurcen-gnireen gn aFcallucaF
1st year Mining, Petroleum and Metallurgical Engineering,
Materials Science
mcx elui dni 2008 ecil :5 1 h
Name : -----Dr. Mahmoud M.Tash (Model Answer)---------B.N.-----------------Question One:
Sketch BCC and FCC unit cells.
Q1: Answer- Sketch of FCC
Q1: Answer- Sketch of BCC
2. Sketch the arrangement of the lattice
points on a {111} type plane in a FCC
and the same for a {110} type plane
in a BCC lattice.
Q2: Answer- Sketch of (111)
Q1: Answer- Sketch of (110)
1.
Plane (111)
Plane (110)
Iron has a density of 7.87 gm/cm3 [At. Wt. of Fe=55.85, A.N.= 0.6002x10 24]. The atomic radius is ------------a) r=2.24
Å b) r=3.24 Å c) r=1.24 Å d) r=0.24 Å
4. Iron has a lattice parameter of 0.2866 nm [At. Wt. of Fe=55.85, A.N.= 0.6002x10 24] . The Density of iron is------------a) 7.882 gm/cm3
b) 7.1 gm/cm3
c) 9 gm/cm3
d) 6 gm/cm3
5. Number of atoms per unit cell in BCC is -------- a) 2 b) 4
c) 6
d) 8
6. Number of atoms per unit cell in FCC is -------- a) 2 b) 4
c) 6
d) 8
7. Relationship between the lattice constant and the atomic radius in BCC is ------- a) r=a*√3
b) 4*r= a*√2
c) 4*r= a*2
d) 4*r=a*√3
8. Relationship between the lattice constant and the atomic radius in FCC is -------- a) r= a*√2
b) 4*r= a*√2
c) 4*r= a*2
d) 4*r=a*√3
9. Atomic packing factor in BCC a) 0.2
b) 0.74
c) 0.68
d) 0.8
10. Atomic packing factor in FCC a) 0.2
b) 0.74
c) 0.68
d) 0.8
3.
11. In Figure 1 below, Plane A is -----a) (210)
b) (110)
c) (111)
d) (01-0)
12. In Figure 1 below, Plane B is -----a) (210)
b) (110)
c) (111)
d) (01-0)
13. In Figure 1 below, Plane C is -----a) (210)
b) (110)
c) (111)
d) (01-0)
Figure 1
14. The atomic radius of BCC tungsten is 1.4 Å [At. wt = 183.8 g/g.mole, A.N.= 0.6002x1024]. The density of tungsten is ------------------ a) 14 gm/cm3
b) 18.3 gm/cm3
c) 9 gm/cm3
d) 16 gm/cm3
15. The basic types of imperfections are a) point defects
b) line defects (or dislocations), c) surface defects)
d) all of the above
16. Metals have -----low-------melting point (Tm) and ---------low---------------------- modul’s of elasticity (E) while ceramics
have ------high----------- melting point (Tm) and -----------high------------- modul’s of elasticity (E)
Answer for Question One:
1
------ 2
-----9
c
10
b
3
11
c
c
4
12
a
a
5
13
1
a
d
6
14
b
b
7
15
d
d
8
16
B
------
yncug vacUlurcen-gnireen gn aFcallucaF
1st year Mining, Petroleum and Metallurgical Engineering,
Materials Science
mcx elui dni 2008 ecil :5 1 h
Question Two:
1. The eutectoid steel in Fe-C diagram has an austenite phase of composition ….. just below 1140C. (a) 4.3%C (b) 0.8%C
(c) 2%C (d) 0.02%C.
2. The eutectic alloy on the Fe-Fe3C Diagram contains (a) 4.3%C (b) 0.8%C (c) 2%C (d) 0.02%C.
3. The 0.5%C steel contains less than 0.02%C in it’s ………. At 750ºC. (a) Austenite (b) Pearlite (c) Ferrite (d) Cementite
4. The amount of phases of alloy contains 0.2% C after equilibrium cooling to room temperature is:- (a) 90% ferrite+ 10%
austenite
(b) 97% ferrite + 3%austenite (c) 97% ferrite + 3% Fe3C
(d) 97% Fe3C + 3% ferrite
5. The microstructure of hypo-eutectoid steel containing 0.2%C consists of :- (a) 90% pearlite and 10% ferrite (b) 75%
Pearlite and 25% ferrite (c) 75% ferrite and 25% pearlite (d) 100% ferrite At room temperature
6. The number of phases present in an alloy containing 0.4 % carbon, after equilibrium cooling to room temperature are:(a)
2 phases called ferrite and cementite (b) 2 phases called ferrite and pearlite (c) 2 phases called ferrite and austenite (d)
None of the above
7. The amount of phases present in the alloy contains 0.4%C after equilibrium cooling to room temperature is :- (a) 94%
martensite & 6% ferrite (b)94% ferrite& 6% Fe3C (c)94% austenite & 6% ferrite (d)94% Fe3C & 6% ferrite
8. The amount of phases of alloy contains 0.8% C after equilibrium cooling to room temperature is:- (a)88% austenite +
12%ferrite
(b) 60% ferrite + 40%Fe 3C (c) 88% Fe3C + 12% ferrite
(d) 88% ferrite + 12% Fe3C
9. The structure of the alloy containing 0.8%C at 750 0 C consists of :- (a)100% Ferrite (b) 100% Austenite (c) 50% Ferrite
+ 50% Austenite
(d) 100% Pearlite
10. The amount of phases present in the alloy contains 1.2%C after equilibrium cooling to room temperature is :- (a) 94%
martensite & 6% ferrite (b) 82% ferrite& 18% Fe3C (c) 80% austenite & 20% ferrite
(d) 82 Fe 3C & 18% ferrite
Answer for Question Two:
1
c
2
a
3
c
4
c
5
c
6
a
7
b
8
d
9
b
10
B
Question Three:
Sketch the cooling curve and microstructure for eutectoid and eutectic alloys. (N.B. You can answer on the Fe-Fe3C phase
Diagram)
relieci ceegn
L
L--γ+Fe3C
γ+Fe3C
γ--P (ɑ+Fe3C)
P (ɑ+Fe3C)
+ Fe3C
This lamellar structure could be Pearlite (ɑ + Fe3C) in eutectoid steel at RT and eutectic (γ + Fe3C) in eutectic steel
Γ
Pearlite (ɑ + Fe3C)
eutectic (γ + Fe3C)
eutectoid (ɑ + Fe3C) + Fe3C
Good Luck/ Dr. Mahmoud M. Tash
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