• C o < 2 wt% Sn • Result: --at extreme ends --polycrystal of grains i.e., only one solid phase. Microstructures in Eutectic Systems: I 0 L + 200 T(°C) C o , wt% Sn 10 2 20 C o 300 100 L 30 + 400 (room T solubility limit) T E (Pb-Sn System) L L: C o wt% Sn : C o wt% Sn
Microstructures in Eutectic Systems: I
Jan 13, 2016
Microstructures in Eutectic Systems: I. T (°C). L: C o wt% Sn. 400. L. a. L. 300. L. a. +. a. 200. (Pb-Sn. a : C o wt% Sn. T E. System). 100. b. +. a. 0. 10. 20. 30. C o. ,. wt% Sn. C o. 2. (room T solubility limit). • C o < 2 wt% Sn • Result: - PowerPoint PPT Presentation
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• Co < 2 wt% Sn• Result: --at extreme ends --polycrystal of grains i.e., only one solid phase.
Microstructures in Eutectic Systems: I
0
L+ 200
T(°C)
Co, wt% Sn10
2
20Co
300
100
L
30
+
400
(room T solubility limit)
TE
(Pb-SnSystem)
L
L: Co wt% Sn
: Co wt% Sn
• 2 wt% Sn < Co < 18.3 wt% Sn• Result:
Initially liquid + then alonefinally two phases
polycrystal fine -phase inclusions
Microstructures in Eutectic Systems: II
Pb-Snsystem
L +
200
T(°C)
Co , wt% Sn10
18.3
200Co
300
100
L
30
+
400
(sol. limit at TE)
TE
2(sol. limit at Troom)
L
L: Co wt% Sn
: Co wt% Sn
• Co = CE • Result: Eutectic microstructure (lamellar structure) --alternating layers (lamellae) of and crystals.
Microstructures in Eutectic Systems: III
Adapted from Fig. 9.14, Callister 7e.
160 m
Micrograph of Pb-Sn eutectic microstructure
Pb-Snsystem
L
200
T(°C)
C, wt% Sn
20 60 80 1000
300
100
L
L+ 183°C
40
TE
18.3
: 18.3 wt%Sn
97.8
: 97.8 wt% Sn
CE61.9
L: Co wt% Sn
• 18.3 wt% Sn < Co < 61.9 wt% Sn• Result: crystals and a eutectic microstructure
Microstructures in Eutectic Systems: IV
18.3 61.9
SR
97.8
SR
primary eutectic
eutectic
Pb-Snsystem
L+200
T(°C)
Co, wt% Sn
20 60 80 1000
300
100
L
L+
40
+
TE
L: Co wt% Sn LL
L+L+
+
200
Co, wt% Sn20 60 80 1000
300
100
L
TE
40
(Pb-Sn System)
Hypoeutectic & Hypereutectic
160 m
eutectic micro-constituent
hypereutectic: (illustration only)
175 m
hypoeutectic: Co = 50 wt% Sn
T(°C)
61.9eutectic
eutectic: Co = 61.9 wt% Sn
Intermetallic Compounds
Note: intermetallic compound forms a line - not an area - because stoichiometry (i.e. composition) is exact.
Mg2Pb
Cu-Zn Phase diagram
Iron-Carbon Phase Diagram Extract
Fe 3
C (
cem
entit
e)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
(austenite)
+L
+Fe3C
+Fe3C
+
L+Fe3C
(Fe) Co, wt% C
1148°C
T(°C)
727°C = Teutectoid
A
SR
4.300.76
Ceu
tect
oid
B
Pearlite
Fe3C (cementite-hard)
(ferrite-soft)
Result: Pearlite = alternating layers of and Fe3C phases
120 m
Hypoeutectoid Steel
Fe 3
C (
cem
entit
e)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
(austenite)
+L
+ Fe3C
+ Fe3C
L+Fe3C
(Fe) Co , wt% C
1148°C
T(°C)
727°C
(Fe-C System)
C0
0.76
Hypoeutectoid Steel
Proeutectoidferrite
pearlite
100 m
w =S/(R+S)wFe3C =(1-w)
wpearlite = wpearlite
Hypereutectoid Steel
Fe 3
C (
cem
entit
e)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
(austenite)
+L
+Fe3C
+Fe3C
L+Fe3C
(Fe) Co , wt%C
1148°C
T(°C)
(Fe-C System)
0.7
6
Co
Hypereutectoid Steel
proeutectoid Fe3C
60 m
pearlite
w =S/(R+S)wFe3C =(1-w)
wpearlite = wpearlite
Alloying Steel with More Elements
• Teutectoid changes:
TE
ute
cto
id (
°C)
wt. % of alloying elements
Ti
Ni
MoSi
W
Cr
Mn
• Ceutectoid changes:
wt. % of alloying elements
Ce
ute
cto
id (
wt%
C)
Ni
Ti
Cr
SiMn
WMo
Taxonomy of MetalsMetal Alloys
Ferrous Nonferrous
Cu Al Mg TiSteels<1.4 wt% C
Cast Irons3-4.5 wt% C
Fe3C
cementite
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
austenite
+L
+Fe3Cferrite
+Fe3C
+
L+Fe3C
(Fe) Co , wt% C
Eutectic:
Eutectoid:0.76
4.30
727°C
1148°C
T(°C) microstructure: ferrite, graphite cementite
Steels
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