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1Introduction
z Part of phase diagram :z Components (solute,
solvent)z Compositionz Temperaturez Systemz Phasez Solubility
limit
z Phase : a homogeneous portion of a system that has homogeneous
chemical and physical properties
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2Isomorphous Cu-Ni
Lever Arm Rule
z Applied in the two phases region
z Will be used to obtain the relative amount of phases
present
z The total amount shall be 100%
z Example is Alloy B (Co % Ni), at 1250 oC
z Two phases are present : and Liquid
z The amount of liquid :
z The amount of :
L
oL CC
CCSR
SW =+=
L
Lo
CCCC
SRRW
=+=
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3Binary Eutectic System
+LactionEutectic :Re
Peritectic reaction : Eutectoid reaction :
+ L +
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4Iron Carbide Phase Diagram
0.10 0.50
0.18
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5Phases and Compound
z (ferrite) :z Pure iron, when C = 0z BCCz Magneticz Stable up
to 912 oCz Max solubility of C = 0.022%
z (austenite) :z FCCz Non-magneticz Max solubility of C =
2.14%
z (delta) :z BCCz Magneticz Stable at high temperature
z Fe3C (cementite) :z Compoundz Occurred at 6.70% C
z Peritectic reaction :z At T = 1493 oCz + L
z Eutectic reactionz At T = 1147 oCz L + Fe3C
z Eutectoid reactionz At T = 723 oCz + Fe3C (Pearlite)
400 X
200 X
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6Hypoeutectoid Steel
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7Hypereutectoid Steel
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8
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9
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10
Weight % and Atom %
z Weight (or mass) percent :
z Atom percent :
10021
11 Xmm
mC +=1
11 A
mnm =
10021
1'1 Xnn
nCmm
m
+=
Conversion of Weight % to Atom %
z Weight % (C1, C2) to Atom % (C1, C2):
z Atom % (C1, C2) to Weight % (C1, C2) :
1001221
21'1 XACAC
ACC +=
1001221
12'2 XACAC
ACC +=
1002
'21
'1
1'1
1 XACACACC +=
1002
'21
'1
2'2
2 XACACACC +=
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11
Conversion of Weight % to Weight/Volume
z Weight % (C1, C2) to Weight/Volume (C1, C2) :
3
2
2
1
1
1"1 10XCC
CC
+=
3
2
2
1
1
2"2 10XCC
CC
+=
Density and Atomic Weight of Binary Alloys
z Density : z Atomic Weight :
+
=2
2
1
1
100
CCavg
+
+=2
2'2
1
1'1
2'21
'1
ACACACAC
avg
+
=2
2
1
1
100
AC
AC
Aavg
1002
'21
'1 ACACAavg
+=
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12
Calculation Example
z Determine the composition in atom percent of an alloy that
consists of 97 wt.% aluminum and 3 wt.% copper. AAl = 26.98 g/mol,
ACu = 63.55 g/mol.
100' XACAC
ACCAlCuCuAl
CuAlAl +=
.%7.98100)98.26()3()55.63()97(
)55.63()97(' atXCAl =+=
.%30.1100)98.26()3()55.63()97(
)98.26()3(' atXCCu =+=
