" Correlation of the Eutectic Type Alloy with the Phase Diagram " s96aif@gmail.com

1. Baghdad University
College of Engineering
Department of Mechanical Engineering
Name of Experiment
" Correlation of the Eutectic Type Alloy with the Phase Diagram "
Preparation:
Saif al-Din Ali Madi
The second phase
Group "A "

2. 1. Name of Experiment Correlation of the Eutectic Type Alloy
with the Phase Diagram
2. The Objective of the Experiment: To study a binary Eutectic
alloy and correlating it with its phase diagram
3. Devices Used for Experiment
a. Specimens of Sn-Pb of different concentrations Microscope
4. Theory should contain the following
a. How are they drawn?
BINARY EUTECTIC SYSTEMS
We will take an example and explain the whole spectrum to him

3. The copper-silver phase diagram 1
(for the a phase), and similarly for copper in silver (for the b phase). The solubility
limit for the a phase corresponds to the boundary line, labeled CBA, between the
a/(a + b) and a/(a + L) phase regions; it increases with temperature to a maximum
[8.0 wt% Ag at 779C (1434F)] at point B, and decreases back to zero at the melting
temperature of pure copper, point A [1085C (1985F)]. At temperatures below
779C (1434F), the solid solubility limit line separating the a and a b phase regions is
termed a solvus line; the boundary AB between the a and a L fields is the
solidus line, as indicated in Figure. For the b phase, both solvus and solidus lines
also exist, HG and GF, respectively, as shown. The maximum solubility of copper
in the b phase, point G (8.8 wt% Cu), also occurs at 779C (1434F). This horizontal line
BEG, which is parallel to the composition axis and extends between these
maximum solubility positions, may also be considered a solidus line; it represents
the lowest temperature at which a liquid phase may exist for any copper–silver alloy
that is at equilibrium.
There are also three two-phase regions found for the copper–silver system
(Figure 1): a + L, b + L, and a + b. The a- and b-phase solid solutions coexist for
all compositions and temperatures within the a + b phase field; the a + liquid and b +
liquid phases also coexist in their respective phase regions. Furthermore,
compositions and relative amounts for the phases may be determined using tie lines
and the
lever rule as outlined previously.

4. As silver is added to copper, the temperature at which the alloys become
totally liquid decreases along the liquidus line, line AE; thus, the melting
temperature of copper is lowered by silver additions. The same may be said for
silver:
the introduction of copper reduces the temperature of complete melting along
the other liquidus line, FE. These liquidus lines meet at the point E on the phase
diagram, which point is designated by composition CE and temperature TE; for the
copper–silver system, the values for these two parameters are 71.9 wt% Ag and
779C (1434F), respectively. It should also be noted there is a horizontal isotherm
at 779C and represented by the line labeled BEG that also passes through point E.
An important reaction occurs for an alloy of composition CE as it changes
temperature in passing through TE; this reaction may be written as follows:
In other words, upon cooling, a liquid phase is transformed into the two
solid a and b phases at the temperature TE; the opposite reaction occurs
upon heating. This is called a eutectic reaction (eutectic means “easily
melted”), and CE and TE represent the eutectic composition and
temperature, respectively; CaE and CbE are the respective compositions
of the a and b phases at TE. Thus, for the copper–silver system, the
eutectic reaction, Equation, may be written as follows:
L(71.9 wt% Ag) m cooling heating a(8.0 wt% Ag) + b(91.2 wt% Ag)
Often, the horizontal solidus line at TE is called the eutectic isotherm.
The eutectic reaction, upon cooling, is similar to solidification for pure
components in that the reaction proceeds to completion at a constant
temperature, or isothermally, at TE. However, the solid product of
eutectic solidification is always two solid phases, whereas for a pure
component only a single phase forms. Because of this eutectic reaction,
phase diagrams similar to that in Figure 1 are termed eutectic phase
diagrams; components exhibiting this behavior make up a eutectic
system.
b. What can we benefit from them?

5. 1.Know the phases
2.Status of phases
3.Percentage of each phase
c. What do they show the relationship between?
" temperature and the compositions and quantities of phases at
equilibrium"
d. Are the binary equilibrium the only type ; There is another
phase
ONE-COMPONENT (OR UNARY) PHASE DIAGRAMS :
Much of the information about the control of the phase structure of a
particular system is conveniently and concisely displayed in what is
called a phase diagram, also often termed an equilibrium diagram.
Three externally controllable parameters that affect phase structure—
temperature, pressure, and composition—and phase diagrams are
constructed when various combinations of these parameters are plotted
against one another. Perhaps the simplest and easiest type of phase
diagram to understand is that for a one-component system, in which
composition is held constant (i.e., the phase diagram is for a pure
substance); this means that pressure and temperature are the variables.
This one-component phase diagram (or unary phase diagram,
sometimes also called a pressure–temperature [or P–T] diagram) is
represented as a two dimensional plot of

6. 2.1 Pressure–temperature phase
diagram for H2O. Intersection of the dashed
horizontal line at 1 atm pressure with the solid–
liquid phase boundary (point 2) corresponds
to the melting point at this pressure (T = 0C).
Similarly, point 3, the intersection with the
liquid–vapor boundary, represents the boiling
point (T = 100C)
pressure (ordinate, or vertical axis) versus temperature (abscissa, or horizontal
axis). Most often, the pressure axis is scaled logarithmically.
We illustrate this type of phase diagram and demonstrate its interpretation
using as an example the one for H2O, which is shown in Figure 2.1. Regions
for three different phases—solid, liquid, and vapor—are delineated on the plot.
Each of the phases exist under equilibrium conditions over the temperature–
pressure ranges of its corresponding area. The three curves shown on the plot
(labeled aO, bO, and cO) are phase boundaries; at any point on one of these
curves, the two phases on either side of the curve are in equilibrium (or coexist)
with one another. Equilibrium between solid and vapor phases is along curve
aO—likewise for the solid–liquid boundary, curve bO, and the liquid–vapor
boundary, curve cO. Upon crossing a boundary (as temperature and/or pressure
is altered), one phase transforms into another. For example, at 1 atm pressure,
during heating the solid phase transforms to the liquid phase (i.e., melting
occurs) at the point labeled 2 on Figure 2.1 (i.e., the intersection of the dashed
horizontal line with the solid–liquid phase boundary); this point corresponds to
a temperature of 0C. The reverse transformation (liquid-to-solid, or
solidification) takes place at the same point upon cooling. Similarly, at the
intersection of the dashed line with the liquid–vapor phase boundary (point 3 in
Figure 2.1, at 100C) the liquid transforms into the vapor phase (or vaporizes)
upon heating; condensation occurs for cooling. Finally, solid ice sublimes or
vaporizes upon crossing the curve labeled aO. As may also be noted from

7. Figure 2.1, all three of the phase boundary curves intersect at a common point,
which is labeled O (for this H2O system, at a temperature of 273.16 K and a
pressure of 6.04 * 10-3 atm). This means that at this point only, all of the solid,
liquid, and vapor phases are simultaneously in equilibrium with one another.
Appropriately, this, and any other point on a P–T phase diagram where three
phases are in equilibrium, is called a triple point; sometimes it is also termed
an invariant point inasmuch as its position is distinct, or fixed by definite
values of pressure and temperature. Any deviation from this point by a change
of temperature and/or pressure will cause at least one of the phases to
disappear. Pressure–temperature phase diagrams for a number of substances
have been determined experimentally, which also have solid-, liquid-, and
vapor-phase regions. In those instances when multiple solid phases
(i.e., allotropes, Section 3.6) exist, there appears a region on the diagram for
each solid phase and also other triple points.
5. Discussions and Calculations:
a. What is a phase diagram (thermal equilibrium diagram)
Binary phase diagrams are maps that represent the relationships
between temperature and the compositions and quantities of phases at
equilibrium, which influence the microstructure of an alloy. Many
microstructures develop from phase transformations, the changes that
occur when the temperature is altered (typically upon cooling). This may
involve the transition from one phase to another or the appearance or
disappearance of a phase. Binary phase diagrams are helpful in
predicting phase transformations and the resulting microstructures,
which may have equilibrium or nonequilibrium character.

8. The graph shows the following: To the right, element B is 100% (thus
the ratio of element A is equal to 0%); the left axis is 100% (A and B). The
figure shows that the pure element B melts at a high temperature at L +
B; pure element A has another high melting point at L + A. If we start
with element B and add 10%, for example, from element A (B becomes
90% in the mixture), the melting point of the mixture is reduced
according to the upper line L + B. (Top line L + B is the boundary
between liquid (top) and steel (bottom)). If we increase the proportion
of A in the mixture to 20% A to 80% B, we find that the melting point is
reduced according to the upper line L + B, and we still change the ratio
of the materials until the mixture reaches the lowest temperature fused,
which is point L, It is not necessarily the 50% A and 50% B of the mixture.
The L-shaped point is usually shifted to the right or left according to the
properties of the mixture.
Similarly, if we start from the far left where element A is pure. We do
not mix it with element B in different proportions, we find that its
melting point goes down to point L.
At the point of the yotiki, the mixture is called the base mix or the base
structure, which is characterized by having the lowest melting point
compared to the other proportions of the mixture. This temperature is
called the base point.
The base mixture (or the utechic mixture) has a special crystalline
structure called the superlattice, in which atoms are arranged not only at
the near level but also at the distant level in matter (ie, hundreds or

9. thousands of atoms). The whole mix then melts at the base point, and
the crystalline system of the atoms flows at the same time and becomes
a liquid mixture (magma). Thus, the intrinsic point is the lowest possible
melting point of a combination of elements, occurring at the yotite mix.
Usually the base system is represented in the phases diagram as shown
in the figure above. The etheric point (the yotik point) is defined as the
point that corresponds to the intrinsic temperature and the intrinsic
mass ratio.
b. What is meant by hypo & Eutectic alloys
Hypoeutectoid Alloys
illustrated in Figure 3.1 for the eutectic system. Consider a composition
C0 to the left of the eutectoid, between 0.022 and 0.76 wt% C; this is
termed a hypoeutectoid (“less than eutectoid”) alloy. Cooling an alloy of
this composition is represented by moving down the vertical line yy in
Figure 10.33.At about 875C, point c, the microstructure will consist
entirely of grains of the phase, as shown schematically in the figure. In
cooling to point d, about 775C, which is within the phase region, both
these phases will coexist as in the schematic microstructure. Most of the
small particles will form along the original grain boundaries. The
compositions of both and phases may be determined using the
appropriate tie line; these compositions correspond, respectively, to about
0.020 and 0.40 wt% C. While cooling an alloy through the phase region,
the composition of the ferrite phase changes with temperature along the –
( ) phase boundary, line MN, becoming slightly richer in carbon. On the
other hand, the change in composition of the austenite is more dramatic,
proceeding along the ( ) – boundary, line MO, as the temperature is
reduced. Cooling from point d to e, just above the eutectoid but still in the
region, will produce an increased fraction of the phase and a
microstructure similar to that also shown: the particles will have grown
larger.At this point, the compositions of the and phases

10. 3.1 Schematic representations of the
microstructures for an iron– carbon alloy of hypo eutectoid composition
C0 (containing less than 0.76 wt% C) as it is cooled from within the
austenite phase region to below the eutectoid temperature
are determined by constructing a tie line at the temperature Te; the
phase will contain 0.022 wt% C, whereas the phase will be of the
eutectoid composition, 0.76 wt% C. As the temperature is lowered just
below the eutectoid, to point f, all of the phase that was present at
temperature Te (and having the eutectoid composition) will transform
into pearlite, according to the reaction in Equation
g10.76 wt% C2 Δ cooling heating a10.022 wt% C2 Fe3C 16.70 wt% C2
. There will be virtually no change in the phase that existed at point e in
crossing the eutectoid temperature—it will normally be present as a

11. continuous matrix phase surrounding the isolated pearlite colonies. The
microstructure at point f will appear as the corresponding schematic
inset of Figure 3.1. Thus the ferrite phase will be present both in the
pearlite and as the phase that formed while cooling through the phase
region. The ferrite that is present in the pearlite is called eutectoid
ferrite, whereas the other, that formed above Te, is termed
proeutectoid (meaning “pre- or before eutectoid”) ferrite, as labeled in
Figure 3.1. Figure 3.2 is a photomicrograph of a 0.38-wt% C steel; large,
white regions correspond to the proeutectoid ferrite. For pearlite, the
spacing between the and Fe3C layers varies from grain to grain; some of
the pearlite appears dark because the many close-spaced layers are
unresolved at the magnification of the photomicrograph. Note that two
microconstituents are present in this micrograph—proeutectoid ferrite
and pearlite which will appear in all hypoeutectoid iron–carbon alloys
that are slowly cooled to a temperature below the eutectoid. We use
the lever rule in conjunction with a tie line that extends from the ( Fe3C)
phase boundary (0.022 wt% C) to the eutectoid composition (0.76 wt%
C) inasmuch as pearlite is the transformation product of austenite
having this composition. For example, let us consider an alloy of
composition C0 in Figure 10.35. The fraction of pearlite, Wp, may be
determined according to

12. 3.2 Photomicrograph of a 0.38-wt% C steel having a microstructure consisting of pearlite and
proeutectoid ferrite. 635. (Photomicrograph courtesy of Republic Steel Corporation.)
c. For the given phase diagram Calculate the following
 Percentage of phrases for 1kg 50% wt Sn & 50% Pb at the
following temperatures
 1.100 C
 2. 200 C
 3.300 ° C
 The percentage of the constituents that make the sentences for
the given above

13. 1.100c
c1 = 50% wt sn
ca = 5% wt sn
cB = 99% wt sn
𝑤 𝑎 =
𝑐 𝐵−𝑐1
𝑐 𝐵−𝑐 𝑎
𝑤 𝑎 =
99−50
99−5
= 52.127%
𝑤 𝐵 =
𝑐1−𝑐 𝑎
𝑐 𝐵−𝑐 𝑎
𝑤 𝐵 =
50−5
99−5
= 47.8723%
𝑐𝛽
𝑐 𝑎 𝑐1

14. 2. 200C
c1 = 50% wt sn
ca = 18% wt sn
cB = 57% wt sn
𝑤 𝑎 =
𝑐 𝐵−𝑐1
𝑐 𝐵−𝑐 𝑎
𝑤 𝑎 =
57−50
57−18
= 17.948%
𝑤 𝐵 =
𝑐1−𝑐 𝑎
𝑐 𝐵−𝑐 𝑎
𝑤 𝐵 =
50−18
57−18
= 82.05128%
cBc1
ca

15. 3. 300C
As may be noted, point C1 lies within the Liquid phase field.
Therefore, only the liquid phase is present
𝐶1