1. Types of phase diagrams

2. •TYPE-1: Two metals are completely soluble in
liquid state and solid states
• Two metals are
completely soluble in the
solid state, the type od
solid phase formed will
be substitution solid
solution.
• The diagram show the
series of cooling curves
for different alloys in a
completely soluble
system. The dotted lines
the form of phase
diagram.
• The diagram plotting
temperature vs.
composition.

3. • The cooling curves pure
metals A and B show only
a horizontal line because
the beginning and end of
solidification take place at
constant temperature.
• These cooling curves
show two changes in
slope.
• The first break is at
temperature T1, which
indicates beginning od
solidification and lower
break at T2 indicates end
of solidification
• The two points TA and
TB represent the
freezing point at two
pure metals

4. • Liquidus line: is upper
line showing the
beginning of
solidification
• Solidus line: is the
lower line showing
the end of
solidification.
• Between the liquidus
and solidus lines
there exists a two
phases region.
• Two phase region
does not give any
information regarding
mixture
• In order to determine
this information, It is
necessary to apply
two rules.

5. • Rule-1: Chemical
composition of phases
• To determine the actual chemical
composition of the phases of an alloy in
equilibrium at any specified temperature in
two phases region, draw horizontal
temperature line called tie line
• Draw the tie line mo to the boundaries of the
field
• Point m the intersection of the tie line with
the solidus line, when dropped to base line,
give the composition od phase that exits
boundry.
• Similarly, point O, when droppedto base line,
will give the composition of the other phase
constituting the mixture, in this liquid solution
of composition.

6. • Rule-2: Relative amount
of each phases
• To determine the relative amounts of the two
phases in equilibrium at specified
temperature in a two phase region
• A vertical line represting the alloy and
horizontal temperature line to the boundaries
of the field.
• The vertical line will divide the horizontal line
into two parts whose length are inversely
proportional to amount of phases present.
This is also known as the lever rule.
• The lever rule may be expressed
mathematically as

7. •TYPE-2: Two metals completely soluble in the liquid
state and completely insoluble in the solid state
• This type of phase diagram is
produce, when the two alloy
components A and B are
completely soluble in the
liquid state but completely
insoluble in solid state.
• The points M and N indicate
the melting points of two pure
metals.
• T1 show the beginning of
solidification and TE end of
solidification.
• MEN is liquidus line and
show beginning of
solidification.
• The point at which the
liquidus lines intersect the
minimum point E, is known
as the eutectic point. TE is
called eutectic temperature.

8. • This phase diagram
consists of four
areas.
• The area above the
liquidus line is a
single-phase
homogenous liquid
solution.
• The remaining three
areas are two phase
areas
• The alloys to left of
the eutectic
composition as
hypoeutectic alloys
and those to right as
hypereutectic alloys.

9. • Alloy 1: is eutectic
composition
• It is cooled from
temperature To it
remains a unifrom
liquid solution intil
the point E, the
eutectic
temperature line is
reached
• The eutectic
reaction may be
written as

10. • The amount of percentage A and L determine by lever
rule

11. •TYPE-3: Two metals completely soluble in liquid
state but only partly soluble in solid state
• This type of phase diagram
show the partial solid
solubility.
• TA and TB indicate the
melting points of two pure
metals.
• TAETB is liquidus line and
TAFEGTB show solidus line
• Above the liquidus line, the
is only single phase liquid
solution.
• The lines FH and GH show
that with the deceasing the
temperature the maximum
amount of solute can be
dissolve deceases.

12. • In alloy 1: liquidus line is
cross T1 it will begin to
solidify by forming crystals
of α solid solution
extremely rich in A.
• The process continuous
with liquid getting richer in
B and gradually moving
down along the liquidus
line.
• The α solid solution also
getting richer in B, moving
down along the solidus
line.
• When the solidus line
crossed at T4 and with
diffusion keeping pace with
crystal growth the entire
solid will be homogenous α
solid solution.

13. • Alloy 2: is the eutectic
composition and
remains liquid until the
eutectic temperature
is reached at point E.
• Since this is also the
solidus line, the liquid
now undergoes the
eutectic reaction, at
constant temperature
• The eutectic reaction
may be written as

14. • The lever rule is a tool used to determine weight percentages of
each phase of equilibrium phase diagram.
• The relative amounts of α and β in the eutectic mixture may be
determined by lever rule

15. Type-4: Congruent melting phase diagram
• When one phase changes into another phase
isothermally (at constt. Temp) without any change
in chemical composition, it is said to be congruent
phase change or congruent phase
transformation.
• All the pure metals solidify congruently.
• Any intermediate phase may be treated as
another component on a phase diagram.
• If the intermediate phase has a narrow range of
composition, it is then represented by a vertical
line on the phase diagram and lebeled with the
chemical formula of

16. the compound.
• If the intermediate phase exists over a long range
of composition, it is recently represented by
Greek letters like alpha.
• In figure 1, an intermediate alloy is shown by a
vertical line. Since it is a compound, it is denoted
by AmBn
• Where m and n are sub-scripts which shows the
number of atoms combined in the compound.
• For example, magnesium and tin form an
intermediate phase which has the chemical
formula Mg2Sn
• In this case, Mg is equal to A, 2 is equal to m, Sn

17. is equal to B and 1 is equal to n.
• It is apparent from the figure 1 that A-B system
can be separated into two parts; one showing all
alloys between A and the compound AmBn and
the other showing all alloys between B and
compound AmBn
• If the compound shows no solubility for either
metal and pure metals shows some solubility for
each other, then phase diagram will be as shown
in figure 2.
• This diagram shows two different eutectic
mixtures. The eutectic reactions’ equations may
be written as follows…

19. Thanks for your
concentration.
Try to do your grip strong
on phase diagrams to be a
great metallurgical engineer…