The document provides information on solidification processes and binary alloy systems. It discusses: 1) The three main steps in the solidification process: formation of stable nuclei, growth of nuclei into crystals, and formation of a grain structure. 2) The different types of solid solutions including substitutional and interstitial solid solutions. Substitutional solutions involve solute atoms replacing solvent atoms, while interstitial solutions involve solute atoms filling spaces between solvent atoms. 3) Phase diagrams and how they represent the relationship between temperature, composition, and phases in equilibrium for a binary alloy system. Key points include liquidus lines, triple points, and using phase diagrams to interpret cooling curves. 4) An

1. CHAPTER 1
Part 2
MATERIAL STRUCTURE
AND
BINARY ALLOY SYSTEM

2. Metal and Alloy Solidification
• is a phase transformation from liquid to solid to have the
desired shape ( semi-finished or finished products)
• Processes involving solidification : welding, soldering, casting
and glass forming
• 3 steps in solidification process:
 Formation of stable nuclei in the melt
 Growth of nuclei into crystals
 Formation of a grain structure.

3. Solidification of Metals
a. Formation of stable nuclei (nucleation)
b. Nucleation growth into crystal
c. Formation of grain structure
a b c

4. Stages of Grain Growth
• Crystal nuclei commence to form around microscopic impurities.
This is called nucleation.
• Dendrites begin to form crystal nuclei. These dendrites will have
primary and secondary arms.
• Dendrites continue to grow, forming tertiary arms, which meet
and join.
• Dendrites thicken up and fill in. When arms of one dendrite touch
those of adjacent dendrites, growth ceases and grain boundaries
are established.
• When metal is completely solid, little evidence of dendrite growth
remains and only the grain boundaries are visible.

5.  Formed as a result of adding of impurity atoms to a metal.
 is an alloy in which one element is dissolved in another to form a single-
phase structure without changing the crystal structure and no new
structures are formed.
SOLUTE and SOLVENT
 2 types of solid solutions :-
 Substitutional Solid Solution
 Interstitial Solid Solution
Solid Solutions
•Dissolved element or solute atoms
•Element or compound present in a
minor concentration
•Can be either metallic or nonmetal
•Base element or host atoms
•Element or compound present in a
greatest amount
•metallic

6. • Solute or impurity atoms replace or substitute the
solvent atoms.
Zinc (solute)
dissolve
Copper (solvent)
Substitutional Solid Solution
Brass
 Zinc is dissolved in Copper to form Brass.

7.  Several features of solute and solvent atoms that
determine the formation of substitutional solid solution.
The atomic radii of the 2 elements must be
similar with the difference in atomic radii less than
±15%.
Their crystal structures for metals of both atoms must
be the same.
Substitutional Solid Solution

8. • Solute or impurity atoms fills the voids or vacant spaces among
the solvent atoms.
dissolve
Iron
(solvent)Carbon (solute)
Interstitial Solid Solution
Steel
 Carbon is dissolved in Iron to form Steel.

9.  Several features of solute and solvent atoms that
determine the formation of Interstitial solid solution.
The solvent atom must have more than one valence.
The atomic radii of the solute atom must be smaller
than the atomic radius for the solvent atom.
Interstitial Solid Solution

10. The Difference Between
METAL and ALLOY
METAL ALLOY
made up of only one element alloy is a mixture of metals, or metal
and non-metal
High ductility Low ductility
Lack of mechanical properties (tensile
strength, yield strength, hardness)
Superior mechanical properties
Lack of strength High strength
Low melting point high melting point
Example:
Copper, Zinc
Example :
Brass , Steel

11. Cooling Curve
And
Phase Diagram

12. Heating and Cooling curve
• Heating curve – graph that shows
phase changes as a substance is
heated
• Cooling Curve – graph that shows phase changes as a
substance is cooled.
** when you go through
a phase change, the
temperature is constant
but you are adding/losing
heat not temperature.
0 t1 t2 t3 t4
0 t1 t2 t3 t4

13. Cooling Curve

14. Cooling Curve

15. Equilibrium Phase Diagram
• Represents the relationship between temperature and
the compositions and the quantities of phases at
equilibrium.
• Temperature and composition are the variable
parameters for binary alloys.
• Pressure is also a parameter that influences
• A binary alloy is one that consists 2 components.

16. Phase Diagram
• Triple Point – point where temperature + pressure conditions allow all
3 states to exists at once.
• Critical Point – T&P above this point do not allow water to exist as
liquid.
For every substance the phase diagram is different.
Water
Melting point = freezing point = 0˚C
Boiling point = condensing pt=100˚C
• Phase Diagram = show at
varying pressure and
temperature what state or
phase the substance is in.

17. Binary Phase diagram

18. Terms In Equilibrium Phase Diagram
• Phase : a homogeneous portion of a system that has uniform physical and
chemical characteristics.
• Equilibrium Phase Diagram: is a convenient and concise way of
representing the most stable relationship between phases. The state of a
system where the phase characteristics remains constant over time periods.
• Compositions : the relative content of a particular element within an alloy,
usually expressed in weight percent or atom percent.
• Liquidus : the line or boundary separating liquid and liquid+solid phase
region on a binary phase diagram.

19. Cooling Curve for Cu-Ni System

20. Phase diagram for
Cu-Ni system

21. • At temperature below about 1080˚C, Cu and Ni are mutually
soluble in each other in the solid state for all composition.
• The Cu-Ni system is termed as isomorphous (solid has the
same structure for all composition) because if this complete
liquid and solid solubility of the two components.
• Liquid L is a homogeneous
liquid solution composed of
both Cu and Ni.
• Solid phase is a substitution
solid solution consisting both
CU and Ni.

22. Point a

23. Point b

24. Point c

25. Point d

26. Point e

27. Point f

28. Find and draw the
IRON-CARBON PHASE DIAGRAM
to discuss with your friends in next class.
** Everyone must have your own
diagram**