---
title : "Engineering Physical Metallurgy"
tags : "SEM3, MME"
---

What is MME?
Mining – Metallurgy – Mechanical
669/662

MML 203
- To identify the material from their structures
- To understand the science behind solidification mechanism
- Phase Transformation during heat treatments and alloy systems

# Solidification

## Allotropy
- When the element is existing in a different crystal structure in a given state.

## Comparison of states

- Density - we can comment on the state
- Latent Heat

Solid :arrow_right: Liquid :arrow_right: Gas

$\text{Latent Heat of Fusion } = \frac{1}{40} \text{ Latent Heat of vapour}$

Change in Densities
$\quad \rho_S - \rho_L = 3-4 \%$
$\quad \rho_L - \rho_G = 20 \%$

Position of Liquid is closer to solid than gas

### Entropy
- Entropy is randomness, Randomness is the freedom given to a system to do whatever it wants

#### Cooling Curve of Aluminium



## Free energy
- Energy absorbed and given out

Free atoms :arrow_right: Free Energy :arrow_right: Structure

$\Delta G = \Delta F_V + \Delta F_S + \Delta F_E$

$\Delta G \,\; \text{ - Total Free Energy} \\ \Delta F_V \text{ - Volume Free Energy} \\ \Delta F_S \text{ - Surface Free Energy} \\ \Delta F_E \text{ - Elastic Strain Energy}$

Spherical Shape requires the least amount of energy

$\Delta F_V = (\frac 43 \pi r^3) \delta F_V$

$\Delta F_S = 4\pi r^2 \delta F_S$

$\Delta F_E = 0$

## Nucleation

Nucleation refers to the formation of the first nanocrystallites from molten material

An embryo is a tiny particle of solid that forms from the liquid as atoms cluster together

Critical Radius of Nucleation

$r^* = \frac{2\delta F_S}{\delta F_V}$

- When $r < r^*$
- Embryos are formed
- They are unstable and redissolve back into liquid

- When $r > r^*$
- Embryo will be stable
- Solidification takes place


Critical Free Energy of Radiation

$\Delta F_T^* = \Delta F_V + \Delta F_S + \Delta F_E \\ \qquad = \displaystyle \frac43\pi(r^*)^3\;\delta F_V + 4 \pi(r^*)^2\;\delta F_S + 0 \\ \qquad = \displaystyle\frac{16\pi}{3} \frac{\delta F_S^3}{\delta F_V^2}$

### Homogeneous Nucleation

- Probability of generating nuclei is same throughout
- Temperature of the system is more or less uniform throughout
- It the process of Nucleation where is the rate is constant through out

Undercooling - Reduction below the freezing point

$\Delta T = 0.2 T_m$

$\delta F_V = \displaystyle\frac{\Delta H_f\cdot\Delta T}{\Delta T_m}$

- $R^*$ is larger
- Nucleation and growth process goes together and it is a slow process, hence generate coarser gain structure
- Energy required is more and it is difficult to achieve

#### Effect of Contact Angle

Smaller $\theta$ -> More wettability

### Heterogeneous Nucleation

- The probability of generating nuclei is different
- Temp is different at every location - temp gradient - center to surface
- Undercooling required is 0.02T~m~ that is reasonable small
- $R^*$ is smaller
- Nucleation and growth process will follow each other - fast process - generate finer grain structure
- Nucleation cantake place on impurity atoms
- Energy required is less and it it easy to achieve
:::info
Fine
- More strength
- More hardness
:::

#### Types of Heterogeneous Nucleation
- Surface/Interface Nucleation - Ti, B, Al, Zr
- Innoculation/Nucleating agent
- Addition of Nucleating agent
- Nucleating agent should be
- Powder form/small size,
- stable at solidifcation point
- Must have similar lattice dimension
- By Cavitation

### Cavitation

- Faster Solidfication for harder material
- Vibrating a liquid
- The amplitude of the vibration generates a cavity in the liquid - tiny lifespan
- The collapse of the cavity causes a pressure change which in turn decreases the temperature of the liquid

### Overall Transformation Rate


Number of Nuclei generated at any temperature = $N_T$

$\quad N_T = N_0 \text{ exp} (\frac {-\Delta F_C}{KT})$

$\Delta F_C$ - minimum amount of energy to generate nucleus
K - constant
T - Temperature

### Types of Solidification

1. Planar Growth
- Fast Rate, less time
- Faster heat extraction
- Well-inoculated liquid (Liquid containing nucleating agent) cools under equilibrium conditions
- No need for undercooling since heterogeneous nucleation can occur
- The temperature of solidification front is greater than the freezing temperature
2. Columnar Growth
3. Dendritic Growth
- Slow rate, more time
- Branches

#### Chovorinov's Rule

Time required for solidification - t~s~

$\quad t_s = \displaystyle K\left(\frac VA\right)^n$

t~s~ - Time required for a simple casting to solidify completely
V - Volume of the casting
A - Surface area of the casting in contact with the mold - Surface from which heat can be transfered
n - Constant, usually 2
B - Mold constant

Thickness d of the solidified skin grows -

$d = k_{\text{solidification}}\sqrt t-c_1$

t - time after pouring
k~solidification~ - constant for a given casting material and mold
c_1 - pouring temperature

Solidification time affects the size of the dendrites - measured in Secondary Dendrite Arm Spacing (SDAS)

SDAS = kt~s~^m^

m and k - constants that depend on the compostion of the metal

#### Dendritic Solidification in Pure Metal


- Not well-inoculated - Undercooling necessary
- As nucleation begins latent heat of fusion is released which causes the temperature of the liquid to increase - Recalescence
- Thermal arrest - produced because the evolution of the latent heat of fusion balances the heat being lost because of cooling
- Heat extraction - creates hot zone
- In dendritic Heat flow direction and dendritic growth direction are at an angle of 180^o^
- Dendritic fraction solidified $f = \frac {c \Delta T}{\Delta H_f}$

#### Dendritic Solidification in Alloy system

- Binary Sytem - 2 components
- Ternary System - 3 Components

---
t = 5s
Fine Grain equviaxed grains - Produced by fast heat extraction

t = 15s
Chill zone causes formation of columnar zone
Elongated Structure Grain
Reigon at center - liquid

t = 25s
Liquid -> Columnar Zone -> Chill Zone
Slow Heat Transfer


Shrinkage Pipe - Volume Contraction

### Solidification Defects

- Inclusions
- Shrinkage
- Gas Porosity
- Segregation

#### Shrinkage

- T~p~ - Temperature Poured - $700^\circ C$
- T~m~ - Melting Point - $660 ^ \circ C$
- Dendritic Shrinkage - Dendrites block channels of the liquid metals

#### Gas Porosity

- Gases dissolve in liquid metal to a larger extent
- T~p~ -> T~m~ -> RT
- Gasses are released in form of bubbles
- Sievert's Law - %Gas = $k \sqrt{P_\text{Gas}}$
- Degasifier - Si /Al - Reduce gas - Killed Steel and Rimmed Steel
- Deoxidizer - FeMn, FeSim CaSi - O~2~ as slag - FeO SiO~2~
- Controlling the Partial Pressure can control the Gas Porosity

#### Segregation

- Pig Iron
- Variation in the composition - deviation from standard distrubution of elements
- Pure Metal Solidifies First and then the impurities are thrown at the center to solidify last
- Interdendritic Segregation - Coring
- Segregation can be minimised by Homogenization - Prolonged heating to high temp - to ensure uniform spread of elements

#### Inclusion

Furnace(refractory) - Molten Metal - Crucible or laddle (ceramic) - mold cavity - solidified structure

Particles enter the liquid metal become integral part of the solidified structure

Types
- Exogeneous - Outside Particles
- Indigenous - Generated in system - chemical reaction, slag

# Crystallography

+ Bond parameters
- Bond Length
- Bond Angle
- Bond Enthalpy
- Bond Polarity
- Bond Order

- How do atoms assemble into solid structures?
- Density depends on Structure
- When do material properties vary with the sample orientation?

### Classification of materials based on the type of atomic order

A. Monoatomic
B. Amorphous
C. Liquid Crystals
D. Crystalline Materials

## Crystal Structure

Atomic Structure - Number of protons and neutrons in the nucleus of an atom, as well as the number and probability distribution of electrons
Crystal Structure - Arrangement of atoms in the crystalline solid material

We need a way to specify crystallographic direction and planes

### Lattice

A lattice is an infinite array of points in space, each having identical surroundings to the others.

Their Lengths are called lattice constants, or lattice parameters

### Unit Cell

The smallest group of atoms which can generate the entire crystal by translation

The length of each unit cell axis is called a lattice parameter

C - Cubic
T - Tetragonal
O - Orthohombic
M - Monoclinic
H - Hexagonal
R - Rhombohedral
T - Triclinic


Energy and Packing
- Non Dense, Random packing - Longer bond length
- Dense, Regular packing 0 shorter bond length

Dense - structures tend to have lower energy

### Metallic Crystals

- Densely packed
- Only one element is present - same atomic radii
- Metallic bonding is non directional
- Simple crystal structures

#### Simple Cubic Structure (SC)

Example - Polonium
Rare - poor packing

- Coordination Number = 6
- Atomic Packing Factor (APF) = 0.52
- $R = 0.5a$

#### Body Centered Cubic Structure (BCC)

Close Packed directions are cube diagonals

- Coordination Number = 8
- APF = 0.68
- $\sqrt 3a = 4R$

#### Face Centered Cubic Structure (FCC)

Close packed directions are face diagonals

- Coordination Number = 12
- APF = 0.74
- $4R = \sqrt 2a$
- ABC Stacking

#### Hexagonal Close-Packed Structure

- Coordinate number = 12
- APF = 0.74
- AB Stacking

#### Close Packed Structure

- Closed packed stacking in HCP takes place along the c direction - the (0001) plane
- Closed plane stacking is along (111) plane in FCC


### Theoretical Density

$\qquad \rho = \frac {nA}{V_c N_A}$
n - atoms/unit cell
A - Atomic weight(g/mol)
V~c~ - Volume/Unit Cell (cm^3^/unit cell)
N~A~ - Avogadro's Number (6.023 x 10^23^ atoms/mol)

### Polymorphism and Allotropy

Allotropy - Existence of element in a different structure in the same state

## Crystal Imperfections

- These imperfection influences mechanical properties
- Melting Point is not affect by crystal imperfection

Crystal Imperfections are the defects in the regular geometrical arrangement of the atoms in a Crystalline solid

- Perfect Crystal is an idealization
- Defects - cause - crystal deformations, rapid cooling from high temp or high energy radiation striking the solid

Imperfection Classification

- Point defects
- Vacancy atoms
- Self-Interstitial atoms
- Impurities - Substitutional and Interstitial atoms
- Line defects
- Discloctions
- Volume/Surface defects
- Grain Boundaries
- Stacking Faults
- Twin Boundary

### Point Defects

Vacancies - Vacant atomic sites in a structure

Self-Interstitials - "extra" atoms positioned between atomic sites

Substitutional impurity - impurity atom in lattice
Interstitial impurity - impurity atom not in regular lattice site

Defects
1. Vacancies
- A timplest point defect in a crstal
- Refers to missing atoms or vacant atomic site
- Arises wither from imperfect packing during original crystallisation or from thermal vibrations at high temperatures
2. Frenkel Defect
- It is formed by a cation leaving its normal position and movin into an interstial site
3. Schottky Defect
- It is formed by removing one cation and one anion from the interior of the cystal and then placing them both at an external surface
4. Compositon Defects
- These arise from impurity atoms during crystallisation
- Substitutional or Interstitial
5. Electronic Defects
- These are the errors in charge distribution in solids
- These are primarily necessary in electrical conductivity and related phenomenon
- Prominent example is pn junction and transistor junction

### Solid Solutions

Substitutional - atoms of the parent metal are replaced or substituted by atoms of the alloying metal

Intersitial - The atoms of the parent or solvent metal are bigger than the atoms of the alloying or solute metal - smaller atoms fit into interstices i.e. spaces between the larger atoms

## Line Defects

Deformation of deuctile materials occure when a line defect (dislocation) moves (slip) through the material

Dislocations
- Are line defects
- Slip between crystal planes
- Produce permanent (plastic)

1-D defets around which some of the atoms are misaligned

These are responsible for the useful property of ductility in metals, ceramics and crystalline polymers

Types
- Edge Dislocation
- Screw Dislocation

### Edge Dislocation

Edge dislocation centers around the edge dislocation line that is defined along the end of the extra half-plane of atoms

- Distortion - to the lattice decreases with distance away from dislocation line
- Burgers - vector b - defines the magnitude and direction of the deformation
- Edge dislocation b and dislocation line are perpendicular

#### Motion of Edge Dislocation

Dislocation motion requires the successive bumping (slip) of a half plane of atoms

- Bonds across the slipping planes are broken and remade in succession
- Plastic permanent deformation of most crystalline - dislocation
- Dislocations introduced - solidification, plastic deformation, and rapid cooling (thermal stresses)
- To deform plastically means to slide atomic plane past each other
- Caterpillar type movement


Burgers Vector
- The magnitude and direction - lattice distortion associated with a dislocation
- If Burger Vector and the oreintation of the dislocation line are known, then the disclotion is completely described
- This vector indicates how much and at what direction the lattic above the slip plane appears to have been shifted with respect to the lattice below the plane
- Burger vector - perpendicular to dislocation line in Edge Dislocation and parallel in Screw Dislocation

### Screw Dislocation

- Screw dislocation is ramped step in crystal planes
- Burger vector which defines the direction of the atoms displacement for a screw dislocation is parallel to the line of dislocation

### Slip

Crystallographic Requirements
- Burger vector for unit dislocations must joint crystallographically equivalent positions in the lattice
- The motion of the dislocation must transport atoms from one equilibrium position to another

Most favorable Burgers vector is the shortest vector that connect equivalent lattic positions

### Planar defects

- Two dimensional defects
- Arise from a change in the stacking of atomic planes on or across a boundary

#### External surface Imperfections

- Imperfections represented by a boundary
- The external surface of a material is an imperfection itself because the bonds do not extend beyond it since surface atoms are not entirely surrounded by other atoms on other side - they posses higher energy

#### Internal Surface Imperfections

These are manifested by such defects as grain boundaries, Tilt boundaries, twin boundaries, stacking faults

# Phase Diagrams

When we combine two elements - what equilibrium state do we get?

- Composition
- Temperature

How many phases to we get?
How much of each phase do we get?

Components of a system - Independent chemical species which comprise the system

## Phase

Physically distinct chemically homogenous and mechanically separable region of a system (e.g gas, crystal, amorphous)

- Gaseous state always a single phase
- mixed at atomic or molecular level
- Liquid State
- Solution in a single phase (NaCl in H~2~O)
- Liquid mixture consistes of two or more phases
- Solids
- In general due to several compositions and crystals structure many phases are possible
- For the same composition different crystal structures represent different phases
- For the same crystal strucure different compositon represent different phases

Phase Transformation - the change of one phase into another

Grain - The single crystalline part of polycrystalline metal separated by similar entities by a grain boundary

Microstructure - Structures requiring magnificaitons in the region of 10 to 1000 times

### The Gibb's Phase Rule

For a system in equilibrium

F = C - P + 2

F - Degree of Freedom
C - Number of Components
P - Number of Phases

Modified Gibbs Phase Rule
- When Pressure is constant - Metallurgical system

F = C - P + 1

:::info
F - Degree of Freedom
C + 1/2 - What we can control + (P&T / T)
P - What System controls
:::

C = 2 - Binary
C = 3 - Ternary

### Equilibrium Phase Diagram

- Dipicts the existence of different phase of a system unfer equilibrium
- Solubility limit curves - Equilibrium or constutional diagram

## Possibilities of Alloy Formation


| Nature | Liquid State | Solid State |
| -------- | -------- | -------- |
| Completely Miscible | Yes | Miscible(B),<br> Partially Miscible(C\),<br> Immiscible(D) |
| Completely Immiscible | No | No Immisicible (A) |




Liquidus - Boundary between L+S and Liquid state

Solidus - Boundary between L+S and Solid State

Constitutional Supercooling - Change in composition with change in Temperature

## Tie Line and Lever Rule


$\text{Fraction of One Phase} = \frac {\text {Length of the Tie Line from the overwall compostion to the opther phase Boundary}}{\text{Total Length of the Line}}$


1. Wherever two phases are in equilibrium (1083 < T < 1453)

## Hume Rothery Rule

In order for an alloy system to have unlimited solid solubility, certain conditions must be satisfied -

- Size Factor
- The radius of solute and solvent atom should be within limit of ±15% - To minimize the lattice strain
- Crystal Structure Factor
- It is always desirable to have same crystal structure of both the components, to get continous solid solubility
- Relative Valency Factor
- If the materials are of same valency, it is always better
- The metal if higher valency will dissolve to a larger extent in metal of lower valency than the extent to which latter dissolves in former
- Electrochemical Factor
- The two metals must be as close as possible in EMF series to get solution

Exceptions
- Cu-Ag
- Size factor Borderline
- All factors are favourable
- Produces terminal solid solution with 8% Ag and 8.8% Cu
- Cu-Zn
- Cu-Mg
- Mg-Pb

## Hagg's Law/ISS Formation

Interstitial Solid Solution Formation

In order to get ISS the radius ratio should be greater than 41%

### Size Factor Compound

- When there is appreciable difference in atomic diameters

Indicates
- High Melting Points
- Hard/Brittle
- Conductors

$\text{Ratio} = \displaystyle \frac{r_{\text{interstitial}}}{r_{\text{solvent}}}$

$0.41 < \text{Ratio} \leq 0.59$ - Interstitial Compounds are formed

Borides/Nitrides/Carbides of transitional elements occurs over a small range of composition

Mostly formula is M~2~X or MX

TiC, ZrN, Cr~2~N, V~2~C, VN, WC

$\text{Ratio}\geq 0.59$ - Distortion in the parent lattice is too large - results in complexe structures

### Electron Compounds

- Formation of intermediate phase with specific e/a ratio
- Westgen and Hume Rothery Compound
- Size Ratio - 1.4 to 1.5
- Bonding is like metallic solid solution - Secondary solid solutions
- Brittle when complex otherwise ductile
- Conductive

| e/a | Phase observed | Structure | Examples |
| -------- | -------- | -------- | -- |
| 3/2 | ß | BCC, HCP | ß-Brass, Cu~3~Al, Ag~2~Al(HCP) |
| 27/13 | Γ | Complex Cubic | Γ-Brass, Cu~5~Zn~8~ |
| 7/4 | ε | HCP | CuZn~3~, Cu~3~Sn, Cu~3~Si |

To find e/a ratio, assumed valency of metals are

1 - Cu, Ag, Au
2 - Mg, Zn, Cd, Be
3 - Al
4 - Sn, Si, Ge
5 - Sb
0 - Transtition Metals (Fe, Ni, Co, Pt, Mo)

Mg~2~Sn - 8/3 (2.66)
Mg~2~Pb - 4/1 (4)
NiAl - 5/2 (2.5)

### Electrochemical Compounds

- Follow Valency Law
- Bonded by Ionic Homopolar covalent
- Range of Solid Solubility is restricted
- Hard Brittle Semi-conductor
- Atomic Size difference is above solid solubility limit
- Constant Melting Point
- Crystal structure corresponds to definite chemical formula of compound like NaCl, CaF2

Homo ZnS - ZnTe, AlSb
Ionic NaCl - MgSe, BaTe

Ionic CaF~2~ - Mg~2~Sn, Mg~2~Pb

### Lave's Phases

- Hard
- Stable at high temp
- Phases will have compostions according to AB~2~ formula
- Apparent metallic bonding
- When difference between atomic radii of two elements is about 20-30%

Reason for formation - Diff in AtRadii about 22.5% - Compounds get packed in a crystal dtrucure whose coordination number is more than 12

## Invarient Reactions

F = 0

Liquid state (-tic) - Eutectic, Peritectic, Monotectic

Solid State (-toid) - Eutectoid, Peritectoid


### Eutectic reaction

$L \rightarrow \alpha + \beta$

Eutectic - Easy melting - The alloy of eutectic composition freezes at a lower temperature than the melting points of the constituent components

Eutectic microstructkure

All the alloys before the Eutectic reaction are thr hypo eutectic allow

Phase before Eutectic reaction - pro-eutectic phase

All the alloys after the Eutectic reaction are the hyper eutectic

Eutectic will always precipitate

Alternate Lamilar structure

#### Isomorphous System

Same Structure - Continous solid solubility type equilibrium diagram


### Free Energy - Composition Diagram


At T1 - Liquid is stable because its free energy is less that Solid

At T2 - Melting Point

### Cooling Curves

Bumps on T vs time curves are transformation changes

### Eutectic Diagram

Melting point difference is small
Complete Solid Immiscibility
Temp ofWute


## Eutectoid Reaction

Hyper Eutectoid -

## Fe-C Equilibrium Diagram

Steel and Cast Iron

3 Interstitial solid solutions
- α-Ferrite
- Austenite
- δ-Ferrite


Iron Carbon alloy - up to 2% Carbon is Steel beyond it Cast Iron

1495°C - Peritectic REaction

1130°C - Eutectic Reaction - Ledeburite

723°C - Eutectoid Reaction

A~0~ - Curie Temp of Cementite
A~1~ - 723°C - Allotropic Transformation
A~2~ - 768°C - Curie Temp
A~3~ - 723-710°C - Eutectoid Transformation - allotropic transformation
A~4~ - 1495°C
Acm

### Allotropic Forms of Iron

- α-Fe
- BCC
- RT to 910°C
- 32% voids
- Diameter of space available - 0.36Å
- $\gamma$-Fe
- FCC
- 910-1400°C
- 26% voids
- Diameter of space available - 0.52Å
- δ-Fe
- BCC

### Fe-C

Steel/Cast Iron
- Interstitial solid solution
- α-Ferrite
- Austenite
- δ-Ferrite
- Intermetallic compound

#### Peritectic Reaction (1495°C)

δ-Ferrite (Solid Solution, 0.1%C) + Liquid Iron(0.5%C) ⇌
Austenite(0.15%C)

Maximum Solubility of Austenite is 2% at 1130°C

Eutectic Reaction (1130°C)

Liquid Iron(4.35%C) Asutenite(2.0%C) + Cementite(6.67%C

Ledeburite

Cementite
- Metastable phase - Hardest Phase
- Dissociates Fe~3~C 3Fe+C
- Slow Cooling
- Presence of Silicon
- High Temp
- Radius Ratio 0.63
- Complex Structure

730 - 723 - 710

Sample preparation

Rough Polishing - Emery Paper
Cloth Polishing - Velvet cloth
Etching - 2% NITAL (2% HNO~3~ in Ethyl Alcohol)

Differential Reflection

Shadowing Effect of Pearlite


## Classification of Steel

### Based on % carbon

Extra low C steel (0 - 0.008/0.1)
Low C steel (0.1-0.2)
High C steel (0.5-0.8)
Extra high C steel (>0.8%C)

### Based on content/Additions

- Mild Steel
- 0.2/0.3%C
- 0.5/%Si
- 0.8/0.9%Mn
- 0.005%S and P

- Low alloy steel (<2% addition)
- Hadfield Mn Steel

### Based on phases in steel

Ferritic steel
Austenitic steel
Ferrito-peralitic steel
Martensitic steel
Pearlitic Steel

### Indian Nomenclature

Martensite

- Large amount of C in compressed in the BCC structure

BCT - c/a > 1

## Cast Iron

More than 2% C

Casted Component - Brittle material - cannot be machined

Casting - Heat till Liquid - fill it in cavity and generate required shape

Graphite - Free form of Carbon
Flakes
Rossettes
Nodules

Fe~3~C - unstable
- High Si(>1.5%) - Get independent graphite
- High Temperature (>1000°C)
- Cooling Rate - Slow cooling will convert into graphite

Fe~3~C -> 3Fe + C

### White Cast Iron

Combined form of Carbon - Cementite and Pearlite
Brittle
White cluster of crack

### Grey Cast Iron

Free form of carbon colour of the fracture surface is Grey
Produces lines on paper

Advantage of Graphite -
- Damping out vibrations
- Vibrations are transfered to the metallic matrix

Strength of GCI

- Type of Matrix
- Ferrite - Soft - 125-50 VPN
- Freeite Pearlite - Medium
- Peralite - Hard - 250-280 VPN
- %C and %Si
- As per Mauver's Diagram
- Rate of Cooling
- From 723°C
- Slow - F GCI
- Medium - F+P GCI
- Fast - P GCI
- Size of graphite flakes
- ASTM - 8 Sizes of grains
- 1 - >4 inches
- 8 - <1/16 inches
- 1 - Weak
- 8 - Strong
- Distrinbution of graphite flakes
- ASTM - 5 distribution - A, B, C, D, E
- Type B - Rosette
- Type A - Uniform Distribution
- Type C - Random Orientation and Random sizes
- Type E - Interdendritic segregation
- Type D -
- Additions in CGI
- CaSi, FeSi, Ca, Zr, Al - Nucleating materials - Fine powder and uniform distribution
- Reactions to graphitization

Ferritic 25kg/^2^
Pearlitic 35kg/mm^2^

Meehanite
- Innoculation technique
- Fine size
- Faster Solidification
- 50kg/mm^2^

Iron-Silicon Alloy

# Microstructure

1) Identify the microstructure from its alloying elements
2) Observe and analyse the microstructure of carbon steel and cast iron
3) Learn the effect of carbon weight percent on the microstructure of steel and cast iron

0.1% Carbon Steel

α - Ferrite and Pearlite

WCI -

Modification

Converting Coarser eutectic to finer eutectic

Conversion of hyper into hypo structure

Shifting of eutectic composition and eutectic temperature

Precipitation Hardening alloy

Artificial

Aluminium Alloy - 2014, 2017, 2024

2017 - Natural heating alloy - Duralumin