Aluminium Alloys – OverviewNaveed Akhtar

Contents

1. Introduction

2. Chemistry

3. Classification

4. Applications

5. Manufacturing

6. Heat treatment

7. Common Defects

8. Conclusions

2

Introduction Abundance

Oxygen

Aluminum Oxide / Bauxite

Silicon

Iron

All Others

3

Introduction Advantages

• High strength to weight ratio

• High electrical and thermal conductivity

• High reflectivity and resistance to

corrosion

• Non-toxic (ideal for packaging and cooking

material)

• Ductility-easy to cold work and fabricate

4

History Aluminum Production

• The first commercial batch of Aluminum

was produced in 1888

• Production Capabilities Lower the Price

– Between 1888 and 1893 Aluminum dropped

from $4.86/lb to $.78/lb

5

• Early uses for Aluminum

– Cooking utensils

– Electrical wire and cable

– Foil

– Auto bodies

– Engine parts used by the Wright Brothers’

History Use

6

Chemistry Alloying Elements

Ti, B, Zr, Cr, Ni, Bi, Pb

Cu, Mn, Mg, Si, Zn, Fe

Principal

Alloying

Elements

Additional

Alloying

Elements

7

Role of Alloying Elements

Al

Cu

1. Increases strength and hardness2. If >12% makes the alloy brittle

3. Hot cracking tendency

4. Decreases corrosion resistance

8

Role of Alloying Elements

Al

Mn

1. Increases yield and tensile strength

2. Improves ductility

3. Good resistance to corrosion

4. Decrease resistivity

9

Role of Alloying Elements

Al

Si

1. Increases tensile strength and hardness uptil 13% wt.

2. Decrease the hot cracking

3. Good resistance to corrosion

10

Role of Alloying Elements

Al

Mg

1. Increases strength and hardness

2. Good resistance to corrosion

3. Increase weldability and machinability

11

Role of Alloying Elements

Al

Zn

1. Gives heat treatable alloys when combined with Mg

2. Increase strength and hardness

3. Increased toughness but susceptible to stress corrosion cracking

12

Classification Alloy Designation System

Al

13

Applications 1XXX

14

Applications 2XXX

15

Applications 3XXX

16

Applications 4XXX

17

Applications 5XXX

18

Applications 6XXX

19

Applications 7XXX

20

Production Wrought Al Alloys

21

Extrusion Process

22

Heat Treatment Al Alloys

Annealing Treatment

Solution heat treatment

Precipitation (Hardening) treatment

23

Before Solution Heat Treatment After Solution Heat Treatment

Heat Treatment

24

Heat Treatment

Al-Cu phase diagram showing three steps in precipitation hardening 25

Common Defects

Defect

Casting Defects

Extrusion Defects

Forging Defects

Heat Treatment

Defects

26

Casting Defects

Cracks Porosity

Inclusions Segregation

27

Cracks Types

Radial Loop TransverseCentric

28

Cracks 7075

29

Cracks 2024

30

Inclusions Optical Images

31

Inclusions SEM Images

32

Inclusions SEM Analysis

33

Inclusions Fracture surface

34

Inclusions Fracture surface

35

Extrusion Defects

Extrusion tears/ cracks

Scratches

Fish scalingUn-even wall thickness

Layer Formation

Coarse grain ring

36

Drawing Defects

Scratch Bumped ring

Un-uniformity of wall thickness

Crack

Wrinkle End break

37

Cracks in Extrusion Unetched form

38

Cracks in Extrusion T6 etched form

39

Heat treatment Defects

Unqualified mechanical properties

Over firing

Coarse grain Quenching cracks

40

Grain Coarsening

41

Control of Grain Coarsening

42

43