Aluminium

Question 1

Why use aluminium?

Answer 1

has a low density (1/3 weight of steel)
highly resistant to most forms of corrosion - Protective coating Al oxide barrier to air, temperature, moisture and
chemical attack.
* Superb conductor of electricity replaced Cu in many situations where weight
is also a consideration.
* Non-magnetic and non-combustible, advanced industries such as electronics
or in off-shore structures.
* Non-toxic and impervious – food packaging
IT has a very high abundance - but this can be problematic as it is hard to extract as it is contained in things like clay hence why iron tends to get extracted more

Question 2

How can aluminium alloys be split up and organised?

Answer 2

they are split into the thousand groups:
1XXX Aluminium of ~99% minimum purity - used in packaging/ quite soft
2XXX Aluminium-copper alloys
3XXX Aluminium-manganese alloys
4XXX Aluminium-silicon alloys
5XXX Aluminium-magnesium alloys
6XXX Aluminium-magnesium-silicon alloys
7XXX Aluminium-zinc-magnesium alloys
8XXX + 9XXX Miscellaneous alloys

Question 3

How does aluminium get split into 2 groups?

Answer 3

work hardening alloys and heat treatable alloys

Question 4

what are work hardening alloys?

Answer 4

Hardened by deformation i.e. an increase in dislocation density
Designated
F = As fabricated
H = Strain hardened
O = Annealed state
& dislocations

Question 5

What are heat treatable alloys?

Answer 5

Properties controlled by heat treatment through the dissolution and controlled precipitation of second phase particles (solution treatment and aging)
Designated T (with a number to indicate the treatment)

Question 6

How can the precipitation of the metal be controlled?

Answer 6

at 2.5% all of the copper will be dissolved and it is 100% alpha when its been heated
This can then be quenched in water to create a solid supersaturated solution and the copper wont have time to precipitate out. This structure is not at equilibrium but is at room temperature however if it is left here we will then see precipitation form on the boundaries.
With strength/hardness against time precipitation clusters initially form and then grow (with increasing hardness/strength) however when the material starts to over age the hardness/strength decreases. These can be artificially aged by holding them at specific temperatures for set time.

Question 7

What are the heat treatment of alloys and designations

Answer 7

F - Fabricated
O - Annealed wrought products
only
H - Cold Worked
1. Cold worked only —- 2. ¼ Hard
2. Cold worked and partially annealed —-4. ½ Hard OR
6. ¾ Hard
3. Cold worked and stabilised —- 8. Hard OR 9. Extra Hard
T - Heat treated (stable)
1.Partial solution plus natural aged
2. Annealed cast products
3. Solution heat treated plus cold work
4. Solution heat treated plus natural ageing
5. Artificially aged only
6. Solution heat treated plus artificial ageing
7. Solution heat treated plus stabilising
8. Solution heat treated plus cold work plus
artificial ageing
9. Solution heat treated plus artificial aging plus
cold work