Aluminium Alloys Flashcards
What rank is Aluminium in the most abundant elements in the earths crust?
3rd
What are the three stages of aluminium production?
Bauxite - ore dug out of ground
Aluminium Oxide
Aluminium
What is the Bayer Process?
The refining of Bauxite in to Aluminium Oxide
What is the Hall-Heralt Process?
The refining of Aluminium Oxide into Aluminium
At each stage of aluminium production, roughly what percentage of mass is lost?
50%
Describe the Hall-Heralt Process
- Electrolysis of Alumina in cryolite
- Aluminium taped out of electrolysis tank in molten form
- Aluminium filtered, de-gassed, alloying elements added
- Aluminium is casted via DIRECT CHILL.
What is Direct Chill casting?
DC is a non equilibrum solidification sequence giving rise to a heterogenous material. (Micro segregated gamma phase and a by-product brittle eutectic phase)
Why does DC casted aluminium require homogenisation?
To remove the brittle eutectic phase.
What does microsegregated mean?
The same elements are present but different fractions have different concentrations of alloying elements.
What are the consequences of alloying aluminium?
- Worse corrosion resistance
- Worse deformability
- Worse surface finish
- Worse conductivity
- Worse density (in most cases)
Why do we alloy Aluminium?
For increased strength, UTS!!!!
What strengthening mechanisms can be used on Non Heat Treatable Alloys?
grain refinement
solid solution strengthening
cold working
What strengthening mechanisms can be used on Heat Treatable Alloys?
Homogenisation
Natural Ageing
Artificial Ageing
What are the three main classes of non heat treatable alloys?
1XXX - >99% Al
3XXX - 1% Mn
5XXX - up to 6% Mg
What are the three main classes of heat treatable alloys?
2XXX - Cu and sometimes Mg
6XXX - Mg and Si
7XXX - Zn and Mg
