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Aluminium Flashcards

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1
Q

What is T3?

A

Solution treated, cold worked and naturally aged to a substantially
stable condition. Allows for cold working to increase strength and also for
cold work involved in flattening or straightening.

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2
Q

What is T4?

A

Solution treated and naturally aged to a substantially stable condition.

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3
Q

What is T6?

A

Solution treated and artificially aged.

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4
Q

What is T7?

A

Solution treated and overaged to lower than peak strength in order to
improve another property e.g. stress corrosion cracking resistance.

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5
Q

What is T73?

A

Solution treated and overaged by a two stage ageing treatment to lower than
peak strength in order to improve SCC resistance.

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6
Q

what is TXX6?

A

(e.g. T736) Indicates the 1st step in a two stage ageing process is the T6
treatment.

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7
Q

What is Tx51?

A

(e.g. T351 & T851) applies to products which receive no further straightening
after stretching, e.g. plate.

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8
Q

What is TX52?

A

(e.g. T7352 & T73652) applies to products that are stress relieved by
compressing after solution treatment (strain typically 1-5%).

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9
Q

What is T8?

A

Solution treated, cold worked and artificially aged beyond peak strength.

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10
Q

What are the properties of aluminium?

A

Low Density
Highly resistant to most forms of corrosion
superb conductor of electricity
Non-Magnetic and noncombustible
non toxic and impervious
strong
ductile

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11
Q

how abundant is aluminium?

A

3rd in the crust

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12
Q

Applications of aluminium?

A

construction
packaging
transport
electrical
other

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13
Q

how is aluminium extracted?

A

Aluminium is extracted from bauxite, a mixed oxide ore
containing about 50% hydrated alumina

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14
Q

What is Bayer Process?

A

It is separated from the other oxides by dissolution and reprecipitation by reaction with sodium hydroxide

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15
Q

What is Hall-Haroult process?

A

It is then dissolved in a molten salt mixture of cryolite (Na3AlF6
)
and electrolytically reduced to molten aluminium

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16
Q

how much power is consumed per tonne of aluminium
produced?

A

14,000 kWh/tonne

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17
Q

Describe the Hall-Heroult Process

A

Graphite anodes
molten Al2O3 and Na3AIF6
Graphite lines tank (cathode)
Al collects molten on the bottom

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18
Q

What kind of process is Hall- Heroult?

A

Continuous
Bath running all the time

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19
Q

What Direct Chill (DC) casting?

A

Semi continous
Liquid metal into water cooled metal mold
Hydraulic ram withdraws aluminium at a draw rate
produces billet

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20
Q

Why do we get eutectic forming in aluminium non-equilibrium?

A

Segregation of 2 different phase elements
Reduces melting temp

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21
Q

How is eutectic removed?

A

Homogenisation
After solidification the alloy is heated to a temp below eutectic temo and held for a long time ( up to 24hrs)

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22
Q

What are the main alloying elements of 1xxx

A

99% min Al

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23
Q

What are the main alloying elements of 2xxx

A

Copper

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24
Q

What are the main alloying elements of 3xxx

A

Manganese

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25
What are the main alloying elements of 4xxx
Silicon
26
What are the main alloying elements of 5xxx
Magnesium
27
What are the main alloying elements of 6xxx
Magnesium and silicon
28
What are the main alloying elements of 7xxx
Zinc
29
What are the main alloying elements of 8xxx
other
30
What do F, O, H and T mean?
F - As fabricated O - annealed wrought H - Cold worked T - Heat Treated
31
What alloys are work hardenable
1xxx 3xxx 5xxx
32
what are some typical applications of 1xxx
foil Architectural Decorations Power transmission
33
What are typical applications of 3xxx
Drinks cans
34
strength of 3xxx, annealed vs cold worked
Annealed - 40 MPa Cold worked - 185MPA
35
how is 3xxx hardened?
SS hardening from Mn Dispersion strengthening via MnAl6 particles
36
what are the advantages of 5xxx aluminium?
Much more recyclable than 3xxx lower densitty does not rust high strength formable bright surface finish
37
What is the strenght of 5xxx annealed vs cold worked?
Annealed - 40-160MPa Cold worked - 300 MPa
38
What are the disadvantages of 5xxx Aluminium
weldability Repairability yield point phenomena
39
what is the main strengthening mechanism of 5xxx aluminium
solid solution strengthening by mg dissolved in Al matrix
40
Why does the strength increase with with SS strengthening in 5xxx aluminium?
Mg has effect on lattice strain
41
What is homogenisation?
After solidification the alloy is heated to a temp below the eutectic temp and held for a very long time ( can be 24 hours) to remove the eutectic and to homogenise the solute content.
42
What does aging temperature determine?
Determines rate of nucleation and growth of precipitates
43
What happens to 1xxx when RX
drop in strength but increase in ductility
44
What effect does ageing time have?
Determines the size of precipitates
45
what are the effects of increases aging temperature?
Decreases undercooling - less driving force for nucleation get fewer nuclei Increases diffusion of solute - precipitates grow faster
46
What are the 3 stages of ageing?
Nucleation Growth Coarsening
47
What does a under aged distribution of precipitates look like?
Large number of very small underdeveloped precipitates
48
What does a peak aged distributions of precipitates look like?
Optimum size and distribution of precipitates
49
What does overaged look like?
A few large precipitates spaced far apart
50
Which alloys are Heat treatable?
2xxx 6xxx 7xxx 8xxx
51
what are the applications of 2xxx aluminium?
Airframe and skin structure T4 (damage tolerant) condition for lower wing Heavy engineering
52
What is the order of strength of 2xxx, 6xxx, 7xxx? lowest to highest
6xxx -> 2xxx -> 7xxx
53
What are some disadvantages of 2xxx
SCC and corrosion resistance are poor
54
How are the highest strengths of 2xxx achieved?
Cold working between quenching and artificial ageing
55
what is the θ Phase for 2xxx?
High Cu:Mg ratio. Excess Cu Al2Cu
56
What is S phase for 2xxx?
Low Cu:Mg Ratio Al2CuMg
57
What are the applications of 6xxx
Structural and architectural applications Door frames 75% of industrial extrusions
58
What are some advantages of 6xxx
Easily extruded at high speeds good anodisable surface finish Good corrosion resistance and weldability
59
6xxx disadvantages
Not as strong as 7xxx Not as thermally stable as 2xxx
60
What can you add to 6xxx to increase strength
Cu
61
What can you add to 6xxx to restore corrosion resistance?
Cr
62
What is the precipitation sequence of 6xxx
SSSS → rod GP zones → β’ needles → equilibrium Mg2Si plates
63
What is the precipitation sequence of 2xxx
SSSS → lath GP zones → S’ laths → S laths.
64
What are the dilute and concentrate makeups of 6xxx additions?
1. Mg + Si < 1 wt. % (Dilute) 2. Mg + Si > 1 wt. % ( concentrate)
65
What are properties of dilute 6xxx?
Age well at RT (natural ageing) -> metastable GP zone GP zones act as nucleation sites during artificial ageing (T6) Homogeneous distribution of Mg2Si precipitates
66
What are the properties of Concentrate 6xxx
Higher strenghs Age well at RT (Natural ageing) -> metastable GP zone T6 reduces strength GP zones redissolve on heating- decrease in nucleation sites for Mg2Si precipitates Need to age immediately after Quench
67
What is the effect of adding silicon to 6xxx ?
AlFeSi phase is detrimentral to billet properties in unspheroidised form β Homogenisation must change this phase to alpha phase extrudability is linked to Si makeup
68
what is the effect of adding magnesium to 6xxx
negligable effect on SolidSolutionHardening in excess it casues dramatic decrease in extrudibility changes tear initiation mechanism decreases ductility and toughness Better corrosion resistance
69
what is the effect of Mg2Si on 6xxx
The principle strengthening phase Equilibrium ratio of Mg:Si is 1.73:1 Improves tensile properties Decrease in extrudability because of cracking Reduces required storage time between storing and artificial ageing due to growth of fine precipitates after ageing Precipitates must be fine and uniformely dispersed
70
What is the effect of adding iron to 6xxx
Can reduce strength can refine Mg2Si precipitates reduction in corrosion resistance increase in toughness grain boundary pinning effect small amounts of Fe means normal grain growth and recrystalisation
71
What are the effects of adding copper to 6xxx
unclear either no effect or reduction in the corrosion resistance increases strength by refining Mg2Si precipitates a small amount of SSH No effect on toughness Improves alloy brightness after bright dripping and anodising
72
What is the effect of adding manganese and chromium to 6xxx
present as impurities or deliberate Increase toughness by fomring incoherent stable dispersoids during homogenisation increase quench sensitivity by providing sites for Mg2Si nucleation Mn preferred as less harmful to finish and extrusion speed
73
What is the effect of adding V to 6xxx?
Increase strength Increase toughness refining grain size during casting
74
What is the effect of adding Pb and B to 6xxx?
Improve machinability
75
What is the effec of adding Zn to 6xxx
Provide solid solution strengthening
76
What is the effect of adding Ti and B to 6xxx
Increase solidifcation rate Influence final grain size
77
What are the applications of 7xxx?
Upper wing structures (compressive stresses) Bridges Tanks Rockets

AerospaceMetals (3 decks)

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