Plastic- Intro and Aluminium Refresh

Question 1

Which Al alloys are used for aircraft wingskin, fuselage, window frames and drinks cans?

Answer 1

Wingskin: Al-Zn-Mg-Cu (7xxx)
Fuselage: Al-Cu (2xxx)
Window frames: Al-Mg-Si (6xxx)
Drinks cans: Al-Mg or Al-Mn (3xxx)

Question 2

What are wrought products?

Answer 2

Ones that have had some work done to them.
Like rolled plate or sheet, extrusions.

Question 3

The heat treatable and non-heat treatable Al alloys

Answer 3

Non-HT: 3, 5, 1xxx
HT: 2, 7, 6xxx

Question 4

Where to find flash cards for info about different alloy classes

Answer 4

MAT333 light alloys flash card decks

Question 5

AA5083 case study

Answer 5

Pages 14 to 20. Don’t know if needed

Question 6

Generic production route of Al alloys

Answer 6

Casting
Pre-working treatments
Hot working
Cold working
Post processing
Finishing

Question 7

When is homogenisation and why is it important?

Answer 7

Is a pre-hot working step. Heat the DC ingots for varying lengths of time (alloy dependent). Reduces micro (and macro) segregation. Poor homogenisation treatments lead to problems during hot working

Question 8

When is solution treatment and why is it important?

Answer 8

Post working treatment for heat treatable alloys. Purpose is to take back into solid solution as much as possible all the alloy additions that contribute to age hardening.

Question 9

Ideal conditions for solution treatment

Answer 9

As near to the solidus temperature as possible for as short a time as possible. Can’t go above or will get some melting

Question 10

Why is control of furnace atmosphere important for solution treatment?

Answer 10

Moisture can lead to injection of H and surface blisters. Fluoride salt in the furnace

Question 11

What happens after solution treatment?

Answer 11

Metal usually quenched and stored at low temperature to reduce natural ageing

Question 12

Problems with quenching

Answer 12

Can lead to residual stresses which can cause distortion or failure. Slower quenching through critical region (400 to 290) leads to reduction in achievable strength after ageing.

Question 13

How to reduce distortions due to quenching

Answer 13

Use controlled cooling, i.e quench into hot or boiling water

Question 14

Final step of processing

Answer 14

Ageing. Artificial, natural, multi step (optimise corrosion resistance)

Question 15

Typical artificial ageing conditions

Answer 15

100-190C for 8-16h

Question 16

Alloy condition letters

Answer 16

F- as fabricated
H- cold worked
O- annealed
T- fully heat treated
W solution heat treated

Question 17

Heat treat designations

Answer 17

See slide 28

Question 18

Which alloy series is used for most extrusions?

Answer 18

6xxx

Question 19

Which 6xxx series alloy was designed to replace 2xxx in aircraft and why?

Answer 19

6013. Less dense and is weldable. Contains some copper to counteract deleterious natural ageing. Used for lower fuselage skin