Metals- Aluminium Alloys

Question 1

Two families of aluminium alloy

Answer 1

Those which derive their strength from heat treatments and those which don’t

Question 2

Where do non-heat treatable alloys derive their strength from?

Answer 2

Refinement of grain size, solid solution strengthening and cold working

Question 3

Where do heat treatable alloys derive their strength from?

Answer 3

Mainly precipitation hardening

Question 4

Alloy additions to aluminium

Answer 4

Zn, Mg, Cu, Mn, Si, Li

Question 5

Alloy series 1-7

Answer 5

1XXX- 99% min Al
2XXX- Cu
3XXX- Mn
4XXX- Si
5XXX- Mg
6XXX- Mg and Si
7XXX- Zn

Question 6

Alloys used for aircraft wingskin, fuselage, window frames, drinks cans

Answer 6

Wingskin- Al-Zn-Mg-Cu
Fuselage- Al-Cu
Window frames- Al-Mg-Si
Drinks cans- Al-Mg or Al-Mn

Question 7

What series are the non-heat treatable alloys?

Answer 7

1, 3 and 5 series

Question 8

3XXX series

Answer 8

About 1wt% Mn which forms dispersoids to refine grain size. 3004 has 1.2% Mn and 1% Mg and is recyclable and used for drinks cans

Question 9

5XXX series

Answer 9

Up to 6 wt% Mg. Advantage is lightweight. Disadvantages are weldability, repairability, yield point phenomena

Question 10

2XXX series

Answer 10

Heat treatable. Used for airframe and skin structure. T4 (damage tolerant) condition for lower wing skin

Question 11

7XXX series

Answer 11

Heat treatable. Used in upper wing structures where there are compressive stresses. Weldable. Highest strength of all Al alloys so used for ballistic armour

Question 12

Conventional uses of 6XXX series

Answer 12

Window frames. Heat treatable.

Question 13

6013

Answer 13

Designed to replace 2XXX in aircraft. Less dense and weldable. Has Mg, Si, Cu. Cu counteracts deleterious natural aging