Aluminium and its alloys

Question 1

aluminium is extracted from

Answer 1

bauxite ore

Question 2

method of decomposing aluminium oxide

Answer 2

electrolysis

Question 3

Properties of aluminium

Answer 3

excellent resistance to corrosion
high thermal & electrical conductivity
high malleability (compressible)
non-magnetic
soft and ductile

Question 4

methods to improve aluminium low strength

Answer 4

cold working
alloying
alloying followed by heat treatment

Question 5

Uses of aluminium

Answer 5

frying pans, kettles
drink cans, food packaging foils
telescopes

Question 6

how can wrought materials be shaped

Answer 6

forging

rolling

Question 7

properties of wrought materials

Answer 7

ductile and malleable

Question 8

how can cast materials be shaped

Answer 8

sand casting

pressure die-casting

Question 9

properties of cast materials

Answer 9

good fluidity
low shrinkage
short freezing range

Question 10

aluminium alloy number system and meaning of each digit

Answer 10

first digit: major alloying element

last 2 digits: identify the aluminium alloy or aluminium purity

Question 11

effects of cold working on wrought alloys (not heat treatable)

Answer 11

the higher the cold working %, the higher the strength, but lower ductility

Question 12

Elements added to aluminium alloys

Answer 12

copper, magnesium, silicon

Question 13

Duralumin applications

Answer 13

aircraft bodywork

Question 14

How does copper affect aluminium alloy properties and how to prevent it

Answer 14

copper reduces corrosion resistance

improve corrosion resistance by cladding a thin layer of high purity Al (Alclad)

Question 15

Solution treatment temperature for aluminium alloys to reach pure alpha-Al

Answer 15

550 degree C

Question 16

Steps for heat treating of aluminium alloys for 4% copper

Answer 16

1) Coarse precipitates in alpha-Al heated slowly to 550 degree C
2) Quenched in water or oil to form supersaturated solid solution that is ductile
3) Precipitation hardening at 165 degree C for 10 hours (artificial ageing) to obtain extremely fine precipitates in alpha-Al

Question 17

best time to work on aluminium alloys

Answer 17

after solution treatment but before precipitation hardening