Transcript Day20das - Rose

DAY 20: MORE ON METALS
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Titanium
Copper
Magnesium
Zinc
Nickel
Superalloys
Material selection discussion.
TITANIUM
Light metal: 4.5 g/cm3 vs 7.9 g/cm3 for steel.
 Can be very strong: UTS up to 200 ksi.
Competitive with steel at a fraction of the weight,
but you have to pay the price.
 Very corrosion resistant. Forms a tenacious
passive oxide layer on the surface.
 Very reactive at high temperatures. Has to be
produced in special process. Expensive.
 3’ x 2’ x 3/16 in will cost about $1300.
 Titanium Overview (double click to access)
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MORE ON TITANIUM
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Wikipedia says up to 77 tons will be used in each
A-380.
Extremely corrosion resistant.
Now also seeing commodity use. Be
careful, it might be a fake. I.e. golf
clubs!
Komsomolets: Soviet era
attack sub had Titanium
hull.
OR DID IT?
COPPER
Heavier than Fe, about 9.0 gm/cc.
 One of the earliest metals. MP 1100C.
 In unalloyed form, not very strong, but extremely
ductile. Yield: 5 Ksi, UTS: 30.5 Ksi, %EL = 60%.
 Electical conductivity is key to its use in all kinds
of electrical equipment and conductors.
 Copper is also the base metal for two families of
alloys:
1. Brasses (with Zn)
2. Bronzes (with Sn and other metals)
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BRASS
Very attractive metal.
 Excellent corrosion resistance.
 Excellent ductility
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Cartridge brass: 30%Zn
Yield 63 Ksi
UTS 76 Ksi
Ductility %EL = 8%
(After cold working.)
BRONZE
Numerous alloys based on Sn, Ni, Aluminum, etc.
 Tin bronze: UTS is 45 ksi, Yield is 22 ksi, %EL =
25%. (Cast alloy)
 Used for bearings, bushings, fittings and gears.
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MAGNESIUM
Very light metal. Density is about 1.7 gm/cm3.
HCP crystal structure.
 Elastic modulus and strength low.
 Some alloys may be precipitation hardened. Get
up to 50 ksi.
 Ductility somewhat limited. Around 10-15%.
 Clearly this metal has an excellent
strength/weight ratio – used in the aircraft
industry.
 Is also castable. Used as a substitue for plastic in
casings for computers and other such stuff.
 Corrosion resistance ok in normal environments,
but quite poor in challenging environments.
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MAGNESIUM
http://www.store.commoto.com
/images/hypermotardmagnesium-clutc.jpg
http://photography-onthe.net/forum/showthread.php?t=57119 7
http://www.asiagiken.co.jp/english/image/application07.jpg
ZINC
Inexpensive
 Not strong, UTS about 5 Ksi. Not a strength
metal.
 MP about 420 C– Castable YES. Very good for
cheap commodity castings
 Very active metal! Used widely for plating steel.
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ZINC USAGE
http://alloydie.com/images/Zinc3.jpg
www.industrialmetalcasting.com/zinc-casting.html
NICKEL
http://minerals.usgs.gov/minerals/pubs/commodity/nickel/myb1-2006-nicke.pdf
NICKEL
Most of all nickel produced goes into stainless
steel
 80% Ni/20% Cr alloys have been used as heating
elements.
 A major application of electroless nickel today is
in computer hard discs
 Rechargeable batteries can be nickel-cadmium or
nickel metal
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http://www.nickelinstitute.org/index.cfm/ci_id/16/la_id/1.htmhydride
SUPERALLOYS
These alloys are intended to be as strong as
possible at high temperatures.
 The base metal is Fe, Co, or Ni. The latter is
most often used in aircraft engines.
 The most common solutes are Al and Ti. Result
is two main phases: g and g’.Actually, many
different metals are added as solutes to achieve
various strengthening effects.
 It is possible to get a turbine blade which is a
single crystal, later to be strengthened with the
precipitation of the second phase.
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MATERIALS SELECTION
Brief Example
 Each group will try to pick a number of candidate
materials that meet the requirements of each
device.
 Some groups will be selected to make reports.
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