Day 20: More on Metals 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)

More on Titanium 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: Brasses (with Zn) Bronzes (with Sn and other metals)

Brass Very attractive metal. Excellent corrosion resistance. Excellent ductility 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.

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.

Magnesium http://photography-on-the.net/forum/showthread.php?t=57119 7 http://www.store.commoto.com/images/hypermotard-magnesium-clutc.jpg 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.

Zinc Usage www.industrialmetalcasting.com/zinc-casting.html 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 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.

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.