IT 111 Industrial Metals

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IT 111 Industrial Metals

• Light Metals

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Light Metals

• That group of metallic elements with atomic
  number less than 23
• Beryllium, Magnesium, Aluminum, Titanium,
  Calcium, Potassium, Sodium, Lithium
• (Bold are the only ones used as structural
  metals)

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Aluminum

• Very light in weight
• About 1/3 the weight of steel
• Tensile strength about 13,000 psi
• Steel is about 60,000 psi
• Cold working Aluminum approximately doubles its
  strength
• Can alloy to get as high as 100,000 psi
• Generally, Aluminum loses significant strength
  above 500 deg F
• Melting Point approx 1220 deg F

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Advantages of Aluminum

• High strength to weight ratio
• Good formability
• Inherent anti-corrosion mechanism
• Oxide is a hard coating (crust which seals the
  oxygen from the core
• Excellent electrical conductivity
• Non-sparking and non-magnetic and non-toxic
• Hundreds of alloys having wide range of
  characteristics

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Production of Aluminum

• Most abundant metal (8 of clay) in the earths
  crust but it is always in combination with other
  things
• Bauxite is the most common form of ore which is
  hydrated aluminum oxides (Al2O3 and H2O)
• Bayer process is used to produce alumina from the
  bauxite
• Alumina is then reduced in an electrolytic process

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Alumina Reduction (See Figure)

• Alumina is dissolved in cryolite (sodium alumina
  fluoride)
• Mixture is electrolyzed in an electrolytic cell
• Uses carbon electrodes
• High temperature process greater than 3720 deg
  F
• Molten Aluminum forms and settles to the bottom
  where it is collected
• Cast in ingots

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Wrought Aluminum (sheet, plate, extrusion, rod,
wire)

• Hot rolled after removing surface
• Four digit number
• 1xxx 99 pure aluminum
• 2xxx Copper alloy
• 3xxx Manganese
• 4xxx Silicon
• 5xxx Magnesium
• 6xxx Magnesium and Silicon
• 7xxx - Zinc

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Typical Wrought Alloys

• See Table

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Aluminum Cast Alloys

• Alloys have been developed for good casting
  qualities
• Fluidity of feed, strength, ductility, corrosion
  resistance
• Die Casting compatible Injection Casting
• Numbering system XXX.X
• 1xx.x 99 pure
• 2- Copper, 4- Silicon, 5- Magnesium, 6- Zinc

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Aluminum Cast Alloys

• See Table

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Latest and Greatest

• Metal Matrix Composites (MMC)
• Aluminum reinforced with fibers, whiskers,
  particulates, wires
• Aerospace applications (space shuttle, aluminum
  diesel engine pistons)
• Superplastic forming of aluminum sheets
• Like vacuum forming plastic sheets

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Beryllium

• Very rare metal
• Ore is Bertrandite (of which only 5 is Be)
• BeO is an emerald???
• Very light in weight
• About 2/3 of Aluminum
• Extremely high strength to weight ratio
• Tensile approximately 115,000 psi
• About 5 times high strength steel
• Transparent to X-rays
• Low impact strength
• Very expensive

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Beryllium

• Problems
• Corrodes rapidly in tap or sea water
• Brittle
• Poor ductility
• Airborne particles are very hazardous to lungs
• Occasionally used in aerospace

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Magnesium

• Lightest structural material 2/3 of Al
• Obtained mostly from sea water
• Attributes
• Good fatigue resistance
• Resistant to dents
• Can absorb energy elastically
• Moderate strength but high strength to weight
  ratio
• Weldable

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Magnesium

• Deficiencies
• More expensive than aluminum
• Sensitive to stress concentrations
• Low corrosion resistance
• Molten state burns in air
• Machined chips can become ignited
• Applications
• Aerospace
• Transportation (gearboxes, Mag wheels)

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Magnesium

• See Table

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Titanium

• Similar weight to Aluminum
• Attributes
• Greater strength 85,000 psi
• Superior corrosion resistance
• Non-magnetic
• Weldable
• Blue sparks when machined
• Deficiencies
• Metal galls when drilling and tapping
• More expensive than aluminum (5 vs 1 per pound)

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Titanium

• Applications
• Aerospace
• Orthopedic Implants

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Titanium

• See Table

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Comparison Table
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Comparison by size and weight

• Sorted by dia (small to large)
• Titanium
• Steel
• Beryllium
• Magnesium - Wrought
• Magnesium - Cast
• Aluminum - Cast
• Aluminum - Wrought

• Sorted by weight (small to large)
• Beryllium
• Titanium
• Magnesium - Wrought
• Magnesium - Cast
• Steel
• Aluminum - Cast
• Aluminum - Wrought