Design 4.2a

• Extracting metal from ore is complex and energy intensive.


  Metals make up a significant portion of the world's crust. However they are not distributed evenly around the world, nor are they often found in pure deposits. Rather, metals are typically found combined with other elements in localized areas. Rock that contains metals that can be economically extracted is called ore.

  Ore deposits are not evenly distributed around the world - they are often localized in certain areas. Moreover, the ore may be mined from one area, and then transported to another area where the metals are extracted.
• Grain size influences the physical and mechanical properties of metals and alloys


  Metals are crystalline structures made up of grains. The size of the grains has an impact on the physical and mechanical properties of a metal.

  Grain size is influenced by the type of heat treatment a metal receives while it is cooling. Manufacturers will apply certain heat treatment to achieve desirable mechanical properties. Essentially, rapid cooling forms small grains, while slow cooling forms large grains.

  
• Alloying


  Alloys are the mixture of one metal with another metal or non-metal.  This combination creates a material that has unique properties than if the metal was just used alone. 

  In general, alloying increases hardness and strength and reduces malleability and ductility.

  Pure iron, for example, is quite soft. By allowing it with carbon, carbon steel can be produced which has much greater strength, and thus is more useful for construction and engineering applications.

  
• Work hardening


  Work hardening is the process of increasing the hardness of a metal through applying a process when the metal is cold. The most common work hardening method is the application of force to compress the grains through cold rolling. 
• Super Alloys are engineered for performance in extreme contexts

  Metal alloys exhibit high degrees of 

  • mechanical strength
  • resistance to corrosion
  • surface stability

  High resistance to creep and high oxidation

  • Creep is the slow expansion or deformation of a material over time. Creep can be exaggerated by high temperatures and prolonged forces. 
  • Oxidation is the reaction of a metal with oxygen. The most familiar of this type of reaction is rust (oxygen reacting with iron in steel).
  • Metals may corrode in the presence of high temperatures and acids or alkalis.
• Tempering



  It is the application of heat after work hardening. This reduces some of the hardness and stiffness and increase the toughness and ductility of the metal.

  
• Sustainability Considerations - Recovery and disposal of metals and metallic alloys

  Metals and metal alloys are easily recyclable.

  Compared to the extraction of raw materials, recycling metals:

  • uses less energy
  • produces less waste
  • uses materials that have already been extracted (thereby reducing the demand to extract more natural resources)

  Metals can be indefinitely recycled, unlike plastics which can degrade in quality and properties through recycling. 
• Metals and metal alloys can be categorized into two categories, depending on whether or not they contain iron.

  Ferrous alloys contain iron, which also makes them magnetic.

  Non-ferrous alloys do not contain iron.
• Ferrous

  Mild Steel

  • Car body parts 
  • General engineering structures
  • nuts, bolts, nails, screws

  Stainless Steel

  • Cutlery
  • Cooking and cleaning surfaces

  Cast Iron

  • Heavy duty machinery
  • vices and clamps
• Non-Ferrous 


  Aluminum

  • Soft drink cans
  • kitchen foil
  • engine components

  Copper

  • printed circuits

  Silver

  Tin

  • solder
  • tin cans

  Zinc

  • Galvanizing - protective coatings that protect against corrosion
• Alloys


  Brass

  • Castings
  • Marine and plumbing fittings (for its corrosion resistance)

  High Speed Steel (HSS)

  • Used for cutting tools such as drills and saw blades.