Manufacturing Technology - Lecture 2: Engineering Materials

Manufacturing Technology - Lecture 2: Engineering Materials

• Material Components of a Car:
  • Ferrous metals make up 65% of a car's materials.
  • Plastics make up 10%.
  • Aluminum makes up 6%.
  • Other materials (textiles, fluids, electrical components, and glass) each represent smaller percentages.

Classification of Engineering Materials

• Materials are categorized into four main groups:
  • Metals
  • Polymers
  • Ceramics
  • Composites

Metals

• Ferrous Metals:

  • Contain iron (Fe).
  • Examples include steels, stainless steels, and cast irons.
  • Wrought iron (pure iron) has a melting temperature of 1539°C.

• Non-Ferrous Metals:

  • Do not contain iron (Fe).
  • Examples include gold, silver, aluminum, copper, and titanium.

• Types of Steel:

  • Plain carbon steel: iron carbon alloy with less than 2% carbon.
  • Alloy steel: some elements are added to improve its properties (e.g., nickel-chromium steel, or stainless steel).
  • Cast iron: iron carbon alloy with more than 2% carbon, and a relatively low melting temperature.

• Aluminum:

  • Melting temperature of 658°C.
  • Good rust resistance.
  • Light in weight.
  • Used in kitchenware and other manufacturing applications.

• Copper:

  • Melting temperature of 1083°C.
  • Used in cables.
  • Copper + Zinc = Brass
  • Copper + Tin = Bronze

Polymers

• Thermoplastics:

  • Can be molded or reshaped above a specific temperature.
  • Return to solid state upon cooling, and can be repeatedly molded.

• Thermosets:

  • Do not become moldable once they cool down.
  • Irreversible cure, often through heat or chemical reaction.

Ceramics

• Compounds of metallic and non-metallic elements.
• Examples include glass, diamond, oxides, nitrides, and carbides.

Composites

• Combinations of two or more chemically distinct materials.
• Their physical properties are superior to their individual components.
• High strength-to-weight ratio.

Crystal Structure of Materials

• Crystalline structure: The arrangement of atoms in a crystal.
• Unit cell: The smallest repeating group of atoms in a crystal structure, showing its characteristics.

Metallic Crystal Structures (Unit Cell)

• Body-Centered Cubic (BCC): Examples include chromium, iron, molybdenum, and tungsten.
• Face-Centered Cubic (FCC): Examples include aluminum, copper, gold, lead, and nickel.
• Hexagonal Closed Pack (HCP): Examples include magnesium, titanium, and zinc.

Material Selection

• Factors affecting material selection:
  • Function of the material
  • Shape of the object
  • Manufacturing processes
• Material Properties: Density, mechanical strength, high temperature stability.
• Relationship between Function, Shape, Process and Material -These factors are interconnected and cannot be separated. Shape, function, and process all impact material selection, and reciprocally, the material selection influences the other factors.