Engineering Materials: Properties, Types, and Classifications

Posted on Aug 10, 2025 in Electromechanical Engineering

Metallic Materials

Characterized by thermal and electrical conductivity, and other key properties.

Iron

  • Properties: Soft, ductile, malleable.
  • Density (PE): 7.86 kg/dm³
  • Melting Point (PF): 1530 °C

Cast Iron

  • Classified by Manufacturing Process:
    • First Fusion
    • Secondary Fusion
    • Malleable (by heat treatment)
    • Hardened (by rapid cooling)
  • Classified by Composition:
    • Gray Cast Iron
    • Nodular Cast Iron (improved toughness and ductility)
    • White Cast Iron
    • Alloy Cast Iron

Steel

  • Classified by Composition:
    • Carbon Steel (only iron and carbon)
    • Special Steel (containing other elements)
    • Ultra-High Strength Steel (special treatment)
    • Stainless Steel
    • Tool Steel

Copper

  • Density (PE): 8.9 kg/dm³
  • Melting Point (PF): 1083 °C
  • Properties: Ductile, malleable, and resistant to liquid corrosion.

Copper Alloys

  • Brasses: Copper and zinc components.
  • Bronze: Copper and tin (variations may include other metals like phosphorus).

Aluminum

  • Density (PE): 2.7 kg/dm³
  • Melting Point (PF): 658 °C
  • Properties: Soft, ductile, conductive, stable in air.

Aluminum Alloys

  • Copper: Increases mechanical strength, decreases corrosion resistance.
  • Zinc: Less resistant to shock.
  • Silicon: Less commonly used.
  • Nickel: Low corrosion resistance.
  • Manganese: Increases corrosion resistance.
  • Titanium: Greater resistance to fatigue.
  • Magnesium: Enhanced corrosion resistance.

Tin

  • Density (PE): 7.3 kg/dm³
  • Melting Point (PF): 232 °C
  • Properties: Flexible and malleable when cold, easily oxidized. Often used for protective coatings on other metals.

Lead

  • Density (PE): 11.34 kg/dm³
  • Melting Point (PF): 327 °C
  • Properties: Flexible, heavy, malleable, with low resistance.

Lead Alloys

  • Solder (tin and lead)
  • Antifriction Metals
  • Printing Metal
  • Hard Lead (for toys)

Zinc

  • Density (PE): 7.5 kg/dm³
  • Melting Point (PF): 419 °C
  • Properties: Malleable, not fragile, with low resistance when cold; acquires resistance when hot.

Titanium

  • Density (PE): 4.5 g/cm³
  • Melting Point (PF): 1660 °C
  • Properties: Lightweight, tough, hard, with excellent corrosion resistance.

Ceramic Materials

General Characteristics: High hardness, high melting points, often brittle, good insulators.

Traditional Ceramics

Typically clay-based materials.

Glass

Characterized by an amorphous structure.

Advanced Ceramics

  • Oxides

    • E.g., Alumina (Al2O3): low corrosion resistance, low conductivity.

  • Carbides

    • High hardness and wear resistance, used in tools.

  • Nitrides

    • Generally fragile.
    • Silicon Nitride: resistance to thermal shock.
    • Boron Nitride: extreme hardness.
    • Titanium Nitride: good wear resistance.

Plastics

Characterized by complex geometries, low density, load-bearing capacity, low conductivity, and corrosion resistance.

Thermoplastics

Can be heated and reshaped multiple times.

  • Acetals

    • Resistant to solvents and wear.

  • ABS

    • Good surface hardness.

  • Fluoropolymers

    • Resistant to high temperatures.

  • Polyamide

    • Wear-resistant.

  • Polycarbonate

    • High toughness.

  • Polyester

    • Wear-resistant.

  • Polyethylene

    • Abrasion-resistant.

  • Polypropylene

    • Abrasion-resistant, good surface hardness.

Thermosets

Cannot be reheated or reshaped after initial curing (tend to crack).

  • Epoxy

    • Resistant to heat and chemical agents.

  • Polyester

    • Used in plastic composites.

Composite Materials

Organic Matrix Composites

  • Polymer Matrix

    • Distributes stress among fibers.

  • Structure Types

    • Laminar
    • Sandwich
    • Honeycomb