CHEM111E: Chemistry of Engineering Materials - Metals

Learning Objectives

• Distinguish different types of fuels.
• Calculate the energy derived from fuels.

Content Overview

1. Structure of Metals
2. Properties of Metals
3. Classification of Metals

Introduction

• Metals: Greek "metallon" (mine/quarry).
• 25% of Earth's crust is metal.
• Used in construction, tools, jewelry, etc.
• History: Copper (Bronze Age), Gold, Silver, Iron smelting (~1500 B.C.), Steel (~1200 B.C.).

1. Structure of Metals

• Metals are mostly crystalline solids at room temperature.
• Exception: Cesium, Gallium, Mercury (liquid at room temp).
• Atoms arranged in orderly stacked layers.
• Unit cells: Smallest crystal lattice unit retaining structure.

Common Structures

• Hexagonal Close-Packed (hcp): Atoms at hexagonal prism corners, center of hexagonal faces.
• Face-Centered Cubic (fcc): Atoms at cube corners, centers of cube faces.
• Body-Centered Cubic (bcc): Atoms at cube corners, one at cube center.

2. Properties of Metals

• Metallic Luster: Shiny, lustrous appearance.
• High Thermal/Electrical Conductivity: Electron mobility allows heat/electricity transfer.
• Malleability: Can be hammered into sheets.
• Ductility: Can be stretched into wires.
• Close-packed structures (fcc, hcp) show higher malleability and ductility.

3. Classification of Metals

Ferrous Metals

• Contain Iron (Fe): Magnetic, strong, prone to corrosion.
• Examples:
  • Pig Iron: 92% iron, brittle, used in steel.
  • Cast Iron: Brittle, for pipes/machinery.
  • Wrought Iron: Ductile, corrosion-resistant, used in bolts/nuts.
  • Steel: Iron with carbon/alloy elements (high tensile strength, durable).
    • Carbon Steel: Used for pressure applications.
    • Alloy Steel (e.g., Stainless Steel): Corrosion-resistant, used in utensils/equipment.

Non-Ferrous Metals

• Do Not Contain Iron: Non-magnetic.
• Examples:
  • Aluminum (Al): Light, corrosion-resistant, used in appliances/electronics.
  • Copper (Cu): High conductivity, used in wiring/plumbing.
  • Titanium (Ti): Strong, corrosion-resistant, used in aerospace/biomedical.
  • Zinc (Zn): Corrosion-resistant, used for galvanization.
  • Lead (Pb): Corrosion-resistant, toxic, used in batteries/radiation protection.

Summary

• Structures of Metals: hcp, fcc, bcc.
• Properties of Metals: Luster, conductivity, malleability, ductility.
• Classification of Metals: Ferrous vs. Non-Ferrous.

References

• Askeland, D. et. al. (2010). The Science and Engineering of Materials (6th Ed).
• Mortimer, Charles E. (1975). Chemistry: A Conceptual Approach (3rd ed.).
• Russell, A. M; Lee, K. L. (2005). Structure–Property Relations in Nonferrous Metals.