4.2a - Metals and Metallic Alloys

Extracting Metal from Ore

Extraction takes place locally with added value often occurring in another country. Example: Australia mines iron ore which is shipped to China and Japan for steel production.

Grain Size (Metals)

Metals are crystalline structures with grain size affecting properties like strength and toughness.

Grain Size - Heat Treatment

Reheating and cooling metals modifies grain size: slow cooling forms larger grains

Grain Size - Properties

Grain size affects tensile strength (coarse = stronger)

Alloying

Alloys are mixtures containing at least one metal

Examples of Alloys

Bronze (Cu + Sn) and Carbon Steels (Fe + C).

Work Hardening

Toughening metal through plastic deformation

Tempering

A heat treatment process increasing toughness and ductility while decreasing hardness and brittleness.

Superalloys

Alloys with excellent strength

Creep

Permanent deformation of metal due to long-term exposure to stress below its yield strength

Oxidation Resistance

The ability of a material to resist oxygen attacks

Recovery and Disposal of Metals

Metals and alloys are widely recyclable

Ferrous Alloys

Contain iron and are magnetic. Examples: Mild steel

Non-Ferrous Alloys

Contain no iron and are not magnetic. Examples: Aluminum

Mild Steel

Ferrous alloy with 0.1-0.3% carbon and 99.7-99.9% iron

Pro: Low carbon steel that is ductile, malleable, and easily welded, making it suitable for a variety of structural applications.

Con: Prone to corrosion and rusting without proper treatment.

Stainless Steel

Iron

Pro: an alloy of iron, chromium, and nickel that is resistant to corrosion and staining.

Con: It's generally less ductile than other steel alloys and can be more expensive to produce.

Cast Iron

2-6% carbon and 94-98% iron

Pro: It is known for its excellent castability, wear resistance, and machinability, making it ideal for various applications such as engine blocks and machinery components.

Con: It is brittle and can fracture under impact or stress, limiting its use in structural applications.

Aluminum

Lightweight non-ferrous alloy

Pro: high strength-to-weight ratio, durability and doesn’t rust

Con: has lower corrosion resistance compared to some metals like stainless steel.

Copper

Conducts heat and electricity

Pro: very malleable and ductile, used in wiring and plumbing.

Con: prone to corrosion and tarnishing.

Brass

Copper and zinc alloy

Pro: known for its yellow color and corrosion resistance. It is commonly used in musical instruments, plumbing, and decorative items.

Con: can be susceptible to dezincification and has lower strength compared to some other metals.

Silver

Natural or alloyed with copper (sterling silver)

Pro: a precious metal known for its conductivity and luster, commonly used in jewelry, electronics, and silverware.

Con: may tarnish over time, requiring maintenance.

Lead

Heavy

Pro: metal known for its high density and malleability, often used in batteries

Con: toxic properties and environmental hazards, particularly when ingested or inhaled.