Metals

Generally isotropic, and crystalline. Can be made amorphous by melting and then suddenly cooling a sample. Metals can be categorized into 2 types.

Pure Metals

Inter-molecular bonds: Metallic bonds. Commonly not used in the pure form.

Pure metals might be:

• not strong enough
• too weak to corrosion

Alloys

Which contain more than one metallic element.

Examples:

• Steel $[\ce{Fe}+\ce{C}]$
• Cast Iron $[\ce{Fe}+\ce{C}]$
• Brass $[\ce{Cu}+\ce{Zn}]$
• Bronze $[\ce{Cu}+\ce{Sn}]$
• Gold jewelry $[\ce{Au}+\ce{Cu}]$
• Duralumin $[\ce{Al}+\ce{Cu}]$ - used for aircraft body
• Stainless steel $[\ce{Fe}+\ce{C}+\ce{Cr}+\ce{Ni}]$,
• Cast iron $[\ce{Fe}+\ce{C}]$

Alloys have a parent metal (mostly used metal, percentage-wise) and one or more alloying elements (all elements other than parent metal).

Note

Steel has maximum of $2\%\; \ce{C}$ and it’s ductile (won’t break easily). Cast Iron has $2\%-4\% \ce{C}$ and it’s brittle (will break easily).

Super Alloys

Alloys containing too many alloying elements (maybe even 20).

Properties

• $\ce{Fe}, \ce{Co}, \ce{Ni}$, and their alloys are magnetic
• Good electrical conductivity
• Good thermal conductivity
• High strength
• High stiffness (= high young’s modulus)
• Good ductility