Metallic Bonding

Interstitial

• Atoms varying in size

• Makes heavier (increase mass)

• Makes stronger

• TOO much = brittle

Substitutional

• Atom replaced by another

• Same energy level atoms

• More malleable

• Doesn’t add much weight

Alloy

homogeneous mixture of mostly metals

Ductility

when solid can be stretched into a wire shape under tension

What holds e- sea together?

Attraction between delocalized electrons and metal cations (electrostatic attraction)

Structure of metals means

strong, hard, high melting point

More e- put into sea =

tougher metal + higher melting point (why transition metals so strong)

Forces in sea

Attraction and repulsion, but keep balance

Unit cells

make up crystal lattice, different depending on packing

Linear defects (dislocations) def

a number of atoms offset from usual place

Types of linear defects

Edge (extra half plane of atoms, moves over when struck until outside lattice), screw (one block atoms shifted wrong, if you follow down, make a screw, shifts down when struck)

Point defects def

effect 1 location in lattice

Types of point defects

Vacancy (atom missing), Interstitial, Substitutional

Dislocation motion

breaking + reforming atomic bonds, irreversible

Many dislocations =

stronger (dislocations get tangled + prevent from moving through lattice)

Dislocations happen easiest

along planes where atoms are closest

Grains def

different lattices colliding, separated by grain boundaries

Grain boundary strengthening

Inoculants (adding impurities at more points), cooling (rapid makes more grains)

Work hardening

plastic deforming (making more dislocations)

Solid solution strengthening

adding alloys (harder for dislocations to happen)

Percipitation hardening

heat to increase 2nd phase particles (increase strength)

Oxidization =

loss of e-

Sublimation

how mirrors made