Chapter 11: Applications and Processing of Metal Alloys

Ferrous Alloys

a metal mixture where iron (Fe) is the main component, combined with carbon and other elements like chromium, nickel, manganese, or molybdenum

Cast Irons

a hard, strong, and brittle metal alloy made by melting iron with a high carbon content (typically 2% to 4%) and silicon, then pouring the liquid mixture into a mold to cool and harden.

Gray iron

• graphite flakes

• weak & brittle in tension

• stronger in compression

• excellent vibrational dampening

• wear resistant

Ductile iron

• add Mg and/or Ce

• graphite as nodules not flakes

• matrix often pearlite – stronger

but less ductile

White iron

• < 1 wt% Si

• pearlite + cementite

• very hard and brittle

Malleable iron

• heat treat white iron at 800-900°C

• graphite in rosettes

• reasonably strong and ductile

Compacted graphite iron

• relatively high thermal conductivity

• good resistance to thermal shock

• lower oxidation at elevated

temperatures

What are limitations of Ferrous Alloys?

1) Relatively high densities

2) Relatively low electrical conductivities

3) Generally poor corrosion resistance

What are metal fabrication techniques?

forming, casting, miscellaneous

Hardenability

measure of the ability to form martensite

Why does hardness change with distance?

The cooling rate decreases with distance from quenched end.

Precipitation hardening

hardening, strengthening due to formation of precipitate particles. Al, Mg alloys are precipitation hardenable.