Materials ch4

Forging

the manual reshaping of a metal by
hammering or pressing.

Rolling

the thinning of a metal sheet by compressing it
between two rollers

Extrusion

is the pushing of a metal through a die that results in the metal obtaining the shape of the hole

Drawing

the metal is pulled through the die from below rather than being pushed from above

Cold working

is the deformation of a material above its yield strength that results in significant plastic
deformation such that the yield stress increases to the applied stress. Strengthens the material and reduces ductility

Annealing

Reverses the mechanical properties and
microstructure of the metal during cold working can by slowly reducing temperature

3 stages of annealing

• Recovery – large deformed grains form subgrains that result in a reduction of the residual stresses

• Recrystallization – Small grains nucleate at subgrain boundaries, resulting in a reduction in the number of dislocations and a softening that results in the return of the original mechanical properties

• Grain Growth – Small grains grow and consume
  neighboring grains

Hot working

is the deformation above the metal above the recrystallization temperature and it results in a very different microstructure. No strengthening occurs and material remains ductile.

Eutectic point

The point on the eutectic isotherm where the a + b solid solution melts directly to liquid is called the eutectic point

Solvus lines

lines that separate pure phase solids
from mixed phase solids

Eutectoid

invariant points at which one solid
phase is in equilibrium with two different solid
phases

Peretectics

are invariant points in which a solid and
liquid phase are in equilibrium with a different solid phase

Solidus line

Line on a phase diagram below which only solids exist at equilibrium

Liquidus line

Line on a phase diagram above which only liquid exists at equilibrium.

Cementite

A hard, brittle phase of iron carbide (Fe3C) that precipitates out of the steel past the solubility limit for carbon.

Pearlite

Mixture of cementite (Fe3C) and alpha-ferrite named for its resemblance to mother-of-pearl

Austenite

Phase present in steel in which the iron is present in an FCC lattice with higher carbon solubility.

Bainite

Produced by cooling rapidly to between 550°C to 250°C and allowed to remain at that
temperature.

Martensite

Nonequilibrium product of steel formed by the diffusionless transformation of austenite

Spheroidite

Spheroidite is produced by heating bainite or pearlite to just below the eutectoid temperature for 18 to 24 hours

hypereutectoid steel

Steel with carbon percentages above 0.76wt%

hypoeutectoid steel

Steel with carbon percentages below 0.76wt%

Stainless steel

Steel with at least 12% chromium