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Material Science
Solidification of Metals
19
Engineering
Undergraduate 1
03/09/2011

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Term
Crystalline
Definition
material that has 3 dimensional arrangement to its atoms in the solid state
Term
Amorphous
Definition
material that does not have a 3 dimensional arrangement to its atoms in the solid state
Term
3 common crystal structures of Metals
Definition
1) Face Centered Cubic
2) Body Centered Cubic
3) Hexagonal Close Packed
Term
Face Centered Cubic (FCC)
Definition
tend to be soft and ductile (Al, Pb, Cu)
Term
Body Centered Cubic (BCC)
Definition
tend to be stronger and less ductile (Fe at room temp)
Term
Hexagonal Close Packed (HCP)
Definition
tend to be brittle (Zn, Mg)
Term
Allotropic Phase Transformation
Definition
metals that change crystal structure with temperature
Term
3 Stages of Solidification of Metals
Definition
1) Nucleation
2) Growth
3) Formation of Grain Boundries
Term
Nucleation (stage 1)
Definition
atoms that are close together form a chemical bond
occurs at various locations in the metal
Term
Growth (stage 2)
Definition
additional atoms bond to the nuclei formed in stage 1
growth occurs in 3 dimensions
Term
Formation of Grain Boundaries (stage 3)
Definition
where grains of different orientation meet
Term
Grain
Definition
area within a metal where the atoms have the same orientation
Term
Grain Boundaries
Definition
area where grains of different orientation meet
Term
Small grain size
Definition
stronger and less ductile
Term
Large grain size
Definition
lower strength and higher ductility
Term
Rapid solidification causes...
Slow solidification causes...
Definition
... smaller grain size
... larger grain size
Term
2 common crystal defects
Definition
1) Vacancies
2) Dislocations
Term
Vacancies
Definition
missing atoms at the same locations within a metals crystal structure
these control diffusion
Term
Dislocations
Definition
missing 1/2 planes of atoms in a metals crystal structure
dislocation motion is what allows a metal to Plastically Deform
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