Arrangement Flashcards
What does increasing the grain sizes do?
Soften the material
What is an amorphous material
Non crystalline material which are disordered
What is a a crystalline material
A material which is ordered and packed into 3D arrays
What is a single crystal
Repeating unit
Rate
Grown by directional solidification
Expensive
Properties vary with different directions/orientation and are said to be anisotropic
Different directions in a crystal have different packing
What is a polycrystalline material
Comprised of many small crystals or grains interlocked
If individual grains have random orientation, the bulk material is isotopic.
Grains can also be textured, increasing directional alignment resulting in anisotropic properties
Simple cubic
APF of 52.4%
1 atom
r=a/2
Po
What is a BCC
APF 68.0%
2 atoms
r = root 3/4 a
Sodium, potassium, iron
What is a FCC
APF = 74%
4 atoms
r = root2/4 a
Nickel, copper, aluminium
HCP
6 atoms
Magnesium, calcium, zinc
Formula for density
nA/VcNa
Where n = unit cell
A= atomic weight
Vc = Volume if unit cell
Na = 6.023 x 10^23
FCC = 2R ROOT 2 BCC = 4R/root 3
What is polymorphism
Where materials can exist in more than one crystal structure
What is allotropy
Where a polycrystalline material is an elemental solid
Ie carbon
What is isotopic
Uniform in all directions
What is anisotropic
Different in different directions
