Solids
The interior angles of the polygons
meeting at a vertex of a polyhedron
add to less than 360 degrees.
1
Platonic Solids
3 triangles at a vertex
Octahedron
4 triangles at a vertex
Icosahedron
5 triangles at a vertex
Cube
3 squares at a vertex
Dodeca
Phase Transformations
Kinetics of Phase Transformation
Avrami Equation
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Rate of a transformation is taken as the reciprocal of
time
required for the transformation to proceed halfway to completion
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Metastable vs Equilibrium State
Stable
Un
Failure of Metals
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Ductile
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Moderately ductile
Brittle
Stages in
Initial necking
small cavity formation
Cup and
Cone fracture
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Crack propagation
fracture
Final shear
coalescence of cavi
to form crack
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Spherical Dimples
Di
Imperfections in solids
1
Why are imperfections important?
Crystal
Structure
+
Bonding
+
Imperfections
Examples:
Secondary processing of metals
Doping in Si
Formation of alloy
Propertie
s
Outline
o Point Defects
o Linear Defects
o Interfacial Defects
o Bu
Fundamentals of
structure of crystalline
solids
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Crystallography
Crystallography is the experimental science of the
arrangement of atoms in solids.
2
Solids
The interior angles of the polygons
meeting at a vertex of a polyhedron
add to less than 360 degr
Diffusion
1
Diffusion is material transport by atomic motion.
It can take place between S-S, S-L, S-G.
Conditions for an atom to diffuse
othere must be an empty adjacent site
othe atom must have sufficient energy to break bonds with its neighbour
atoms an