Transcript Chapter 3 Structure and manufacturing Properties of Metals

Chapter 3
Structure and manufacturing Properties of Metals
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Crystal structure of metals
Role of various imperfections
Importance of grain
Failure and fracture of metals
Ferrous and non-ferrous metals, alloys
Covalent Bond
Some Common Features of Materials with Covalent Bonds:
•Hard
•Good insulators
•Transparent
•Brittle or cleave rather than deform
Metallic bond
Some Common Features of Materials with Metallic Bonds:
•Good electrical and thermal conductors due to their free valence electrons
•Opaque
•Relatively ductile
Ionic Bond
Some Common Features of Materials with Ionic Bonds:
•Hard
•Good insulators
•Transparent
•Brittle or cleave rather than deform
Body-Centered Cubic
(BCC) Structure
Face Centered Cubic
(FCC) Structure
Hexagonal Close Packed
(HPC) Structure
the atoms in rows A and C
are no longer aligned
cubic lattice structures allow slippage to occur more easily than noncubic lattices, so hcp metals are not as ductile as the fcc metals.
Defect
a)
b)
c)
d)
e)
f)
g)
h)
Interstitial impurity atom
Edge dislocation
Self interstitial atom
Vacancy
Precipitate of impurity atoms
Vacancy type dislocation loop
Interstitial type dislocation loop
Substitutional impurity atom
a dislocation is a crystallographic defect,
or irregularity, within a crystal structure
Simple Cubic Lattice showing atomic
planes (marked in red)
Edge dislocation
Burgers vector in black,
dislocation line in blue.
Screw dislocation
Edge Dislocation
Screw Dislocation
Grain
a) Nucleation of crystals
b) crystal growth
c) irregular grains form as crystals grow together
d) grain boundaries as seen in a microscope
Atoms along the boundary
packed less efficiently
more disordered
Grain Boundary
Polycrystalline Deformation
before
after