Materials (Weeks 1-6)

Ionic Bonding:

Electrostatic Force (Transferring Electrons)

Covalent Bonding

Sharing Electrons

Metallic Bonding

Packed in lattice Structure (Free electrons)

Elastic Modulus

• Material's stiffness or resistance to elastic (non-permanent) deformation

• The steeper the line, the lower the Elastic modulus

• The slope of the stress/strain curve

Atomic Packing Factor

Volume of atoms in Unit Cell/

Volume of Unit Cell

Theoretical Density

nA/V_cN_a

n for BCC

2

n for FCC

4

n for HCP

6

Bravais Lattice

14 possible geometric arrangements, including BCC, FCC and HCP

FCC Lattice Constant

BCC Lattice Constant

Lattice constant/Lattice parameter (a)

Physical dimension of a unit cell

SEM (Scanning Electron Microscopy)

• Uses focused beam of electrons to produce an image

• 3D image capabilities

• Topography, Morphology and Texture

TEM (Transition Electron Microscopy)

• Beam of electrons through ultra thin sample

• Subcellular, Grain boundaries, material identfication

Edge Dislocation

Extra Half Plane

Screw Dislocation

Spiral Planar ramp resulting from shear deformation

Interstitial diffusion

small atoms, migrate through the spaces (interstitial sites) between larger host atoms in a crystal lattice. the most efficent

Vacancy diffusion

when atoms, of similar size to the host lattice, exchange positions with neighboring vacancies (empty lattice sites), requiring the vacancy to move through the crystal

Stress-Strain curve

Load Displacement Curve

Tensile and compressive Stress

=Force/Area Before Loading

Tensile Strain

Change in length/New length

Sheer stress

Sheer force/Original Area

Compressive strain

Same as tensile but with negative delta

Lateral Strain

Change in length/original width

Possions Ration (v)

Lateral strain/Londituninal strain

Stress Strain Plot

Tensile Strength (TS)

Max point on the stress strain curve

Yield Strength

Stress at which noticeable deformation occurs

• 0.2 offset from x intercept

• Highest pressure at end of elastic modulus

Ductility (EL)

Largest strain before failure

True stress and strain

Always greater than engineering stress

Stress vs Strain

Stress is the internal forces at play, where as strain measured the deformation of the material

Number of Vacanies

Fraction of vacancies x Number of Sites

Number of Sites

Density/Atomic weight x Avodgrados number

Fraction of Vacancies

exp(-Activation Energy/Boltzmans constant x temperature)