38 terms

MATSE 259

Exam 1 Vocab
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Yield Strength
Yield strength defined at intersection of .002 offset of stress- strain curve
Tensile Strength
Strength at the maximum of the stress-strain curve
Ductility
Measure of degree of plastic deformation that is sustained at fracture
Resilience
Capacity of a material to asorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered
Toughness
Measure of the ability of a material to absorb energy up to fracture.
Area under the curve up to point of fracture (energy/unit volume)
ductile material
Experiences significant plastic deformation upon fracture
Brittle Material
Experiences very little or no plastic deformation upon fracture
Hardness
Measure of a material's resistance to localized plastic deformation
Unit Cell
Basic structural unit or building block of the crystal structure by
virtue of its geometry and the atom positions
Coordination Number
Each atom has the same number of nearest neighbor or touching atoms
APF
(volume of atoms in a unit cell)/(total unit cell volume)
FCC
Face Centered Cubic
FCC Geometry
Atoms located at each of the corners and the centers of all faces, total of four atoms
BCC
Body Centered Cubic
BCC Geometry
atoms located at all eight corners and a single atom the cube center, total of two atoms
HCP
Hexagonal Close Packed
HCP Geometry
Top and bottom faces of the unit cell consist of six atoms that form regular hexagons and surround a single atom at the cente
Vacancy
Vacant lattice site; one which is normally occupied but the atom is missing
Self-Interstitial
An atom from the crystal that is crowded into an interstitial site
Substitutional Defect
Solute or impurity atoms replace or
substitute for host atoms
Interstitial Defect
Impurity atoms fill the voids or
interstices among the host atoms
Atomic Size Factor
The atomic radii of the solute and solvent atoms must differ by no more than 15%
Crystal Structures
The crystal structures of solute and solvent must match
Electronegativity
The solute and solvent should have similar electronegativity. If the difference is too great, intermetallic compounds will form
Valences
Maximum solubility occurs when the solvent and solute have the same valency. Metals with lower valency will tend to dissolve metals with higher valency
Interstitial Solid Solutions
Solute atoms must be smaller than the pores in the solvent lattice
Solvent
represents the element or compound that is present in the greatest amount
Solute
element or compound present in minor concentration
Weight Percent
Weight of a particular element relative to the total alloy weight
Atom Percent
Based on the number
of moles of an element in relation
to the total moles of elements in the alloy
Dislocation
Linear or one-dimensional defect around which some of the atoms are misaligned
Screw Dislocations
Form by shear stress that is applied to produce the
Edge Dislocation
Magnitude and direction of the lattice distortion associated with a dislocation is expressed in terms of a Burgers vector.
Grain Boundaries
boundary separating two small grains or crystals having different orientations
Twin Boundaries
Special type of grain boundary across which there is a specific mirror lattice symmetry
Steady State Diffusion
Diffusion flux does not change with time
Concentration Gradient
(Ca-Cb)/(Xa-Xb) or dC/dx
D
Diffusion coefficient
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