MATSE 259 Exam 1 PSU With Complete
Solutions
Elastic Modulus (e)
measure of stiffness, or a material's resistance to elastic deformation ... slope of elastic portion of
stress-strain curve
Crystalline Materials
small group of atoms that are repeated by translation to form 3-D arrangements
Antisotropic
properties that vary with direction. Ex: E(edge) isn't equal to E(diagonal)
Polycrystal
properties that may or may not vary with direction
Isotropic
the grains are randomly orientated
The Three Crystal Structures
Body Centered Cubic (BCC), Face Centered Cubic (FCC), Hexagonal Centered Prism (HCP)
Co-ordination Numbers
number of atoms in a crystal lattice touching a given atom
Co-ordination Numbers for each Structure
BCC = 8 FCC = 12 HCP = 12
Polymorphism
same atoms can have more than one crystal structure
Close Packed Structures
atoms in close touch as many as possible.
Which crystal structures are tightly packed vs ones that aren't?
BCC is NOT packed compared to HCP and FCC (most packed)
, FCC layer structure
A, B, C repeat
HCP layer structure
A, B repeat
Linear Density
Linear Density = # of atoms/ unit length of the vector
Planar Density
density across a plane; # of atoms in the plane/area of plane
What are the three type of point defects?
Vacancies, Interstitial Atoms, Substitutional Atoms
Vacancies
very important during diffusion!! Basically open spots in the plane
Substitutional Atoms
these make solid solutions if atoms can bond together must follow of one these rules;
Interstitional
makes solid solutions; if the alloying atom is very small it'll sit in between small crevices of the plane.
Usually happens with H,C,O,N.
Edge Dislocation
extra plane of atoms inserted into the crystal
Burgers Vector
measure of lattice distortion, perpendicular to distortion line
Screw Dislocation
material is twisted so some atoms are above and below each other
Solutions
Elastic Modulus (e)
measure of stiffness, or a material's resistance to elastic deformation ... slope of elastic portion of
stress-strain curve
Crystalline Materials
small group of atoms that are repeated by translation to form 3-D arrangements
Antisotropic
properties that vary with direction. Ex: E(edge) isn't equal to E(diagonal)
Polycrystal
properties that may or may not vary with direction
Isotropic
the grains are randomly orientated
The Three Crystal Structures
Body Centered Cubic (BCC), Face Centered Cubic (FCC), Hexagonal Centered Prism (HCP)
Co-ordination Numbers
number of atoms in a crystal lattice touching a given atom
Co-ordination Numbers for each Structure
BCC = 8 FCC = 12 HCP = 12
Polymorphism
same atoms can have more than one crystal structure
Close Packed Structures
atoms in close touch as many as possible.
Which crystal structures are tightly packed vs ones that aren't?
BCC is NOT packed compared to HCP and FCC (most packed)
, FCC layer structure
A, B, C repeat
HCP layer structure
A, B repeat
Linear Density
Linear Density = # of atoms/ unit length of the vector
Planar Density
density across a plane; # of atoms in the plane/area of plane
What are the three type of point defects?
Vacancies, Interstitial Atoms, Substitutional Atoms
Vacancies
very important during diffusion!! Basically open spots in the plane
Substitutional Atoms
these make solid solutions if atoms can bond together must follow of one these rules;
Interstitional
makes solid solutions; if the alloying atom is very small it'll sit in between small crevices of the plane.
Usually happens with H,C,O,N.
Edge Dislocation
extra plane of atoms inserted into the crystal
Burgers Vector
measure of lattice distortion, perpendicular to distortion line
Screw Dislocation
material is twisted so some atoms are above and below each other
