Exam 1

From actual and previous exam

Van der Waals

Dipole-dipole interaction

The near neighbor distances between anion and cations in a ceramic

are established by the coordination number

_ generally, have low packing densities when compared with other materials

polymers

During elastic deformation, a metal experiences

bond stretching

Plastic deformation in metallic alloys is the result of

Dislocation motion

Young's Modulus characterizes what property of a material

elasticity

The percent of elongation of a material at failure defines its

ductility

Edge and screw dislocations differ in what way?

Angles between Burgers' vector and line direction

A solid solution wherein relatively small solute atoms occupy the "open space" between the solvent atoms is referred to as

Interstitial solid solution

Elastic deformation is

recoverable

If a material's measured properties are different in different directions, the materials is said to be:

anisotropic

The atomic packing factor (APF) for hexagonal closed-packed (HCP) crystal structure is 0.74. What is it for Face Center Cubic (FCC)?

0.74

The coordination number refers to the:

number of nearest neighboring atoms in a crystal

a type of grain boundary that has a 'mirror image' symmetry about the boundary is referred to as

Twin boundary

Dislocations are type of linear defects

True

One requirement for complete solubility is that the crystal structure of the two elements can't be the same as each other

False

The atomic packing factor can never be 1.0 (100%)

True

Carbon is added to iron to make steel a stronger material

True

Yield strength

Max stress a material can handle before it permanently deforms

Proportional limit

stress at which transition between linear and non-linear behavior

Toughness

energy absorbed by the material until it fails represented by the area under stress strain curve

Unit cell

the smallest repeating unit in a crystal structure

Amorphous

nanocrystalline material with nonuniform structure

Substitutional defect

a point defect where an atom of similar size replaces that of host element

Modulus of Resilience

ability of a material to absorb energy during elastic deformation represented by area under stress strain curve up to yield point

If the grain size of a material decreases, its surface area:

increases

When plasticly deformed, strain hardening causes metals to become:

harder

Steel

is an iron-carbon alloy

Ceramics are ______ dense that most metals and alloys

less

image of a stress vs strain graph used for reference: the data could have been obtained from a

uniaxial tensile test

image of a stress vs strain graph used for reference: yield strength can be obtained looking at the graph at which point?

the point at which linear transitions to a curve line

image of a stress vs strain graph used for reference: necking can be observed at what point on the graph

The highest point displayed on the graph is necking

image of a stress vs strain graph used for reference: dislocations begin to move when this strain is exceeded?

The corresponding stress(x-axis) to yield strength

The total area under the stress vs strain curve represents

estimate of toughness

Ionic Bonds

transfer of electrons from one elemental atom to another. Occurs between + and - ions and usually has a large difference in electronegativity(

covalent bonds

sharing of electrons between specific atoms. Bonds involve valance electrons and normally come from s and p orbitals. Same electronegitivity.

metallic bonds

mass sharing of electrons between several atoms, electrons delocalize to from electron cloud.

As elasticity increases what happens to melting temperature

it increases

As elasticity decreases what happens to thermal expansion

it increases

characteristics of ceramics(ionic and covalent):

high melting temp, large elasticity, and small thermal expansion

Metal characteristics (Metallic):

mid melting temp, mid elasticity, and mid thermal expansion

Polymer characteristics(covalent and secondary):

low melting temp, small elasticity, and large thermal expansion

crystalline materials have

atoms arranged in periodic, 3D arrays. Typically metals, ceramics, and some polymers.

nanocrystalline ‘amorphous’ materials

atoms have no periodic arrangement

Atomic Packing Factor of BCC

0.68

Atomic Packing Factor of FCC and HCP

0.74

in general density’s of metals, ceramics, and polymers are ordered how

p metals>p ceramics>p polymers

what are the factors that effect crystal structure

relative size of ions and maintenance of charge neutrality

Conditions for substitutional solid

1. difference in atomic radius <15%

2. similar electronegativities

3. same crystal structure

4. equal valance electron

edge dislocation

extra half plane of atoms inserted in a crystal structure perpendicular to dislocation line

screw dislocation

spiral planar ramp resulting from shear deformation parallel to dislocation line

Yielding is a _______ phenomenon

shear