Chapter 4 defects in solids Flashcards

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1
Q

why are defects important

A

defects have a huge impact on the various properties of materials

  • defects are responsible for color and price of a diamond
  • forging a metal tool introduces defects and increases the strength of the tool
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2
Q

defects can be introduced or removed during ________

A

Processing

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3
Q

point defects

A

are lattice defects of zero dimensionality, i.e., they do not possess lattice structure in any dimension. Typical point defects are impurity atoms in a pure metal, vacancies, and self-interstitials.

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4
Q

vacancies

A

is a type of point defect in a crystal where an atom is missing from one of the lattice sites.

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5
Q

interstitial defect

A

is a type of point crystallographic defect where an atom of the same or of a different type, occupies a normally unoccupied site in the crystal structure.

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6
Q

point defects in metals

A
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7
Q

equilibrium concentration

A

Equilibrium is when the rate of the forward reaction equals the rate of the reverse reaction. All reactant and product concentrations are constant at equilibrium.

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8
Q

Boltzmann’s constant

A
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9
Q

activation energy

A

the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction.

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10
Q

measuring activation energy

A
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11
Q

estimating vacancy concentration

A
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12
Q

observing vacancy ( continued )

A
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13
Q

impurities

A

are foreign atoms that replace some of the atoms making up the solid or that squeeze into the interstices

atoms that are different from the host

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14
Q

a homogeneous material

A

or system has the same properties at every point

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15
Q

solids with impurities

A
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16
Q

substitutional impurity

A

An atom or ion which is not normally found in a solid, but which resides at the position where an atom or ion would ordinarily be located in the lattice structure and replaces it.

17
Q

three types of point defects

A

Vacancy - in crystal an atom is missing from one of the lattice sites (point defect)

Interstitial - in crystal an atom of the same or different type occupies a normally unoccupied site in the lattice

Substitutional- same as interstitial but a different type of atom resulting in strain

18
Q

*quick reference *

imperfections in metals

A
19
Q

W Hume Rothery rules

A

are a set of basic rules that describe the conditions under which an element could dissolve in a metal, forming a solid solution.

20
Q

solubility

imperfections in metals

A
21
Q

Dislocations ( dislocation lines )

A

are linear defects. the interatomic bonds are significantly distorted only in the immediate vicinity of the dislocation line. this area is called the dislocation core.

22
Q

burgers vector

A
23
Q

edge dislocation

A

is a defect where an extra half-plane of atoms is introduced midway through the crystal( burger vector is perpendicular to dislocation line)

24
Q

Screw dislocation

A

a spiral planar ramp is inserted ( burger vector is parallel to dislocation line)

25
Q

mixed / partial dislocations

A
26
Q

where do dislocations come from

A

the number of dislocations in a material is expressed as the dislocation density ( the total dislocation length per unit volume or the number of dislocations intersecting a unit area )

27
Q

plastic deformation

A

is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces.

28
Q

dislocations and crystal structures/ plastic deformation

A
29
Q

grain boundaries

A

is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are 2D defects in the crystal structure and tend to decrease the electrical and thermal conductivity of the material.

30
Q

solidification

A

result of casting of molten material

31
Q

steps of solidification

A
32
Q

grain boundaries properties

A
33
Q

interaction between grain boundaries and dislocation

A
34
Q

bulk or volume defects

A

Three-dimensional macroscopic defects. They generally occur on a much larger scale than the microscopic defects.

-these include cracks, pores, foreign inclusions, and other phases.

35
Q

Summary of this chapter

A