Chp.3 Defects

Question 1

What is a vacancy defect?

Answer 1

A normally occupied lattice site from which an atom or ion is missing.

Question 2

What is a self-interstitial defect?

Answer 2

This is when an atom is in a crammed spot surrounded by other atoms in an interstitial spot.
Interstitial- A small void space that normally goes unoccupied.

Question 3

What is an impurity atom?

Answer 3

This is when a crystal structure has an atom from a different element than what it is made up of.

Question 4

Equilibrium # of vacancies Equation

Answer 4

Nv = N^(-Qv/KT)
N = # of atomic sites
Qv = energy required for a vacancy J/mol or eV/atom
T = absolute temperature in Kelvin
K = gas or Boltzmann’s constant 1.38E-23 (J/atom)K or 8.62E-5 (eV/atom)K

Question 5

What is an imperfection?

Answer 5

An Imperfection is a deviation from a crystals atomic/molecular order and/or continuity.

Question 6

What is a point defect?

Answer 6

A point defect is crystalline defect associated at one or several atomic sites.

Question 7

What is an alloy?

Answer 7

An alloy is a metallic substance composed of two or more elements.

Question 8

What is a solid solution?

Answer 8

A homogeneous crystalline phase that contains two or more chemical species. Both substitutional and interstitial solid solutions are possible.

Question 9

What is a solute?

Answer 9

One component or element of a solution present in a minor concentration. It is dissolved in the solvent.

Question 10

What is a solvent?

Answer 10

The component of a solution present in the greatest amount. It is the component that dissolves a solute.

Question 11

What is a substitutional solid solution?

Answer 11

A solid solution in which the solute atoms replace or substitute for the host atoms.

Question 12

What is an interstitial solid solution?

Answer 12

A solid solution in which relatively small solute atoms occupy interstitial positions between the solvent or host atoms.

Question 13

Computation of weight% for two-element alloy and atom % of one element in alloy (n instead of m)

Answer 13

C1 = (m1)/(m1+m2) * 100

Question 14

Calculate the number of moles of an element

Answer 14

nm1 = (m’1/A1)
m’1 = mass in grams
A1 = Atomic weight for element

Question 15

What does C mean?

Answer 15

C is the relative weight % for an element in an alloy

Question 16

What does C’ mean?

Answer 16

C’ is the atom % for an element in an alloy

Question 17

What is A and Rho?

Answer 17

A stands for atomic weight and Rho stands for density

Question 18

What is an Edge dislocation?

Answer 18

A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers vector is perpendicular to the dislocation line.

Question 19

What is a Screw dislocation?

Answer 19

A linear crystalline defect associated with the lattice distortion created when normally parallel planes are joined together to form a helical ramp. The Burgers vector is parallel to the dislocation line.

Question 20

What is a dislocation line?

Answer 20

The line that extends along the end of the extra half-plane of atoms for an edge dislocation and along the center of the spiral of a screw dislocation.

Question 21

What is a Burgers vector?

Answer 21

A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.

Question 22

What is an external surface?

Answer 22

An external surface is a boundary on the surface of a material where surface atoms are not bonded to the maximum number of nearest neighbors.

Question 23

What is Ferromagnetic domain wall?

Answer 23

A ferromagnetic domain wall is a boundary that separates regions having different directions of magnetization in ferromagnetic and ferrimagnetic materials.

Question 24

What is a Grain boundary?

Answer 24

A grain boundary separates two grains or crystals having two different crystallographic orientations and can be described in terms of dislocation arrays.

Question 25

What is a phase boundary?

Answer 25

Phase boundaries exist in multiphase materials where a different phase exists on each side of the boundary. Each phase has distinctive physical and/or chemical characteristics.

Question 26

What is a twin boundary?

Answer 26

A twin boundary is a grain boundary in which atoms on one of the boundary's sides are located in mirror-image positions to the atoms on the boundary's other side.

Question 27

What is the Grain size?

Answer 27

The grain size is defined as the average grain diameter as determined from a random cross section.

Question 28

What is the linear intercept method for grain size?

Answer 28

The linear intercept method of grain-size determination involves counting numbers of grain boundaries that intersect with a series of straight test lines.

Question 29

What is the comparison method for grain size?

Answer 29

The comparison method of measuring grain size compares grain structures of a sample with standardized charts devised by the American Society for Testing and Materials (ASTM).