structure of crystals and diffraction exam 3

interstitial

in metals, the self-_______ concentrations is negligible in metals regardless of temperature

disordered

in a ____ solid solution, the probability of a site being occupied is proportional to the at% alloying composition

anti-site

can consider chemical disordering as an increase in _____ defects

decreases

a decrease in chemical ordering ____ the intensity of superlattice peaks

schottky defect

Charge-compensating cation and anion vacancies.

frenkel defect

Charge neutral vacancy-interstitial pair

opposite

When point defects have _____ charges, their electrostatic attraction will favor them being in neighboring sites.

T

a dislocation characterized by b and t can only move in slip planes containing both b and t (T/F)

burgers vector

Describes the magnitude and direction of displacement of the crystal lattice across the dislocation, remains constant

tangent vector

unit vector that varies along curvilinear dislocations and is tangent to every point along the dislocation line; it is constant for straight (segments of ) dislocations

perpendicular

in an edge dislocation, b is ____ to t (their dot product=0 and cross product = glide plane normal)

parallel

in a screw dislocation, b is ____ to t (their dot product=|b|l)

positive

is this a positive or negative edge dislocation?

conservative

GLIDE or SLIP of dislocations is a ______ motion, there is a conservation of lattice sites

non-conservative

CLIMB of dislocations is a ____ motion, requires destruction or creation of lattice sites for motion to occur.

positive

is this a positive or negative climb?

negative

is this a positive or negative climb?

T

only dislocations with edge character (edge and mixed) can climb, not screw (T/F)

F

slip planes with low planar atomic density is preferred (T/F)

<111>

what is the likely burgers vector in a BCC crystal?

<100>

what is the likely burgers vector in a primitive cubic crystal?

<110>

what is the likely burgers vector in an FCC crystal?

is not

partial/imperfect dislocation has a burgers vector that ___ a lattice translation

shortest

in an alloy, the likely burgers vector is the ____ distance between two lattice sites of same element

shockley

Planar Dissociation reaction of unit dislocations produce a ribbon of stacking fault (SF) bound by pairs of _____ partials that are favorable regarding elastic line energy reduction

F

high stacking fault energy makes it difficult to cross-slip (T/F)

vacancy

A _____ can be described as a vacant lattice site that normally is occupied by an atom when the perfect reference state is considered

lower

vacancies have ___ mobility than self-interstitials

independent

enthalpy of formation for vacancies is (independent/dependent) of temperature

increases

Does the enthalpy for vacancy formation increase or decrease with an increase in the melting temperature?

smaller

the enthalpy of migration for self interstitials is typically much _____ than that for vacancies

dislocation, disclination

_____ line defects involve translation of one part of a crystal with respect to another, _____ line defects involve rotation of one part of a crystal with respect to another

glissile, sessile

dislocations that can move easily by slip are _____ and those that have difficulty are ____ (they cannot move by slip)

parallel, perpendicular

an edge dislocation moves _____ in the direction of shear, a screw dislocation moves _____ in the direction of shear

frank, sessile

The ____ loop is a planar dislocation that results from a condensation of point defects in a close-packed crystal, which is a partial dislocation and is ______ (glissile/sessile) because it cannot move by slip.

paralell

The direction of dislocation motion, or slip direction, is _____ to b

T

Preferred slip systems are in close-packed directions on close-packed planes (T/F)

cross-slip, screw

_______ is a mechanism that occurs when a dislocation encounters an obstacle and switches slip plane, only ____(screw/edge) dislocations can do this.

highest

Dislocations lying in a slip system with the ____ Schmid factor will be the first to move when a force is applied

raises

The effect of interactions between the elastic fields of several dislocations within vicinity of each other ___ the external stress needed to move a dislocation.

forest, decreases

One dislocation “threads through” the slip plane of another dislocation, what type of dislocation is this? Once it has been cut by another moving dislocation, the mobility of both dislocations ______

frank-read source

A mechanism that requires a glissile dislocation to be pinned at two ends that bows into an arc under applied stress, increasing curvature as stress increases, until it reaches a critical point and simply generates a new loop surrounding the pinned points.

arrhenius

Law that describes how the number of vacancies in equilibrium is exponentially related to an increase in temperature, independent of enthalpy of formation

dot, cross

when determining alternative slip plane for a cross slip, you find another plane normal for a close packed plane for which its ___ product with b = 0. to find the subsequent tangent vector, you take the ____ product of b and plane normal.

cross

given b and t, you take the ___ product to find the slip plane

plane normal, b

Cos1= cosine between loading direction and ____

cos2= cosine between loading direction and ____

F

Glide motion of the screw dislocation causes displacement by its Burgers vector for specific regions of a crystal, while edge dislocation climb motion does not cause any displacements in crystals (T/F)

F

A dislocation is a line defect that is always straight and typically aligned along crystallographic directions associated with a low value of the elastic modulus (T/F)

a/6

if a burgers vector direction is multiplied by a/2, what would its subsequent shockley partial be multiplied by?

burgers

elastic line energy or self-energy is proportional to the square of the magnitude of the ____ vector for dislocations

‘

in kroger-vink notation, how do you show charge relative to normal ion charge on site if its negative?

^o

in kroger-vink notation, how do you show charge relative to normal ion charge on site if its positive?

charge and mass

in a kroger-vink notation equation, what two things must be balanced?