Mse Ch 5

Front 1

basal slip

Back 1

Deformation that occurs on the basal plane of HCP crystals as a result of dislocation motion

Front 2

Burgers circuit

Back 2

A circuit drawn around a dislocation through defect-free material that would normally close if there were no dislocation inside of the circuit

Front 3

Burgers vector (b)

Back 3

The vector that joins the end to the start of the Burger’s circuit. This is an invariant property of a dislocation

Front 4

critical resolved shear stress

Back 4

The shear stress resolved in the slip plane in the slip direction at which plastic deformation occurs

Front 5

dislocation

Back 5

A linear defect in a crystalline solid that is responsible for plastic deformation

Front 6

dislocation climb

Back 6

The motion of an edge dislocation that occurs when vacancies migrate to the edge of the extra half plane. This results in the dislocation being displaced to a parallel slip plane. This requires mass transport

Front 7

dislocation glide

Back 7

Motion of a dislocation on its slip plane (defined by the Burger’s vector and the unit tangent vector). This kind of dislocation motion does not involve mass transport

Front 8

edge dislocation

Back 8

A dislocation that is formed (figuratively) by the insertion of an extra half plane into an otherwise perfect region of a crystal

Front 9

flow stress

Back 9

Stress required to continue plastic deformation. The stress at which plastic deformation first occurs is a specific value of this and is referred to as the yield stress

Front 10

grain boundary

Back 10

Boundary that occurs when two crystals of arbitrary orientation to each other are joined along an arbitrary surface. This is a planar defect

Front 11

normal stress

Back 11

The force divided by the area normal to the force

Front 12

Petch-Hall equation

Back 12

Equation that provides the relationship between the grain size and the yield stress. The yield stress increases with decreasing grain size according to this

Front 13

plastic deformation

Back 13

Deformation that is permanent; for example, a metal part that has been permanently bent is said to have undergone this

Front 14

precipitation hardening

Back 14

Hardening or strengthening of an alloy by the presence of a fine, uniformly distributed precipitate

Front 15

Schmid's law

Back 15

The equation that relates the orientation of a crystal and the normal stress to the shear stress at which plastic deformation occurs

Front 16

screw dislocation

Back 16

A dislocation that may be formed by making a cut in a crystal and displacing the top half of the cut region relative to the bottom half in a direction parallel to the cut. The Burger’s vector of this is parallel to the dislocation line

Front 17

shear stress

Back 17

Force divided by the area of the plane in which the force acts. These are responsible for the motion of dislocations

Front 18

slip direction

Back 18

The direction in which atoms are displaced across the slip plane when a dislocation passes over the slip plane. This is parallel to the Burger’s vector of the dislocation responsible for the slip being considered

Front 19

slip plane

Back 19

The plane on which a dislocation moves by glide. It is defined by the Burger’s vector and the unit tangent vector

Front 20

slip system

Back 20

Any combination of slip direction and slip plane on which deformation can occur

Front 21

stacking fault

Back 21

A variation in the normal stacking sequences of close-packed planes. For example, in FCC crystals the normal stacking sequence is ABCABC..., and if in some region of the crystal the stacking is ABCBCABC..., that region is said to contain this

Front 22

strain hardening

Back 22

Hardening that occurs as a result of deforming a metal. During this, dislocations are generated and the high dislocation density makes it difficult for other dislocations to move

Front 23

stress

Back 23

Force per unit area

Front 24

surface tension

Back 24

Energy per unit area associated with internal or external surfaces. It has units of energy/area, which is equivalent to force/length

Front 25

tilt boundary

Back 25

A boundary composed of edge dislocations of the same sign stacked vertically above one another. As a result of all of the extra half planes being in one portion of the crystal, a tilt is created

Front 26

twin

Back 26

A portion of a crystal in which all of the atoms are in mirror-image positions compared with atoms in the bulk of the crystal

Front 27

twist boundary

Back 27

A boundary that is composed of a grid of screw dislocations of like sign on the same plane. As a result of the displacements around the grid, a twist is created

Front 28

unit tangent vector

Back 28

Vector that is locally tangent to the direction of a dislocation at the point of interest

Front 29

void

Back 29

A volumetric defect in which there is no matter

Front 30

yield stress

Back 30

The stress at which deformation becomes permanent in a tensile test