Matsci exam 2

Question 1

A force applied so as to cause or tend to cause two adjacent parts of the same body to slide relative to each other in a direction parallel to their plane of contact

Answer 1

shear

Question 2

The instantaneous load applied to a specimen divided by its cross-sectional area before any deformation.

Answer 2

engineering stress σ

Question 3

The change in gauge length of a specimen (in the direction of an applied stress) divided by its original gauge length.

Answer 3

engineering strain (E)

Question 4

The ratio of stress to strain when deformation is totally elastic; also a measure of the stiffness of a material.

Answer 4

modulus of elasticity

Question 5

Deformation that is nonpermanent—that is, totally recovered upon release of an applied stress.

Answer 5

elastic deformation:

Question 6

Nonpermanent deformation recovered or regained upon release of a mechanical stress

Answer 6

elastic recovery

Question 7

Time-dependent elastic (nonpermanent) deformation.

Answer 7

anelastic deformation

Question 8

The onset of plastic deformation.

Answer 8

yielding

Question 9

The point on a stress-strain curve at which the straight-line proportionality between stress and strain ceases.

Answer 9

proportional limit

Question 10

The stress required to produce a very slight yet specified amount of plastic strain; a strain offset of 0.002 is commonly used

Answer 10

yield strength

Question 11

The maximum engineering stress, in tension, that may be sustained without fracture. Often termed ultimate (tensile) strength.

Answer 11

tensile strength

Question 12

A measure of a material’s ability to undergo appreciable plastic deformation before fracture; it may be expressed as percent elongation (%EL) or percent reduction in area (%RA) from a tensile test.

Answer 12

ductility

Question 13

The capacity of a material to absorb energy when it is elastically deformed.

Answer 13

resilience

Question 14

A mechanical characteristic that may be expressed in three contexts: (1) the measure of a material’s resistance to fracture when a crack (or other stress-concentrating defect) is present; (2) the ability of a material to absorb energy and plastically deform before fracturing; and (3) the total area under the material’s tensile engineering stress-strain curve taken to fracture.

Answer 14

toughness

Question 15

The instantaneous applied load divided by the instantaneous cross-sectional area of a specimen

Answer 15

true stress

Question 16

The natural logarithm of the ratio of instantaneous gauge length to original gauge length of a specimen being deformed by a uniaxial force.

Answer 16

true strain

Question 17

Stress at fracture from a bend (or flexure) test.

Answer 17

flexural strength

Question 18

A polymeric material that may experience large and reversible elastic deformations.

Answer 18

elastomer

Question 19

A type of deformation exhibiting the mechanical characteristics of viscous flow and elastic deformation.

Answer 19

viscoelasticity

Question 20

For viscoelastic polymers, the time-dependent modulus of elasticity. It is determined from stress relaxation measurements as the ratio of stress (taken at some time after the load application—normally 10 s) to strain

Answer 20

relaxation modulus

Question 21

The measure of a material’s resistance to deformation by surface indentation or by abrasion.

Answer 21

hardness

Question 22

Product of the calculated stress level (on the basis of estimated maximum load) and a design factor (which has a value greater than unity). Used to protect against unanticipated failure.

Answer 22

design stress

Question 23

A stress used for design purposes; for ductile metals, it is the yield strength divided by a factor of safety

Answer 23

safe stress

Question 24

Plastic deformation as the result of dislocation motion; also, the shear displacement of two adjacent planes of atoms.

Answer 24

slip

Question 25

The total dislocation length per unit volume of material; alternatively, the number of dislocations that intersect a unit area of a random surface section.

Answer 25

dislocation density

Question 26

Slight displacements of atoms relative to their normal lattice positions, normally imposed by crystalline defects such as dislocations, and interstitial and impurity atoms.

Answer 26

lattice strain

Question 27

The combination of a crystallographic plane and, within that plane, a crystallographic direction along which slip (i.e., dislocation motion) occurs

Answer 27

slip system

Question 28

An applied tensile or compressive stress resolved into a shear component along a specific plane and direction within that plane.

Answer 28

resolved shear stress

Question 29

The shear stress, resolved within a slip plane and direction, required to initiate slip.

Answer 29

critical resolved shear stress

Question 30

Hardening and strengthening of metals that result from alloying in which a solid solution is formed. The presence of impurity atoms restricts dislocation mobility.

Answer 30

solid-solution strengthening

Question 31

The increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.

Answer 31

strain hardening

Question 32

The plastic deformation of a metal at a temperature below that at which it recrystallizes.

Answer 32

cold working

Question 33

The relief of some of the internal strain energy of a previously cold-worked metal, usually by heat treatment.

Answer 33

recovery

Question 34

The formation of a new set of strain-free grains within a previously cold-worked material; normally, an annealing heat treatment is necessary.

Answer 34

recrystallization

Question 35

For a particular alloy, the minimum temperature at which complete recrystallization occurs within approximately 1 h.

Answer 35

recrystallization temperature

Question 36

The increase in average grain size of a polycrystalline material; for most materials, an elevated-temperature heat treatment is necessary.

Answer 36

grain growth

Question 37

A forming technique used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of a tensile force applied on the exit side.

Answer 37

drawing (metals)

Question 38

A nonreversible chemical reaction involving sulfur or another suitable agent in which crosslinks are formed between molecular chains in rubber materials. The rubber's modulus of elasticity and strength are enhanced.

Answer 38

vulcanization

Question 39

A mode of fracture attended by extensive gross plastic deformation.

Answer 39

ductile fracture

Question 40

Fracture that occurs by rapid crack propagation and without appreciable macroscopic deformation.

Answer 40

brittle fracture

Question 41

Fracture of polycrystalline materials by crack propagation through the grains.

Answer 41

transgranular fracture

Question 42

Fracture of polycrystalline materials by crack propagation along grain boundaries.

Answer 42

intergranular fracture

Question 43

A small flaw (internal or surface) or a structural discontinuity at which an applied tensile stress will be amplified and from which cracks may propagate

Answer 43

stress raiser

Question 44

The measure of a material's resistance to fracture when a crack is present.

Answer 44

fracture toughness

Question 45

The condition, in which, for tensile loading, there is zero strain in a direction perpendicular to both the stress axis and the direction of crack propagation; this condition is found in thick plates, and the zero-strain direction is perpendicular to the plate surface.

Answer 45

plane strain:

Question 46

one of two tests that may be used to measure the impact energy or notch toughness of a standard notched specimen. An impact blow is imparted to the specimen by means of a weighted pendulum. (not done in class)

Answer 46

Charpy test:

Question 47

One of two tests that may be used to measure the impact energy of a standard notched specimen. An impact blow is imparted to the specimen by a weighted pendulum.

Answer 47

Izod test

Question 48

A measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading. Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material.

Answer 48

impact energy (notch toughness)

Question 49

The transition from ductile to brittle behavior with a decrease in temperature exhibited by some low-strength steel (BCC) alloys; the temperature range over which the transition occurs is determined by Charpy and Izod impact tests.

Answer 49

ductile-to-brittle transition

Question 50

For fatigue, the maximum stress amplitude level below which a material can endure an essentially infinite number of stress cycles and not fail.

Answer 50

fatigue limit

Question 51

Hardening of the outer surface of a steel component by a carburizing or nitriding process; used to improve wear and fatigue resistance.

Answer 51

case hardening

Question 52

A type of fatigue failure in which the cyclic stresses are introduced by fluctuating thermal stresses

Answer 52

thermal fatigue

Question 53

A type of failure that results from the simultaneous action of a cyclic stress and chemical attack

Answer 53

corrosion fatigue

Question 54

The time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.

Answer 54

creep

Question 55

The maximum concentration of solute that may be added without forming a new phase.

Answer 55

solubility limit

Question 56

A homogeneous portion of a system that has uniform physical and chemical characteristics.

Answer 56

phase

Question 57

A thermodynamic quantity that is a function of both the internal energy and entropy (or randomness) of a system. At equilibrium, the _______ is at a minimum.

Answer 57

free energy

Question 58

A nonequilibrium state that may persist for a very long time.

Answer 58

metastable

Question 59

Having the same structure. In the phase diagram sense, ________ means having the same crystal structure or complete solid solubility for all compositions.

Answer 59

isomorphous

Question 60

A horizontal line constructed across a two-phase region of a binary phase diagram; its intersections with the phase boundaries on either end represent the equilibrium compositions of the respective phases at the temperature in question.

Answer 60

tie line

Question 61

A mathematical expression by which the relative phase amounts in a two-phase alloy at equilibrium may be computed,

Answer 61

lever rule

Question 62

The locus of points on a phase diagram representing the limit of solid solubility as a function of temperature.

Answer 62

solvus line

Question 63

On a binary phase diagram, the line or boundary separating liquid- and liquid + solid-phase regions. For an alloy, the liquidus temperature is the temperature at which a solid phase first forms under conditions of equilibrium cooling

Answer 63

liquidus line

Question 64

On a phase diagram, the locus of points at which solidification is complete upon equilibrium cooling, or at which melting begins upon equilibrium heating

Answer 64

solidus line

Question 65

A reaction in which, upon cooling, a liquid phase transforms isothermally and reversibly into two intimately 2 solid phases.

Answer 65

eutectic reaction

Question 66

A two-phase microstructure (2 solids) resulting from the solidification (cooling) of a liquid having the _______ composition; the phases exist as lamellae that alternate with one another.

Answer 66

eutectic structure

Question 67

An element of the microstructure that has an identifiable and characteristic structure. It may consist of more than one phase, such as with pearlite.

Answer 67

microconstituent

Question 68

A phase that exists in addition to the eutectic structure.

Answer 68

primary phase

Question 69

A solid solution that exists over a composition range extending to either composition extreme of a binary phase diagram.

Answer 69

terminal solid solution

Question 70

A solid solution or phase having a composition range that does not extend to either of the pure components of the system

Answer 70

intermediate solid solution

Question 71

A compound of two metals that has a distinct chemical formula. On a phase diagram it appears as an intermediate phase that exists over a very narrow range of compositions

Answer 71

intermetallic compound:

Question 72

A reaction in which, upon cooling, one solid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed.

Answer 72

eutectoid reaction

Question 73

A reaction in which, upon cooling, a solid and a liquid phase transform isothermally and reversibly to a solid phase having a different composition.

Answer 73

peritectic reaction

Question 74

A transformation of one phase to another of the same composition.

Answer 74

congruent transformation

Question 75

For a system at equilibrium, an equation that expresses the relationship between the number of phases present and the number of externally controllable variables

Answer 75

Gibbs phase rule

Question 76

Ceramic oxide materials composed of both divalent and trivalent cations (e.g., Fe2+ and Fe3+), some of which are ferrimagnetic.

Answer 76

ferrite (iron)

Question 77

Face-centered cubic iron; also iron and steel alloys that have the FCC crystal structure.

Answer 77

austenite

Question 78

Iron carbide

Answer 78

cementite

Question 79

A two-phase microstructure found in some steels and cast irons; it results from the transformation of austenite of eutectoid composition and consists of alternating layers (or lamellae) of α-ferrite and cementite.

Answer 79

pearlite

Question 80

For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition.

Answer 80

hypoeutectoid alloy

Question 81

Primary ferrite that exists in addition to pearlite for hypoeutectoid steels.

Answer 81

proeutectoid ferrite

Question 82

For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.

Answer 82

hypereutectoid alloy

Question 83

Primary cementite that exists in addition to pearlite for hypereutectoid steels.

Answer 83

proeutectoid cementite

Question 84

The initial stage in a phase transformation. It is evidenced by the formation of small particles of the new phase that are capable of growing.

Answer 84

nucleation

Question 85

Cooling to below a phase transition temperature without the occurrence of the transformation.

Answer 85

supercooling

Question 86

Heating to above a phase transition temperature without the occurrence of the transformation.

Answer 86

superheating

Question 87

Pearlite for which the alternating ferrite and cementite layers are relatively thick.

Answer 87

coarse pearlite

Question 88

Pearlite in which the alternating ferrite and cementite layers are relatively thin.

Answer 88

fine pearlite

Question 89

An austenitic transformation product found in some steels and cast irons. It forms at temperatures between those at which pearlite and martensite transformations occur. The microstructure consists of α-ferrite and a fine dispersion of cementite.

Answer 89

bainite

Question 90

Microstructure found in steel alloys consisting of spherelike cementite particles within an α-ferrite matrix. It is produced by an appropriate elevated-temperature heat treatment of pearlite, bainite, or martensite and is relatively soft.

Answer 90

spheroidite

Question 91

The microstructural product resulting from a tempering heat treatment of a martensitic steel. The microstructure consists of extremely small and uniformly dispersed cementite particles embedded within a continuous α-ferrite matrix. Toughness and ductility are enhanced significantly by tempering.

Answer 91

tempered martensite

Question 92

A metastable iron phase supersaturated in carbon that is the product of a diffusionless (athermal) transformation from austenite.

Answer 92

martensite

Question 93

A reaction that is not thermally activated, and usually diffusionless, as with the martensitic transformation. Normally, the transformation takes place with great speed (i.e., is independent of time), and the extent of reaction depends on temperature.

Answer 93

athermal transformation

Question 94

the process used to form a solid solution by dissolving precipitate particles. Often, the solid solution is supersaturated and metastable at ambient conditions as a result of rapid cooling from an elevated temperature.

Answer 94

solution heat treatment

Question 95

A heat treatment used to precipitate a new phase from a supersaturated solid solution. For precipitation hardening, it is termed artificial aging.

Answer 95

precipitation heat treatment

Question 96

During precipitation hardening, aging beyond the point at which strength and hardness are at their maxima.

Answer 96

overaging

Question 96

For precipitation hardening, aging at room temperature.

Answer 96

natural aging

Question 97

For precipitation hardening, aging above room temperature.

Answer 97

artificial aging