test 2 vocab Flashcards
(152 cards)
1
Q
modulus of elasticity (E):
A
The ratio of stress to strain when deformation is totally elastic; also a measure of the stiffness of a material.
2
Q
elastic deformation:
A
Deformation that is nonpermanent—that is, totally recovered upon release of an applied stress.
3
Q
plastic deformation:
A
Deformation that is permanent or nonrecoverable after release of the applied load. It is accompanied by permanent atomic displacements.
4
Q
yielding:
A
The onset of plastic deformation. (begins to deform indefinetly)
5
Q
proportional limit:
A
The point on a stress-strain curve at which the straight-line proportionality between stress and strain ceases. (point where the line starts to curve over)
6
Q
yield strength (σy):
A
The stress required to produce a very slight yet specified amount of plastic strain; a strain offset of 0.002 is commonly used.
7
Q
tensile strength (TS):
A
The maximum engineering stress, in tension, that may be sustained without fracture. Often termed ultimate (tensile) strength.
8
Q
ductility:
A
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 tes
9
Q
resilience:
A
The capacity of a material to absorb energy when it is elastically deformed.
10
Q
toughness:
A
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.
11
Q
engineering stress:
A
The instantaneous load applied to a specimen divided by its cross-sectional area before any deformation.
12
Q
engineering strain:
A
The change in gauge length of a specimen (in the direction of an applied stress) divided by its original gauge length. (pushing out or change of length or width)
13
Q
shear:
A
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.(pushes sideways at the top)
14
Q
anelastic deformation:
A
Time-dependent elastic (nonpermanent) deformation.
15
Q
Poisson’s ratio (ν):
A
For elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress.
16
Q
true stress (σT):
A
The instantaneous applied load divided by the instantaneous cross-sectional area of a specimen.
17
Q
true strain (εT):
A
The natural logarithm of the ratio of instantaneous gauge length to original gauge length of a specimen being deformed by a uniaxial force.
18
Q
hardness:
A
The measure of a material’s resistance to deformation by surface indentation or by abrasion.
19
Q
design stress (σd):
A
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.
20
Q
safe stress (σw):
A
A stress used for design purposes; for ductile metals, it is the yield strength divided by a factor of safety.
21
Q
slip:
A
Plastic deformation as the result of dislocation motion; also, the shear displacement of two adjacent planes of atoms.
22
Q
dislocation density:
A
The total dislocation length per unit volume of material; alternatively, the number of dislocations that intersect a unit area of a random surface section.
23
Q
lattice strain:
A
Slight displacements of atoms relative to their normal lattice positions, normally imposed by crystalline defects such as dislocations, and interstitial and impurity atoms.
24
Q
slip system:
A
The combination of a crystallographic plane and, within that plane, a crystallographic direction along which slip (i.e., dislocation motion) occurs.
({} and [])
25
resolved shear stress:
An applied tensile or compressive stress resolved into a shear component along a specific plane and direction within that plane.
26
critical resolved shear stress (τcrss):
The shear stress, resolved within a slip plane and direction, required to initiate slip.
27
solid-solution strengthening:
Hardening and strengthening of metals that result from alloying in which a solid solution is formed. The presence of impurity atoms restricts dislocation mobility.
28
strain hardening:
The increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.
29
cold working:
The plastic deformation of a metal at a temperature below that at which it recrystallizes.
30
recovery:
The relief of some of the internal strain energy of a previously cold-worked metal, usually by heat treatment.
31
recrystallization:
The formation of a new set of strain-free grains within a previously cold-worked material; normally, an annealing heat treatment is necessary.
32
recrystallization temperature:
For a particular alloy, the minimum temperature at which complete recrystallization occurs within approximately 1 h.
33
grain growth:
The increase in average grain size of a polycrystalline material; for most materials, an elevated-temperature heat treatment is necessary.
34
ductile fracture:
A mode of fracture attended by extensive gross plastic deformation.
35
brittle fracture:
Fracture that occurs by rapid crack propagation and without appreciable macroscopic deformation.
36
transgranular fracture:
Fracture of polycrystalline materials by crack propagation through the grains.
37
intergranular fracture:
Fracture of polycrystalline materials by crack propagation along grain boundaries.
38
fracture mechanics:
A technique of fracture analysis used to determine the stress level at which preexisting cracks of known size will propagate, leading to fracture.
39
stress raiser:
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.
40
fracture toughness (Kc):
The measure of a material's resistance to fracture when a crack is present.
41
plane strain:
The condition, important in fracture mechanical analyses, 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.
42
plane strain fracture toughness (KIc):
For the condition of plane strain, the measure of a material's resistance to fracture when a crack is present.
43
Charpy test:
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.
44
Izod test:
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.
45
impact energy (notch toughness):
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.
46
ductile-to-brittle transition:
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.
47
fatigue:
Failure, at relatively low stress levels, of structures that are subjected to fluctuating and cyclic stresses.
48
fatigue limit:
For fatigue, the maximum stress amplitude level below which a material can endure an essentially infinite number of stress cycles and not fail.
49
fatigue strength:
The maximum stress level that a material can sustain without failing, for some specified number of cycles.
50
fatigue life (Nf):
The total number of stress cycles that cause a fatigue failure at some specified stress amplitude.
51
case hardening:
Hardening of the outer surface (or case) of a steel component by a carburizing or nitriding process; used to improve wear and fatigue resistance.
52
thermal fatigue:
A type of fatigue failure in which the cyclic stresses are introduced by fluctuating thermal stresses.
53
corrosion fatigue:
A type of failure that results from the simultaneous action of a cyclic stress and chemical attack.
54
creep:
creep: The time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.
55
component:
A chemical constituent (element or compound) of an alloy that may be used to specify its composition.
56
system:
Two meanings are possible: (1) a specific body of material being considered, and (2) a series of possible alloys consisting of the same components.
57
solubility limit:
The maximum concentration of solute that may be added without forming a new phase.
58
phase:
A homogeneous portion of a system that has uniform physical and chemical characteristics.
59
equilibrium (phase):
The state of a system in which the phase characteristics remain constant over indefinite time periods. At equilibrium the free energy is a minimum.
60
free energy:
A thermodynamic quantity that is a function of both the internal energy and entropy (or randomness) of a system. At equilibrium, the free energy is at a minimum.
61
phase equilibrium:
See equilibrium (phase).
62
metastable:
A nonequilibrium state that may persist for a very long time.
63
phase diagram:
A graphical representation of the relationships among environmental constraints (e.g., temperature and sometimes pressure), composition, and regions of phase stability, typically under conditions of equilibrium.
64
isomorphous:
Having the same structure. In the phase diagram sense, isomorphicity means having the same crystal structure or complete solid solubility for all compositions.
65
tie line:
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.
66
lever rule:
A mathematical expression by which the relative phase amounts in a two-phase alloy at equilibrium may be computed. ( amount of phase amounts at equilibrium)
67
solvus line:
The locus of points on a phase diagram representing the limit of solid solubility as a function of temperature.
68
solidus line:
On a phase diagram, the locus of points at which solidification is complete upon equilibrium cooling, or at which melting begins upon equilibrium heating.
(Curves back or forward at the front and end of table)
69
liquidus line:
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.
70
eutectic reaction:
A reaction in which, upon cooling, a liquid phase transforms isothermally and reversibly into two intimately mixed solid phases.
71
eutectic structure:
A two-phase microstructure resulting from the solidification of a liquid having the eutectic composition; the phases exist as lamellae that alternate with one another.
72
eutectic phase:
One of the two phases found in the eutectic structure.
73
primary phase:
A phase that exists in addition to the eutectic structure.
74
microconstituent:
An element of the microstructure that has an identifiable and characteristic structure. It may consist of more than one phase, such as with pearlite.
(has structure to its arrangement)
75
terminal solid solution:
A solid solution that exists over a composition range extending to either composition extreme of a binary phase diagram. ( the end of a phase that exists at a certain temperature)
76
intermediate solid solution:
A solid solution or phase having a composition range that does not extend to either of the pure components of the system.
77
intermetallic compound:
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.
78
eutectoid reaction:
A reaction in which, upon cooling, one solid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed.
79
peritectic reaction:
A reaction in which, upon cooling, a solid and a liquid phase transform isothermally and reversibly to a solid phase having a different composition.
(liquid is above solid)
80
congruent transformation:
A transformation of one phase to another of the same composition.
81
Gibbs phase rule:
For a system at equilibrium, an equation that expresses the relationship between the number of phases present and the number of externally controllable variables.
82
ferrite (ceramic):
Ceramic oxide materials composed of both divalent and trivalent cations (e.g., Fe2+ and Fe3+), some of which are ferrimagnetic.
83
austenite:
Face-centered cubic iron; also iron and steel alloys that have the FCC crystal structure.
84
cementite:
Iron carbide (Fe3C).
85
pearlite:
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
86
hypoeutectoid alloy:
For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition.
87
proeutectoid ferrite:
Primary ferrite that exists in addition to pearlite for hypoeutectoid steels.
88
hypereutectoid alloy:
For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.
89
proeutectoid cementite:
Primary cementite that exists in addition to pearlite for hypereutectoid steels.
90
transformation rate:
The reciprocal of the time necessary for a reaction to proceed halfway to its completion.
91
phase transformation:
A change in the number and/or character of the phases that constitute the microstructure of an alloy.
92
phase transformation:
A change in the number and/or character of the phases that constitute the microstructure of an alloy.
93
nucleation:
The initial stage in a phase transformation. It is evidenced by the formation of small particles (nuclei) of the new phase that are capable of growing.
(start of phase transformation)
94
growth (particle):
During a phase transformation and subsequent to nucleation, the increase in size of a particle of a new phase.
95
free energy:
A thermodynamic quantity that is a function of both the internal energy and entropy (or randomness) of a system. At equilibrium, the free energy is at a minimum.
96
kinetics:
The study of reaction rates and the factors that affect them.
97
thermally activated transformation:
A reaction that depends on atomic thermal fluctuations; the atoms having energies greater than an activation energy spontaneously react or transform.
98
supercooling:
Cooling to below a phase transition temperature without the occurrence of the transformation.
99
superheating:
Heating to above a phase transition temperature without the occurrence of the transformation.
100
sothermal transformation (T-T-T) diagram:
A plot of temperature versus the logarithm of time for a steel alloy of definite composition. Used to determine when transformations begin and end for an isothermal (constant temperature) heat treatment of a previously austenitized alloy.
(wavy diagram)
101
coarse pearlite:
Pearlite for which the alternating ferrite and cementite layers are relatively thick.
102
fine pearlite:
Pearlite in which the alternating ferrite and cementite layers are relatively thin.
103
bainite:
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.
104
spheroidite:
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.
105
martensite:
A metastable iron phase supersaturated in carbon that is the product of a diffusionless (athermal) transformation from austenite.
106
athermal transformation:
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.
107
plain carbon steel:
A ferrous alloy in which carbon is the prime alloying element.
108
alloy steel:
A ferrous (or iron-based) alloy that contains appreciable concentrations of alloying elements (other than C and residual amounts of Mn, Si, S, and P). These alloying elements are usually added to improve mechanical and corrosion-resistance properties.
109
continuous-cooling transformation (CCT) diagram:
A plot of temperature versus the logarithm of time for a steel alloy of definite composition. Used to indicate when transformations occur as the initially austenitized material is continuously cooled at a specified rate; in addition, the final microstructure and mechanical characteristics may be predicted.
110
tempered martensite:
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.
111
ferrous alloy:
A metal alloy for which iron is the prime constituent.
112
plain carbon steel:
A ferrous alloy in which carbon is the prime alloying element.
113
alloy steel:
A ferrous (or iron-based) alloy that contains appreciable concentrations of alloying elements (other than C and residual amounts of Mn, Si, S, and P). These alloying elements are usually added to improve mechanical and corrosion-resistance properties.
114
high-strength, low-alloy (HSLA) steel:
Relatively strong, low-carbon steels, with less than about 10 wt% total of alloying elements.
115
stainless steel:
A steel alloy that is highly resistant to corrosion in a variety of environments. The predominant alloying element is chromium, which must be present in a concentration of at least 11 wt%; other alloy additions, including nickel and molybdenum, are also possible.
116
cast iron:
Generically, a ferrous alloy, the carbon content of which is greater than the maximum solubility in austenite at the eutectic temperature. Most commercial cast irons contain between 3.0 and 4.5 wt% C and between 1 and 3 wt% Si.
117
gray cast iron:
A cast iron alloyed with silicon in which the graphite exists in the form of flakes. A fractured surface appears gray.
118
ductile iron:
A cast iron alloyed with silicon and a small concentration of magnesium and/or cerium and in which the free graphite exists in nodular form. Sometimes called nodular iron.
119
white cast iron:
A low-silicon and very brittle cast iron in which the carbon is in combined form as cementite; a fractured surface appears white.
120
malleable cast iron:
White cast iron that has been heat-treated to convert the cementite into graphite clusters; a relatively ductile cast iron.
121
compacted graphite iron:
A cast iron alloyed with silicon and a small amount of magnesium, cerium, or other additives, in which the graphite exists as wormlike particles.
122
wrought alloy:
A metal alloy that is relatively ductile and amenable to hot working or cold working during fabrication.
123
brass:
A copper-rich copper-zinc alloy.
124
bronze:
A copper-rich copper-tin alloy; aluminum, silicon, and nickel bronzes are also possible.
125
temper designation:
A letter-digit code used to designate the mechanical and/or thermal treatment to which a metal alloy has been subjected.
126
specific strength:
The ratio of tensile strength to specific gravity for a material.
127
nonferrous alloys:
A metal alloy of which iron is not the prime constituent.
128
drawing (metals):
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
129
extrusion:
A forming technique by which a material is forced, by compression, through a die orifice.
130
rolling:
A metal-forming operation that reduces the thickness of sheet stock; elongated shapes may be fashioned using grooved circular rolls.
131
forging:
Mechanical forming of a metal by heating and hammering.
132
cold working:
The plastic deformation of a metal at a temperature below that at which it recrystallizes.
133
hot working:
Any metal-forming operation performed above a metal's recrystallization temperature.
134
powder metallurgy (P/M):
The fabrication of metal pieces having intricate and precise shapes by the compaction of metal powders, followed by a densification heat treatment.
135
welding:
A technique for joining metals in which actual melting of the pieces to be joined occurs in the vicinity of the bond. A filler metal may be used to facilitate the process.
136
annealing:
A generic term used to denote a heat treatment in which the microstructure and, consequently, the properties of a material are altered. Annealing frequently refers to a heat treatment whereby a previously cold-worked metal is softened by allowing it to recrystallize.
137
process annealing:
Annealing of previously cold-worked products (commonly steel alloys in sheet or wire form) below the lower critical (eutectoid) temperature.
138
stress relief:
A heat treatment for the removal of residual stresses.
139
lower critical temperature:
For a steel alloy, the temperature below which, under equilibrium conditions, all austenite has transformed into ferrite and cementite phases.
140
upper critical temperature:
For a steel alloy, the minimum temperature above which, under equilibrium conditions, only austenite is present.
141
normalizing:
For ferrous alloys, austenitizing above the upper critical temperature, then cooling in air. The objective of this heat treatment is to enhance toughness by refining the grain size.
142
austenitizing:
Forming austenite by heating a ferrous alloy above its upper critical temperature—to within the austenite phase region from the phase diagram.
143
full annealing:
For ferrous alloys, austenitizing, followed by cooling slowly to room temperature.
144
spheroidizing:
For steels, a heat treatment normally carried out at a temperature just below the eutectoid in which the spheroidite microstructure is produced.
145
hardenability:
A measure of the depth to which a specific ferrous alloy may be hardened by the formation of martensite upon quenching from a temperature above the upper critical temperature.
146
Jominy end-quench test:
A standardized laboratory test used to assess the hardenability of ferrous alloys.
147
precipitation hardening:
Hardening and strengthening of a metal alloy by extremely small and uniformly dispersed particles that precipitate from a supersaturated solid solution; sometimes also called age hardening.
148
solution heat treatment:
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.
149
precipitation heat treatment:
A heat treatment used to precipitate a new phase from a supersaturated solid solution. For precipitation hardening, it is termed artificial aging.
150
overaging:
During precipitation hardening, aging beyond the point at which strength and hardness are at their maxima.
151
natural aging:
For precipitation hardening, aging at room temperature.
152
artificial aging:
For precipitation hardening, aging above room temperature.
