Tellurium
(Te) - is added to steel to modify sulfide type inclusion
size, morphology and distribution. The resulting sulfide type
inclusions are finer and remain ellipsoidal in shape following
hot working, thereby improving transverse properties.
Temper (1) In heat treatment, reheating
hardened steel or hardened cast iron to some temperature below
the eutectoid temperature for the purpose of decreasing hardness
and increasing toughness. The process also is sometimes applied
to normalized steel. (2) In tool steels, temper is sometimes used,
but inadvisably, to denote carbon content. (3) In nonferrous alloys
and in some ferrous alloys (steels that cannot be hardened by
heat treatment), the hardness and strength produced by mechanical
or thermal treatment, or both, and characterized by a certain
structure, mechanical properties, or reduction in area during
cold working.
Temper
carbon Same as annealing
carbon.
Temper
color A thin, tightly adhering oxide skin that forms
when steel is tempered at a low temperature, or for a short time,
in air or a mildly oxidizing atmosphere. The color, which ranges
from straw to blue depending on the thickness of the oxide skin,
varies with both tempering time and temperature.
Tempered
martensite embrittlement Embrittlement
of ultrahigh-strength steels caused by tempering in the temperature
range of 205 to 400°C (400 to 750°F); also called 350°C
or 500°F embrittlement. Tempered martensite embrittlement
is thought to result from the combined effects of cementite precipitation
on prior-austenite grain boundaries or interlath boundaries and
the segregation of impurities at prior-austenite grain boundaries.
Temper
embrittlement Embrittlement
of alloy steels caused by holding within or cooling slowly through
a temperature range just below the transformation range. Embrittlement
is the result of the segregation at grain boundaries of impurities
such as arsenic, antimony, phosphorus, and tin; it is usually
manifested as an upward shift in ductile-to-brittle transition
by retempering above the critical temperature range, then cooling
rapidly.
Temper
Stressing - Quenching in water from the tempering temperature
to improve fatigue strength.
Tempering - A treatment consisting
of heating uniformly to some predetermined temperature under the
critical range, holding at that temperature a designated period
of time and cooling in air or liquid. This treatment is used to
produce one or more of the following end results: A) to soften
material for subsequent machining or cold working, B) to improve
ductility and relieve stresses resulting from prior treatment
or cold working, and C) to produce the desired mechanical properties
or structure in the second step of a double treatment.
Temperature - Degree of warmth or coldness in relation
to an arbitrary zero measured on one or more of accepted scales,
as Centigrade, Fahrenheit, etc.
Tensile
Strength - The maximum stress in uniaxial tension testing
which a material will withstand prior to fracture. The ultimate
tensile strength is calculated from the maximum load applied during
the test divided by the original cross-sectional area. Compare
with yield strength.
Tensile stress - Axial forces per unit area applied to
a body that tend to extend it.
Thermal
analysis A method for determining transformations in a metal
by noting the temperatures at which thermal arrests occur. These
arrests are manifested by changes in slope of the plotted of mechanically
traced heating and cooling curves. When such data are secured
under nearly equilibrium conditions of heating and cooling, the
method is commonly used for determining certain critical temperatures
required for the construction of equilibrium diagrams.
Thermal
barrier coating - A coating produced to present an insulating
barrier to a heat source and to protect the substrate.
Thermal
conductivity - The property of matter by which heat energy
is transmitted through particles in contact. For engineering purposes,
the amount of heat conducted through refractories is usually given
in Btu per hour for one square foot of area, for a temperature
difference of one degree Fahrenheit, and for a thickness of one
inch, Btu/hr·ft·F/in.
Thermal
Diffusion (TD) - A salt bath treatment at about 900°C
for high carbon tool steels. Produces a very hard layer of vanadium
carbide, typically .0002-.0003 thick. Also called Thermo-Reactive
Diffusion (TRD).
Thermal
electromotive force The electromotive force generated in
a circuit containing two dissimilar metals when one junction is
at a temperature different from that of the other. See also thermocouple.
Thermal
fatigue Fracture resulting from the presence of temperature
gradients that vary with time in such a manner as to produce cyclic
stresses in a structure. Failure resulting from rapid cycles of
alternate heating and cooling.
Thermal
shock Stress developed by rapid and uneven heating of a
material.
Thermal
spraying - A process in which coating material is heated and
accelerated from a spray torch towards the work piece. The deposited
material forms a coating on the surface.
Thermal
stresses Stresses in metal resulting from nonuniform temperature
distribution. Usually occurs during the cooling of a part.
Thermochemically
formed coatings - A painted, dipped or sprayed chromium oxide
based coating consolidated by repeated deposition and curing cycles
(about 500°C).
Thermochemical
treatment Heat treatment carried out in a medium suitably
chosen to produce a change in the chemical composition of the
object by exchange with the medium.
Thermocouple
A device for measuring temperatures, consisting of lengths of
two dissimilar metals or alloys that are electrically joined at
one end and connected to a voltage-measuring instrument at the
other end. When one junction is hotter than the other, a thermal
electromotive force is produced that is roughly proportional to
the difference in temperature between the hot and cold junctions.
Thermography
- An NDE technique in which the coating is flash heated and then
viewed with an infra red camera. "Hot spots" indicate
areas of poor bonding or greater coating thickness.
Thermomechanical
working A general term covering a variety of processes combining
controlled thermal and deformation treatments to obtain specific
properties. Same as thermal-mechanical treatment.
Three-quarters
hard A temper of nonferrous alloys
and some ferrous alloys characterized by tensile strength and
hardness about midway between those of half
hard and full hard
tempers.
Time quenching
A term used to describe a quench in which the cooling rate of
the part being quenched must be changed abruptly at some time
during the cooling cycle.
Time-temperature-transformation
(TTT) diagram See isothermal
transformation (IT) diagram.
Titanium
(Ti) - is added to boron steels because it combines with oxygen
and nitrogen, thus increasing the effectiveness of boron. Titanium,
as titanium nitride, also provides grain size control at elevated
temperatures in microalloy steels. In excess, titanium is detrimental
to machinability and internal cleanness.
Titanium
nitride (TiN) - Gold colored ceramic, typically applied as
a thin coating by either PVD or CVD. Very hard (3500Hv). Used
on cutting tools and forming tools and other surfaces requiring
wear resistance
Tolerance
- The permissible deviation of a dimension from the nominal or
desired value. Minimum clearance between mating parts.
Tool Steel
- Any high-carbon or alloy steel used to make a cutting tool
for machining and forming metals and for metal-casting dies.
Total carbon
The sum of the free and combined carbon (including carbon in
solution) in a ferrous alloy.
Total indicator
reading See preferred term total indicator variation.
Total indicator
variation The difference between the maximum and minimum
indicator readings during a checking cycle.
Toughness
The ability of a metal to absorb energy and deform plastically
before fracturing.
Trajectory
- The path a particle takes when its injected into a stream of
moving gas (or fluid). It is used in CFD to predict the path of
the metal powder used in the plasma spray gun analysis.
Transcrystalline
See transgranular.
Transferred
arc - In a plasma torch the plasma jet is emitted from the
torch and the current flows from the internal cathode to the internal
anode represented by the nozzle of the torch. When the jet is
carried to another anode with it being electrically favorable
to do so the current will then transfer to the second anode, usually
the work piece and the arc is said to be transferred.
Transferred Arc (Plasma) - The plasma arc which transfers
heat energy to the work piece (base material). This arc strikes
between the tungsten electrode (cathode) and the base material
(anode). The term Main Arc is also used in Plasma Transferred
Arc process (P.T.A. welding).
Transformation
hardening Heat treatment comprising austenitization followed
by cooling under conditions such that the austenite transforms
more or less completely into martensite and possibly into bainite.
Transformation-induced
plasticity A phenomenon, occurring chiefly in certain highly
alloyed steels that have been heat treated to produce metastable
austenite or metastable austenite plus martensite, whereby, on
subsequent deformation, part of the austenite undergoes strain-induced
transformation to martensite. Steels capable of transforming in
this manner, commonly referred to as TRIP steels, are highly plastic
after heat treatment, but exhibit a very high rate of strain hardening
and thus have high tensile and yield strengths after plastic deformation
at temperatures between about 20 and 500°C (70 and 930°F).
Cooling to -195°C (-320°F) may or may not be required
to complete the transformation to martensite. Tempering usually
is done following transformation.
Transformation
ranges Those ranges of temperature within which a phase
forms during heating and transforms during cooling. The two ranges
are distinct, sometimes overlapping but never coinciding. The
limiting temperatures of the ranges depend on the composition
of the alloy and on the rate of change of temperature, particularly
during cooling. See transformation
temperature.
Transformation
temperature The temperature at which a change in phase
occurs. The term is sometimes used to denote the limiting temperature
of a transformation range. The following symbols are used for
iron and steels.
Accm
In hypereutectoid steel, the temperature at which the solution
of cementite in austenite is completed during heating.
Ac1 The temperature at which austenite begins
to form during heating.
Ac3
The temperature at which transformation of ferrite to austenite
is completed during heating
Ac4
The temperature at which austenite transforms to delta ferrite
during heating.
A3cm,
Ae1, Ae3, Ae4 The temperature
of phase changes at equilibrium.
Arcm
In hypereutectoid steel, the temperature at which precipitation
of cementite starts during cooling.
Ar1
The temperature at which transformation of austenite to ferrite
or to ferrite plus cementite is completed during cooling.
Ar3
The temperature at which austenite begins to transform to
ferrite during cooling.
Ar4
The temperature at which delta ferrite transforms to austenite
during cooling.
Ar The
temperature at which transformation of austenite to pearlite
starts during cooling.
Mf
The temperature at which transformation of austenite to martensite
finishes during cooling.
Ms (or Ar) The temperature at which transformation
of austenite to martensite starts during cooling.
Note: All
these changes except the formation of martensite occur at lower
temperatures during cooling than during heating, and depend
on the rate of change of temperature.
Transgranular
Through or across crystals or grains. Also called intracrystalline
or transcrystalline.
Transgranular
cracking Cracking or fracturing that occurs through or across
a crystal or grain. Also called transcrystalline cracking. Contrast
with intergranular
cracking.
Transgranular
fracture Fracture through or across the crystals or grains
of a metal. Also called transcrystalline fracture or intracrystalline
fracture. Contrast with intergranular
fracture.
Transition
temperature (1) An arbitrarily defined temperature that
lies within the temperature range in which metal fracture characteristics
(as usually determined by tests of notched specimens) change rapidly,
such as from primarily fibrous (shear) to primarily crystalline
(cleavage) fracture. Commonly used definitions are transition
temperature for 50% cleavage fracture, 10 ft lbf transition
temperature, and transition temperature for half maximum energy.
(2) Sometimes used to denote an arbitrarily defined temperature
within a range in which the ductility changes rapidly with temperature.
Transmission
Electron Microscopy (TEM) - Applied to thin and thick film
analysis, it permits observation of smaller features such as microcolumnar
voids and patterns of dislocations in the bulk.
Transparent Electrical Conductors - Transparent conductive
oxide (TCO) films, such as indium trioxide (In2O3),
tin dioxide (SnO2), zinc oxide (ZnO) and an alloy
of indium oxide and tin oxide (ITO), have numerous applications
such as heaters on windows for defrosting, antistatic coatings
on display screens, electrodes on flat panel displays and electrochromic
devices, and electrodes on both flexible (resistive screen) and
rigid (capacitive screen) touch screens. Electrical resistivity
for the TCO films can vary from greater than 1,000 ohms per "square"
to less than 10 ohms per square with good optical transmission.
Trap - This condition applies to a wall entity during a
CFD analysis of a particulate two-phase flow. A particle touches
the wall entity, its momentum and energy are assumed to be completely
lost to the wall entity, while the mass is assumed lost to the
fluid.
TRD
(Thermo-Reactive Diffusion) - A salt bath treatment at about
900°C
for high carbon tool steels. Produces a very hard layer of vanadium
carbide, typically .0002-.0003 thick. Also called Thermal
Diffusion (TD).
TRIP steel
A commercial steel product exhibiting transformation-induced
plasticity.
Troostite
(obsolete) A previously unresolved rapidly etching fine
aggregate of carbide and ferrite produced either by tempering
martensite at low temperature or by quenching a steel at a rate
slower than the critical cooling rate. Preferred terminology for
the first product is tempered martensite; for the latter, fine
pearlite.
Tungsten
carbide - Metallic colored ceramic, often applied as a coating
by thermal spraying. With a Co or Ni binder. Used for high load
applications requiring extreme wear resistance.
Tungsten
disulphide - Dry lubricant coating - applied at ambient temperature.
Coating is 0.5 micron thick works at temperatures -273deg k to
650deg C. For use at high vacuum, cryogenic or high temperatures.
Extends bearing life. Prevents galling, fretting & seizing.
Can be applied to miniature ball races in assembled condition.
Developed by NASA for use in deep space. Used in plastics industry
as permanent release coating.
Turbulent
flow - Technical terminology for the type of flow which occurs
when the Reynolds Number exceeds 2000. In contrast to laminar
flow, turbulent flow can be described as an irregular and random-looking
motion.
Two-phase
- Particular type of analysis where two of the three phases (gas,
liquid and solid) are modeled together. The numerical equations
are modified to produce an interaction between the two phases.
