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Catégorie :Category: mViewer GX Creator Lua TI-Nspire
Auteur Author: sergiodurazo33
Type : Classeur 3.6
Page(s) : 17
Taille Size: 2.69 Mo MB
Mis en ligne Uploaded: 12/09/2019 - 19:14:18
Uploadeur Uploader: sergiodurazo33 (Profil)
Téléchargements Downloads: 1
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a2317906

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Repaso Parcial 1


Teoria

Which statement is false? The homogeneous nucleation requires a higher undercooling than
heterogeneous because it occurs spontaneously.

When it is said that for a phase change to occur, there has to be an energetic engine and a route
through which to carry out the process, it is understood that… There must be a large enough energy
source to “overcome the energy barrier” of the proposed change and a thermodynamic disequilibrium.

Rapid solidification processing is used to produce exceptionally fine secondary dendrite arm spacing, in
these cases, the mechanical properties such as tensile stress and elongation are expected to: Both
increase

When accelerating the cooling rate during solidification, the secondary dendrite arms spacing (SDAS) is
reduced, why? Because the dendritic formation requires diffusion, and shorter solidification times
reduce the mass flow distances

In a two-phase material consisting of a matrix and secondary particles that exist in thermodynamic
equilibrium, large particles tend to integrate small ones (large particles “eat” small ones). Why is this
tendency. Because the energy invested in surface tension is reduced

An Al-4wt% Cu alloy is homogenized at 550 °C and then quenched into water. When aged at 150°C, the
ally reaches peak hardness in 100 hr; when aged at 130 °C the same effect is reached in 1000 hr. How
much time would it take to reach peak hardness when aged at 170°C? 12.3; range (9.3-15.3)

Select all the variables which define a given thermodynamic state. Concentration, pressure, temperature

Excellent combinations of hardness, strength, and toughness are obtained from bainite. One heat
treatment facility austenitized a eutectoid steel at 750°C, quenched and held the material at 250°C for 1
hour, and finally quenched to room temperature. Was the required bainitic structure obtained? No, the
full bainitic structure was not obtained



Typical Al alloys resist creep, fatigue and wear __________ than low alloy steels. Worst

Hardenability of steels can be measured with a Vickers quench test. False

When adding Cr to low alloy steels the tendency to retain austenite during hardening by quenching…
increases

Choose the answer containing the possible thermodynamic states of a substance. Stable, unstable,
metastable, neutral or indifferent

Typical Cu alloys have a corrosion resistance that is _________ than that of low alloy steels, and ______
than high alloy steels. Higher / lower

Typical Cu alloy have a ______ atomic structure. Fcc
Repaso Parcial 1


Match the column of “typical heat treatments” for carbon steels with their “purposes”.

Get high hardness and toughness simultaneously in martensite. Tempering

Reach maximum hardness in steels. Quenching

Soften metals which produce precipitates on slow cooling. Homogenizing

Relieve residual stresses. Process annealing

Hardening solid solutions by precipitation. Ageing

Improve machinability of steels with medium and high carbon. Spheroidizing

Recrystallized cold worked microstructures. Annealing

Refine grain size. Normalizing

Maximize strength and toughness in medium carbon steels. Austempering

Harden only the surface of a low carbon steel. Carburizing and quenching



When adding Ni to low alloy steels the tendency to retain austenite during hardening by quenching…
increases

Typical Al alloys are reinforced, when adding Si, by _________. Dispersion strengthening

Mark all those properties for which precious metals are normally selected. Aesthetics, corrosion
resistance, electrical conductivity, electrochemical activity

Typical Cu alloys are reinforced, when adding Cr, by ______. Dispersion strengthening

Typical Al alloys show a ______ effect of cold working on strength and conductivity. Moderate

The Ms and Mf temperatures of carbon steels depend on the C content, and tend to increase with
increasing C content. False

Addling Mn to typical Al alloys improves the ________. Castability

Typical Al alloys have a corrosion resistance that is ________ than that of low alloy steels, and _______
than high alloy steels. Higher / lower

The more severe the quench media, the larger the critical diameter of a given steel. True

Martensite of steels is a metastable solid solution with a body-centered cubic structure. False

Typical Cu alloys show a ______ effect of cold working on strength and conductivity. Strong

When adding Ni to low alloy steels the toughness of the material… increases

When adding Cr to low alloy steels the allowable service temperature… increases

Adding Fe to typically Al alloys improves the ________. Strength
Repaso Parcial 1


Which of the following represents the main property which make refractory metals suitable for a given
application? High melting temperature

Typical Cu alloys resist creep, fatigue and wear __________ than alloy steels. Worst

When adding Ni to low alloy steels the critical isothermal transformation time… does not change

Bainite is a finer microstructure than pearlite, and thus harder and tougher. True

Adding Mg to typical Al alloys improves the _______. Strength

When adding Ni to low alloy steels the softening during tempering… does not change

When adding Cr to low alloy steels the critical isothermal transformation time… increases

Malleable cast iron is the result of heat-treating a white cast iron which typically has a carbon equivalent
of 3 to 3.4%. True

The eutectoid pearlite structure is formed faster than the eutectic ledeburite structures. False

The critical diameter of a steel is the one that produces 50% ferrite at the center of properly quenched
cylindrical rod. False

When adding Ni to low alloy steels the allowable service temperature… increases

When adding Cr to low alloy steels the toughness of the material… decreases

Potential hardness of a low alloy steel is a sole function of its [A] content: and the maximum
hardenability potential corresponds to a content of [B]%. A=Carbon, B=
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Diagrams…
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A – Liquid

B – Peritectic

C – Alpha

D – Eutectic

E – Eta/Theta

F – Theta/Eta

G – None

H – Eutectic

I – Beta
Repaso Parcial 1

Archive contentsContenu de l'archive

Action(s) SizeTaille FileFichier
1.64 Ko KB readme.txt
1.12 Mo MB QuimicaAvanzada/11-17.tns
1.62 Mo MB QuimicaAvanzada/01-10.tns

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