SoM Final Exam
This material has a cellular structure consisting of a solid metal (frequently aluminum) with gas-filled pores comprising a large portion of the volume.
Metal Foam
Why did people turn to iron if it is softer than bronze?
More plentiful
Would you expect a 2024-O aluminum alloy to have the same properties 2024-H alloy? Explain.
No, because although they are the same physical make up, the processing is different and therefore both will have different properties.
Label the 3 stages of creep that occur before rupture on the figure shown.
Primary Secondary Tertiary
Impact energy
The energy required to fracture a standard specimen when the load is applied suddenly.
Strain rate
The rate at which strain develops in or is applied to a material.
ductile to brittle transition temperature
The temperature below which a material behaves in a brittle manner in an impact test; it also depends on the strain rate.
Heat Affected Zone (HAZ)
The volume of material adjacent to a weld that is heated during the welding process above some critical temperature at which a change in the structure, such as grain growth or recrystallization, occurs.
Cold working cannot be used as a strengthening mechanism for materials that are going to be subjected to high temperatures during their use. Why?
This is true because annealing reverses the properties of cold working.
Ceramics normally have poor toughness, even if they display high strength, because they have virtually no ductility. These materials show both poor tensile toughness and poor impact toughness. (True, False)
True
Heating water to the boiling point breaks the van der Waals bonds and changes water to steam, but breaking the covalent bonds requires much higher temperatures. (True, False)
True
High powered magnets are manufactured through a process called sintering. (True, False)
True
Metamaterials are materials that are engineered to have a property that is not found in nature. (True, False)
True
Repeated temperature change encourages failure by thermal fatigue. (True, False)
True
The best way to decrease the time required for diffusions is to use higher temperatures or to make the diffusion distances small as possible. (True, False)
True
Thermal conductivity of most ceramics is low. (True, False)
True
Transfer of heat through ceramics occurs through lattice vibrations. (True, False)
True
Self-Healing Concrete
Uses bacteria
Given the following electron configurations classify the element as reactive or non-reactive. a) 1s2 2s2 2p6 3s2 3p6 b) 1s2 2s2 2p6 3s1
a) 1s2 2s2 2p6 3s2 3p6 - Non-Reactive b) 1s2 2s2 2p6 3s1 - Reactive
Which is the best conductor of electricity? a) Copper b) Aluminum Oxide c) PVC d) Gold
a) Copper
The three stage of annealing are: a) Recovery, Recrystallization, Grain Growth b) Strengthening, Working, Recovery c) Recovery, Rehabilitation, Grain Growth
a) Recovery, Recrystallization, Grain Growth
Classify the following materials as a polymer, metal, ceramic, or composite: a) Tungsten carbide b) Bike tire c) Cement d) Concrete e) Iron f) Fiberglass g) Aluminum Foil h) PVC
a) Tungsten carbide - Ceramic b) Bike tire - Polymer c) Cement - Ceramic d) Concrete - Composite e) Iron - Metal f) Fiberglass - Composite g) Aluminum Foil - Metal h) PVC - Polymer
Which of the following are conditions for unlimited solubility? (Circle all that apply?) The atoms or ions must... a) be similar in size. b) both be metals. c) have the same crystal structure. d) have the same valence. e) have similar melting temperatures. f) have approximately the same electronegativity.
a) be similar in size. c) have the same crystal structure. d) have the same valence. f) have approximately the same electronegativity.
Which of the following statements is ALWAYS true? Corrosion is the process where: a) electrons are transferred from one element to another. b) oxygen reacts with metals. c) water is present. d) electrons are transferred from a metal to a non-metal.
a) electrons are transferred from one element to another.
The generic reaction M → M^n- + ne^- represents a reaction that occurs at an ___________.
anode
A 0.4% carbon steel is slowly heated from room temperature to an elevated temperature. From the iron-iron carbide phase diagram, the temperature at which a single-phase solid solution is formed is most nearly: a) 727 ºC b) 830 ºC c) 912 ºC d) 1500 ºC
b) 830 ºC
Thermal conductivity is a) A measure of how changes size with a change in temperature. b) A measure of how fast heat will be conducted through a material. c) A measure of the ability of a material to conduct thermal energy relative to its ability to store thermal energy. d) The energy required to change the temperature of 1 kg of a material by 1ºC.
b) A measure of how fast heat will be conducted through a material.
These materials have good electrical and thermal conductivities, relatively high strength, high stiffness, ductility or formability, and shock resistance. These materials are particularly useful for structural or load-bearing applications. (Choose one) a) Polymer b) Metal c) Composite d) Semiconductors
b) Metal
Which is the best conductor of heat? a) Aluminum b) Silver c) Gold d) Zinc
b) Silver
The metal oxide formed will be protective if the P-B ratio is a) less than one. b) between one and two. c) greater than two.
b) between one and two.
The tensile test gives us all but which of the following material properties for a ductile material? a) modulus of elasticity b) hardness c) yield strength d) tensile strength
b) hardness
Hardenability may be defined as a) resistance to indentation b) the hardness attained for a specific cooling rate c) another measure of strength d) rate of increased hardness
b) the hardness attained for a specific cooling rate
______________ is when a metallic rod is pulled through a die to produce a wire or fiber. _____________ is when a material is pushed through a die to form products of uniform cross-sections. a. Extrusion, Drawing b. Drawing, Extrusion c. Forcing, Extrusion d. Drawing, Forcing
b. Drawing, Extrusion
Artificial joints are made of materials that are ___________ with the human body.
bio-compatible
Which of the following characteristics describes martensite? I. High ductility II. Formed by quenching austenite III. High Hardness a) I only b) I and II c) II and III d) I and III
c) II and III
The three basic steps encountered during precipitation hardening are; a) Solid-Solution treatment, Cooling, Age b) Heating, Quenching, Aging c) Solution Treatment, Quench, Age
c) Solution Treatment, Quench, Age
Corrosion of metals includes all but which of the following: a) uniform b) selective leaching c) combustion d) pitting
c) combustion
A way to form compressive stresses on the surface of glass is to heat the glass just below a specific temperature then let the glass cool more quickly on the surface than the center. This process is known as ________________. a) annealing b) equal heat exchange treatment c) tempering d) rapid surface cooling treatment
c) tempering
In Fick's first law the J is the ________, D is the __________ and dc/dx is the _________. a. concentration gradient, flux, diffusivity coefficient b. flux, concentration gradient, diffusivity coefficient c. flux, diffusivity coefficient, concentration gradient d. diffusivity coefficient, flux, concentration gradient
c. flux, diffusivity coefficient, concentration gradient.
Ceramics are poor in tension, but strong in ___________.
compression
Time dependent permanent deformation under a constant load or constant stress is known as _________.
creep
This material is generally an inorganic nonmetallic material, does not conduct heat well and must be heated to very high temperatures before melting. Also this material is very strong and hard, but also very brittle. (Choose one) a) Polymer b) Metal c) Composite d) Ceramic
d) Ceramic
Which of the following processes can increase the deformation resistance of metals? I. Annealing II. Hot-working III. Adding alloying elements IV. Hardening a) I and II b) I and IV c) II and III d) III and IV
d) III and IV
If steel (0.76 wt% carbon) is annealed by very slow cooling from 800º C to ambient temperature, its microstructure will consist almost entirely of: a) bainite b)austenite c) martensite d) pearlite
d) pearlite
An iron alloy contains 3.5% carbon by weight. In what phase is the alloy at 900º C? a) Liquid b) γ + liquid c) α + carbide d) γ austenite and carbide
d) γ austenite and carbide
Plain carbon steel is harder than pure iron because the addition of carbon impedes __________ motion.
dislocation
In simple _____________ alloys, small particles of one phase that is usually strong and hard, are introduced into a second phase that is weaker, put more ductile.
dispersion strengthening
Galvanic corrosion occurs when two ________________ come in contact.
dissimilar metals
Electroactive polymers change shape with an ______________ is applied to it.
electric charge
Piezo electric material produce ____________ when mechanically stressed.
electricity
Metal rubber can be used to conduct __________.
electricity.
Thermal energy is transferred by free ____________ and lattice __________.
electrons, vibrations
Toughness is how much __________ can be absorbed without breaking.
energy
Alloying steel makes it stronger, but it loses _________.
flexibility
Materials with bonding energy also have ________ strength and _______ melting temperature.
high, high
Deforming of materials above the recrystallization temperature is referred to as _____ working. Conducting shaping or deformation of materials at a temperature below the recrystallization temperature is referred to it as _______ working.
hot, cold
Aerogels are very good thermal __________.
inductors
Steel is basically an alloy between ________ and ___________.
iron, carbon
Aluminum is hard to process because it is strongly bonded to ___________ in its natural state.
oxygen
Plastics break down in sunlight through ______________.
photodegradation
Metal A is attached to metal B. If metal A loses electrons so to prevent metal B from corroding, then metal A is a _____________ anode.
sacrificial
Amorphous materials are different from crystalline materials because they only have ____________ range order.
short
Equilibrium Solidification occurs if the cooling rate is ________ enough that the atoms have enough time to diffuse.
slow
When a metal is cold worked, the ___________ increases and the ____________ decreases.
strength, ductility
Sintering is the high _____________ and/or high _____________ treatment that causes particles to join, gradually reducing the volume of pore space between them.
temperature, pressure
The equation σthermal = αEΔT is used to determine __________________ of a material.
thermal stress
Poisson's ratio (v) is the ratio of ___________ strain over ____________ strain.
transverse, axial
______ is the primary contributor to corrosion on automobiles.
Salt
______________ strengthening is caused by increased resistance to dislocation motion and is a reason why brass is stronger than copper.
Solid solution
Stainless steel
Steel that contains at least 11% Cr.
Indicate which property/process is most often associated with cold working and which is most often associated with hot working? Write HOT or COLD next to each. Strain hardening Large deformations High surface quality Oxide film Part shrinkage Accurate dimensional control Multiple steps No heating
Strain hardening - Cold Large deformations - Hot High surface quality - Cold Oxide film - Hot Part shrinkage - Hot Accurate dimensional control - Cold Multiple steps - Cold No heating - Cold
Why are age hardened metals not used in high temperature applications?
Strength may decrease because the precipitates grow too large, become incoherent, and are too few in number.
Strain hardening
Strengthening of a material by increasing the number of dislocations by deformation.
Uranium... (Choose all that apply) a) is radioactive. b) is exploited for its nuclear properties. c) slowly decays by emitting alpha particles. An alpha particle consists of 2 neutrons bound together with 2 protons. d) is found, in nature, mostly as uranium-238, uranium-235.
(All of them) a) is radioactive. b) is exploited for its nuclear properties. c) slowly decays by emitting alpha particles. An alpha particle consists of 2 neutrons bound together with 2 protons. d) is found, in nature, mostly as uranium-238, uranium-235.
List 4 ways that a metal can be protected from corrosion.
-Galvanizing -Cathodic Protection -Alloying -Protective Coating
Name 2 material properties (not ambient temperature or applied stress) that increase the creep resistance of a material.
-Low ductility -High strength
How much carbon does the following plain carbon steel alloy contain? 1040 Steel
0.4% Carbon
We would like to obtain a hardness of HRC 60 in a quenched steel. Which of the steels listed on the Jominey graph are appropriate for this task?
1060 (#2) at ≈ 75 ºC/sec 1060 (#8) at ≈ 125 ºC/sec
Graphene is electrically conductive because each carbon atom is only bonded to __________ other carbon atoms, whereas, each carbon atom in diamond is bonded to 4 other carbon atoms.
3
Temper designation
A letter and/or number used to describe the processing of an alloy.
Dislocation
A line imperfection in a crystalline material.
Recrystallization
A medium temperature annealing heat treatment designed to eliminate all of the effects of the strain hardening produced during cold working.
Schottky defect
A point defect in ionically bonded materials. In order to maintain a neutral charge, a cation and anion vacancies must form.
Interstitial
A point defect produced when an atom is placed into the crystal at a site that is normally not a lattice point.
Substitutional
A point defect produced when an atom is removed from a regular lattice point and replace with a foreign atom.
Wrought alloy
Alloys that are shaped by a deformation process.
If Aluminum and Tin were placed in electrical contact, which metal would be oxidized?
Aluminum
Vacancy
An atom or an ion missing from its regular crystallographic site.
Impact load
Application of stress at a high strain rate.
Amorphous Fullerene and Bucky balls are made of what element?
Carbon
Strain hardening is normally not a consideration in ceramics. Why?
Ceramics are brittle and it would break the material.
____________ refers to the net flux of any species, such as ions, atoms, electrons, holes, molecules.
Diffusion
What are the two modes of fracture? Give an example of a material that, under normal circumstances, undergoes that particular mode of fracture.
Ductile - Steel, Brittle - Ceramic
Fatigue failure cannot occur if the applied stress is below the material's yield stress. (True, False)
False
If a material is good in tension then it is good in compression. (True, False)
False
Increasing the mean stress does not affect fatigue life. (True, False)
False
Processing a material (welding, forming, grinding, etc...) does not change its physical properties. (True, False)
False
There is no maximum amount of cold work or deformation that can be performed on a metallic material before it becomes too brittle and break. (True, False)
False
_____________ steel consists of applying at thin coat of zinc to the steel. The zinc acts as a sacrificial _________.
Galvanized, anode
__________________ is another form of cathodic protection that applies a uniform low voltage throughout the hull of the ship.
Impressed Current
