MATE 210 Final
What are the Miller indices for the plane shown in the following cubic unit cell?
(102)
The close packed plane in a FCC unit cell is:
(111)
Grain boundaries are:
Region between crystals
What are the Miller indices for the plane shown in the following cubic unit cell?
(111)
The Miller Indices of Plane A with the origin moved to 0,1,0 is:
(2 2bar 0)
Tensile strength is determined by:
(c) The maximum stress before failure
For a lead-tin alloy of composition 25 wt% Sn—75 wt% Pb at 200°C, type the composition of Sn (in %wt) for �.
17
HCP metals are more brittle then FCC metals because:
FCC metals have more slip systems than HCP
The close packed plane in a BCC unit cell is
None
A lead-tin alloy of composition 30 wt% Sn-70 wt% Pb is slowly heated from a temperature of 150°C (300°F). At what temperature (in °C) does the first liquid phase form?
183
Figure below shows the tensile engineering stress-strain behavior for a steel alloy. (d) What is the maximum tensile strength?
1950 MPa
From the Pb Sn phase diagram below, at 100°C, what is the maximum solubility (in wt% Pb) of the following: Pb in Sn ( β )
2
If cupric oxide (CuO) is exposed to reducing atmospheres at elevated temperatures, some of the Cu2+ ions will become Cu+. How many Cu+ ions are required for the creation of each defect.
2
Calculate the number of vacancies per cm3 in iron at 950oC. The energy for vacancy formation is 1.08 eV/atom, and the density and atomic weight for Fe are 7.65 g/cm3 and 55.85 g/mol, respectively:
2.93E18 vacancies/cm3
What is the magnitude of the maximum stress that exists at the tip of an internal crack having a radius of curvature of 1.9 × 10-4 mm and a crack length of 3.8 × 10-2 mm when a tensile stress of 140 MPa is applied?
2800 MPa
What is the diffusion coefficient (D) for iron at 700oC, with an activation energy (Q) of 18,300 cal/mol, and Do=0.0047cm2/s:
3.64E-7 cm2/s
For a 60 wt% W alloy cooling down from 3400oC, the composition (in wt% W) of the last liquid to solidify is:
38
A FCC unit cell has how many atoms:
4
Calculate the maximum internal crack length allowable for a Ti-6Al-4V titanium alloy component that is loaded to a stress one-half its yield strength. Assume that the value of Y is 1.50. The yield strength is 910 MPa and the Mode I fracture toughness (KIC) is 55 MPa /�
4.1 mm
Cite the phase composition (in wt% Sn) of � for the following alloy: 15 wt% Sn at 100°C Type your answer for: Cα
5
From the Pb Sn phase diagram below, at 100°C, what is the maximum solubility (in wt% Sn) of the following: Sn in Pb ( α )
5
A brass strip previous cold rolled 33% is now 2.0-in thick. It is then cold rolled further to 1.50-in. how much cold-working has been done? (Note: in cold-rolling only thickness is decreasing):
50%
Calculate the % cold work in a copper cylindrical bar with an initial diameter of 17mm and a final diameter of 12mm
50%
Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure below), specify the nature of the final microstructure (in terms of microconstituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. Assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Rapidly cool to 600°C (1110°F), hold for 4 s, rapidly cool to 450°C (840°F), hold for 10 s, then quench to room temperature.
50% fine pearlite, 25% bainite, and 25% martensite
Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure below), specify the nature of the final microstructure (in terms of microconstituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. Assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Rapidly cool to 625°C (1160°F), hold for 10 s, then quench to room temperature.
50% medium pearlite and 50% martensite
A 65 wt% Ni-35 wt% Cu alloy is heated to a temperature within the α + liquid-phase region. If the composition of the α phase is 70 wt% Ni, determine: The composition (in wt% Ni) of the liquid phase
59
What is the composition, in weight percent, of an alloy that consists of 98g tin and 65g of lead :
60.1 wt% tin and 39.9 wt% lead
A lead-tin alloy of composition 30 wt% Sn-70 wt% Pb is slowly heated from a temperature of 150°C (300°F). What is the composition (in wt% Sn) of the first liquid phase to form?
61.9
An uncold-worked cylindrical steel rod with an initial diameter of 0.5in is drawn (cold-worked) down to a diameter of 0.3in. How much cold-working was done:
64%
12.29 Calculate the fraction of lattice sites that are Schottky defects for cesium chloride at its melting temperature (645°C). Assume an energy for defect formation of 1.86 eV.
7.87 x 10-6
For a 60 wt% W alloy cooling down from 3400oC, the composition (in wt% W) of the first solid phase to form is:
78
On the basis of ionic charge and ionic radii, predict crystal structures for the following compound at room temperature: -Compound: MgS - Cation Radius (nm): Mn2+ = 0.072 - Anion Radium (nm): S2- = 0.184
zinc blende structure, tetrahedral
For a 90 wt% Sn alloy at 200oC the amount of the phases would be:
~39.5% Liquid & 60.5% β-solid
From the lead-tin phase diagram, which of the following phases/phase combinations is present for an alloy of composition 46 wt% Sn-54 wt% Pb that is at equilibrium at 44°C?
α + β
Cite the phases that are present, the phase compositions, and the relative amounts (in terms of mass fractions) of the phases for the following alloy: 25 wt% Pb-75 wt% Mg at 425°C (800°F)
α phase: 25 wt% Pb-75 wt% Mg, Wα = 1.0
Phase transformations:
are time and temperature dependent
Nucleation
- nuclei (seeds) act as templates on which crystals grow - for nucleus to form rate of addition of atoms to nucleus must be faster than rate of loss - once nucleated, growth proceeds until equilibrium is attained
What are the Miller indices for the plane shown in the following cubic unit cell?
(011)
What are the Miller indices for the plane shown in the following cubic unit cell?
(1 0 0)
The Miller Indices of Plane B is
(1 2 2)
What are the Miller indices for the plane shown in the following cubic unit cell?
(101)
Yield strength is determined by:
(a) The stress at which dislocation start to move and increase in number (c) The point on the stress strain curve where the initial linear portion begins to curve over
A 65 wt% Ni-35 wt% Cu alloy is heated to a temperature within the α + liquid-phase region. If the composition of the α phase is 70 wt% Ni, determine: The mass decimal fractions (NOT %) of the � phase.
.55
For Fe - C steel with 0.50 wt% C steel at a temperature just below the eutectoid, determine the weight fraction of the Pearlite. HINT: the eutectoid point is at 0.76 wt% C and the maximum solubility of C in ferrite is 0.022 wt% C. Type your answer in DECIMAL form.
.648
List the point coordinates for all atoms that are associated with the BCC unit cell. Select multiple answers.
0 0 1 0 1 1 1 0 0 1 0 1 1 1 1 1/21/21/2 1 1 0 0 1 0 0 0 0
6.2FE A cylindrical specimen of brass that has a diameter of 20 mm, a tensile modulus of 110 GPa, is pulled in tension with force of 40,000 N. If the deformation is totally elastic, what is the strain experienced by the specimen?
0.00116
A 10mm diameter Titanium bar with an elastic modulus of 107GPa is subjected to a tensile load of 19,635N, what is the resulting strain:
0.00234
For Fe - C steel with 0.50 wt% C steel at a temperature just below the eutectoid, determine the weight fraction of Cementite. HINT: the eutectoid point is at 0.76 wt% C and the maximum solubility of C in ferrite is 0.022 wt% C. Type your answer in DECIMAL form.
0.072
Cite the relative amounts (in terms of mass fractions) of � for the following alloy: 15 wt% Sn at 100°C Type your answer in DECIMAL fraction for: Wβ
0.11
For a lead-tin alloy of composition 80 wt% Sn-20 wt% Pb and at 180°C (355°F) do the following: Determine the mass fraction (in decimals) of the total α phase.
0.224
For a lead-tin alloy of composition 80 wt% Sn-20 wt% Pb and at 180°C (355°F) do the following: Determine the mass fraction of β in the eutectic. Type your answer as a DECIMAL fraction.
0.27
Using the data for aluminum in Table 3.1, compute the interplanar spacing for the (110) set of planes.
0.2860 nm
What is the lattice parameter for an Iron BCC unit cell with an atomic radius of 0.1241 nm:
0.2866nm
For Fe - C steel with 0.50 wt% C steel at a temperature just below the eutectoid temperature, determine the weight fraction of the pro eutectoid ferrite. HINT: the eutectoid point is at 0.76 wt% C and the maximum solubility of C in ferrite is 0.022 wt% C. Type your answer in DECIMAL form.
0.352
A cylindrical specimen of a nickel alloy having an elastic modulus of 207 GPa and an original diameter of 10.2 mm experiences only elastic deformation when a tensile load of 8900 N is applied. Compute the maximum length of the specimen before deformation if the maximum allowable elongation is 0.25 mm.
0.475 m
For a lead-tin alloy of composition 80 wt% Sn-20 wt% Pb and at 180°C (355°F) do the following: Determine the mass fraction (in decimal) of eutectic microconstituents.
0.5
The atomic packing factor for aluminum with a FCC unit cell is:
0.74
Specify the order of operations to refine titanium ore into a metal using the Kroll process.
1. Heat TiO2 with chlorine and carbon in a sealed vessel to exchange the oxygen in chlorine, reacting to form TiCl4 2. Remove TiCl4 from impurities using a distillation process 3. Heat TiCl4 with Mg in a sealed vessel to release the Cl from Ti, reacting to form MgCl2 4. Remove MgCl2 from the Ti metal using electrolysis 5. Condense Ti metal sponge into a ignot using the vacuum arc process of heating
Estimate the theoretical fracture strength (in MPa) of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length 0.25 mm that has a tip radius of curvature of 0.004 mm when a stress of 1060 MPa is applied.
16,760 MPa
Figure below shows the tensile engineering stress-strain behavior for a steel alloy. (c) What is the yield strength at a strain offset of 0.002?
1600 MPa
10.4 (a) For the solidification of nickel, calculate the critical radius (in nm) r* and the activation free energy (in J) ΔG* if nucleation is homogeneous. Values for the latent heat of fusion and surface free energy are -2.53 × 109 J/m3 and 0.255 J/m2, respectively. Use the supercooling value found in Table 10.1. The melting temperature of Nickel is 1455 (C)
1.09 nm and 1.27 x 10-18J
If ice homogeneously nucleates at -40°C, calculate the critical radius (in nm) given values of -3.1 ×108 J/m3 and 25 × 10-3 J/m2, respectively, for the latent heat of fusion and the surface free energy.
1.1
For the solidification of palladium, calculate the critical radius (in nm) r* if nucleation is homogeneous. Values for the latent heat of fusion and surface free energy are -2.05 × 109 J/m3 and 0.235 J/m2, respectively. Palladium has a melting temperature of 1,555°C and is supercooled by 332°C below the melting temperature.
1.26
Calculate the number of vacancies per cubic meter at 1000°C for a metal that has an energy for vacancy formation of 1.22 eV/atom, a density of 6.25 g/cm3, and an atomic weight of 37.4 g/mol.
1.49 X 1024 m-3
Suppose that a steel of eutectoid composition is cooled to 675°C (1250°F) from 760°C (1400°F) in less than 0.5 s and held at this temperature. (a) How long will it take for the austenite-to-pearlite reaction to go to 50% completion? To 100% completion?
100 sec and 800 sec
Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure below), specify the nature of the final microstructure (in terms of microconstituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. Assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Cool rapidly to 350°C (660°F), hold for 103 s, then quench to room temperature.
100% Bainite
Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure below), specify the nature of the final microstructure (in terms of microconstituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. Assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Cool rapidly to 665°C (1230°F), hold for 103 s, then quench to room temperature.
100% coarse pearlite
Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure below), specify the nature of the final microstructure (in terms of microconstituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. Assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Rapidly cool to 300°C (570°F), hold for 20 s, then quench to room temperature in water. Reheat to 425°C (800°F) for 103 s and slowly cool to room temperature.
100% tempered martensite
A lead-tin alloy of composition 30 wt% Sn-70 wt% Pb is slowly heated from a temperature of 150°C (300°F). What is the composition (in wt% Sn) of the last solid remaining prior to complete melting?
13
A 65 wt% Ni-35 wt% Cu alloy is heated to a temperature within the α + liquid-phase region. If the composition of the α phase is 70 wt% Ni, determine: The temperature (in ∘C) of the alloy
1345
Figure below shows the tensile engineering stress-strain behavior for a steel alloy. (b) What is the proportional limit?
1370 MPa
Why is the TEM valuable in identifying hidden defects in layered structures?
A TEM can image through a complex stack in cross section, A TEM can provide excellent contrast when layers are of different composition, structures, or density. Chemical analysis is possible in the 1nm resolution.
The term Hypereutectic means:
A composition above the eutectic point
A Rockwell Hardness test measures:
A materials resistance to localized deformation
Pearlite, which is made up of ferrite and cementite, is:
A microconstituent within the microstructure of steel
When heat treating an alloy to increase its strength and toughness, it is desirable to have a microstructure of:
A soft ductile matrix encompassing numerous small, round, hard precipitates
A eutectic structure is:
A two phase microstructure with alternating layers of one another
Which of the following is not true about grain boundaries?
Equiaxed grains are found when cooling rate is lower.
About how fast is an electron moving in a TEM?
About 50% the speed of light
The annealing process is typically performed on a previously cold-worked metal to:
Allow recrystallization and the restoration of precold-worked properties
Briefly explain why, upon solidification, an alloy of eutectic composition (like steel) forms a microstructure consisting of alternating layers of the two solid phases.
Alternating layers will form at the eutectic temperature, even when the overall composition is NOT the eutectic composition. Any remaining metal that has not transformed into a a Pro-eutectic phase will solidify into the alternating layers at the eutectic temperature. During solidification of steel, austenite transforms to alternating layers of low carbon ferrite and high carbon iron carbide. This lamella structure is called Pearlite. Carbon diffuses along the solidification front in the austenite because diffusivity is lower here. During solidification, atomic diffusion must occur, and with this layering configuration the diffusion path length for the atoms is a minimum.
Explain why the properties of polycrystalline materials are most often isotropic.
Although each individual grain in a polycrystalline material may be anisotropic, if the grains have random orientations, then the solid aggregate of the many anisotropic grains will behave isotropically.
Plastically deforming a metal specimen near room temperature generally leads to which of the following property changes?
An increased tensile strength and a decreased ductility
Consider two edge dislocations of opposite sign and having slip planes that are separated by several atomic distances, as indicated in the following diagram. Briefly describe the defect that results when these two dislocations become aligned with each other, and later when they can move closer together. (select multiple answers)
Annihilation of the two edge dislocations when the vacancies can diffuse away, forming a perfect crystal Vacancies that extend into and out of the plane of the paper
Once a system is at a state of equilibrium, a shift from equilibrium may result by alteration of which of the following?
Any of them (temperature, pressure OR composition.
Interstitial sites are:
Are the voids in-between atoms in the crystalline structure.
10.3FE On the basis of accompanying isothermal transformation diagram for a 0.45 wt% C iron-carbon alloy, which heat treatment could be used to isothermally convert a microstructure that consists of proeutectoid ferrite and fine pearlite into one that is composed of proeutectoid ferrite and martensite?
Austenitize the specimen at approximately 775°C, rapidly cool to about 675°C, hold at this temperature for 1 to 2 s, and then rapidly quench to room temperature
In the following unit cell, which vector represents the [121] direction?
B
The crystalline structure of this unit cell is:
BCC - Body Center Cubic
The following metal specimen was tensile tested until failure. How would you characterize this metal?
Brittle
Which type of fracture is associated with intergranular crack propagation?
Brittle
Atoms of which of the following elements will diffuse most rapidly in iron?
C
What statements are true about CREEP?
Creep is deformation of a metal. Creep can be reduced when the grains are larger, columnar or single crystal. Creep occurs at high temperature and over long periods of time.
The 2017 Nobel prize in Chemistry was awarded in the area of?
Cryo-EM Biological TEM
Cite the phase compositions, and the relative amounts (in terms of mass fractions) of the phases for the following alloy: 85 wt% Ag-15 wt% Cu at 800°C (1470°F)
Cβ = 92 wt% Ag-8 wt% Cu, CL = 77 wt% Ag-23 wt% Cu, Wβ = 0.53, WL = 0.47
Hot-working is:
Deforming a metal at a temperature above its recrystallization temperature
Cold-working is:
Deforming a metal at a temperature below its recrystallization temperature
Cracks have a ____ effect on fracture toughness due to____:
Detrimental, their sharp points being stress concentrators
How is strain hardening used as a strengthening mechanism in metals? Multiple answers allowed.
Dislocation strain fields interact with other dislocation strain fields, resulting in their limited mobility. On average, the dislocations are repulsive to each other, so they eventually stop moving around. The dislocation density increases with greater cold working, so they become entangled and stop moving.
The types of dislocations are:
Edge, screw, mixed
Why are electrons so handy when you are making a microscope? Select more than one answer.
Electrons have a very short wavelength allowing for amazing resolution. Electrons have strong scattering by matter giving excellent contrast. Electrons can be easily focused with magnetic lenses
A "cup and cone" fracture surface on a tensile specimen indicates the metal was most likely brittle.
False
A Frenkel defect is a paired set of cation and anion vacancies.
False
A P-type semiconductor has one EXTRA electron than the pure intrinsic semiconductor.
False
A Schottky defect is a cation vacancy-cation interstitial pair.
False
Steel is more susceptible to fatigue failure than aluminum.
False
For a 0.95% C steel at room temperature, the PHASES present are:
Ferrite & Cementite
Suppose that CaO is added as an impurity to CaCl2. If the O2- substitutes for Cl-, what kind of vacancies would you expect to form? How many of these vacancies are created for every O2- added?
For O2- substituting for Cl- in CaCl2, chlorine vacancies would be created. For each O2- substituting for a Cl-, one negative charge is added; negative charges are eliminated by creating chlorine vacancies. In order to maintain charge neutrality, one O2- ion will lead to the formation of one chlorine vacancy.
Compare interstitial solid solutions and substitutional solid solutions. Multiple answers allowed.
For substitutional solid solutions, both elements must have the same crystal structure. For substitutional solid solutions,atomic diameters and electronegativities for both atom types must be similar. For substitutional solid solutions, impurity atoms substitute for host atoms. For substitutional solid solutions, the impurity atoms must have a valence that is the same as or less than the host material. Interstitial solid solutions form for relatively small impurity atoms that occupy interstitial sites among the host atoms.
Martensitic transformation:
Happens at temperatures below the eutectiod temp and is diffusionless
How is solid solution strengthening used as a strengthening mechanism? MULTIPLE ANSWERS MAY EXIST.
High-purity metals are almost always softer and weaker than alloys composed of the same base metal. An edge dislocation is attracted to substitutional defects because the strain energies are opposite so they can cancel out some of this strain. Impurity atoms are added that go into solid solution imposing a lattice strains on the surrounding host atoms. Lattice strain field interactions between dislocations and these impurity atoms restrict dislocation motion.
Interstitial atoms are:
Impurity atoms that fill the void between host atoms
Which one of the following is NOT a type of point defect?
Inclusion
Cold-working strengthens a metal by:
Increasing the number of dislocations which then interfere with other dislocations
In most metal alloys the most rapid mode of diffusion is:
Interstitial diffusion
What is the burgers vector?
It defines the magnitude AND type of lattice distortion in a dislocation.
Why is titanium such a rare and expensive metal to produce?
It is sensitive to chlorine contamination and requires pure water to cool it. Forging with a press requires intensive pressure. using specially designed presses. It has a low thermal conductivity making it difficult to machine from a solid. It is difficult to refine the ore into a pure metal.
What statement is true regarding a semiconductor?
It will have MUCH better conductivity if impurities with more or less electrons in their outer shell are added.
Dislocations are:
Linear defects
Select all of the major steps in a WAFER FABRICATION process.
Litho Etch Diffusion and Implant Thin Film deposition Chemical Mechanical Planarization (CMP)
Dislocations in metals allow:
Material deformation
In the figure below, indicate the location in the vicinity of an edge dislocation at which an interstitial impurity atom would be expected to be situated. In terms of lattice strains why it would be situated at this position.
One extra interstitial atom is placed just below the edge dislocation. This relieves some of the tensile strain that would normally exist below the extra half plane.
A Phase Diagram:
Only displays the phases present at equilibrium
For a 0.77% C steel at room temperature, the MICROCONSTITUENT(S) present are:
Pearlite
Substitutional defects are:
Point defects
Suppose that CaO is added as an impurity to Li2O. If the Ca2+ substitutes for Li+, what kind of vacancies would you expect to form? How many of these vacancies are created for every Ca2+ added?
Positive charges are eliminated by creating lithium vacancies, and for every Ca2+ ion added, a single lithium vacancy is formed.
What are the most likely defects possible for Al2O3 as an impurity in MgO? Hint: Cation and anion valence states are: Mg2+ Al3+ O2-
Positive charges are removed by creating Mg2+ vacancies.
The Transmission Electron MIcroscope (TEM) is an essential tool for: (select more than one)
Production Research and Development (R & D) Failure Analysis Customer Returns Competitor Evaluation
What are the conditions favorable for substitutional solid solutions (S.S.) i.e. the W. Hume - Rothery rule. MULTIPLE ANSWERS MAY EXIST.
Same crystal structure for pure metals All else being equal, a metal will have a greater tendency to dissolve a metal of higher valency than one of lower valency Δr (atomic radius) < 15% Close proximity in periodic table;•i.e., similar electronegativities
Why is crystallographic slip easiest on close packed planes and in close packed directions. MULTIPLE ANSWERS MAY EXIST.
Slip is in the direction of the closed-packed direction because the atoms can stay closer together and less deviation from the low energy equilibrium bond distance. There are less number of bonds connecting close-packed planes so less bonds need to break when the two close-packed planes slide past each other. Surface energy is lowest on the close packed planes because the in-plane bond density is the highest, and the out-of-plane bond density is lowest.
Why are small-angle grain boundaries not as effective in interfering with the slip process as are high-angle grain boundaries. Select only one answer.
Small angle grain boundaries do not have as much crystallographic misalignment in the grain boundary region for small-angle, and therefore not as much change in slip direction.
How can grain size reduction be used as a strengthening mechanism? (assume grains are near room temperature)
Smaller grains means more grain boundaries. Grain boundaries are obstacles to dislocation motion because they must change direction when transitioning from one grain to another.
On the basis of ionic charge and ionic radii given in the table below, predict crystal structures for the following material: CaO
Sodium Chloride
On the basis of ionic charge and ionic radii given in the table below, predict crystal structures for the following material: KBr
Sodium chloride
The figure below shows the tensile engineering stress-strain behavior for a steel alloy. (a) What is the modulus of elasticity?
Somewhere between 200 GPa and 210 GPa
Fick's first law of diffusion is used for:
Steady state diffusion
What are true statements relating to the phenomena of superheating and supercooling and why it occurs? There are multiple correct answers.
Supercooling and superheating is larger for homogeneous nucleation because nuclei form in the bulk of the liquid and a stable nucleating surface is not available. Superheating and supercooling correspond, respectively, to heating or cooling above or below a phase transition temperature without the occurrence of the transformation. Superheating and supercooling occur because right at the phase transition temperature, the driving force is not sufficient to cause the transformation to occur. The driving force is enhanced during superheating or supercooling. The critical radius of a nuclei is smaller when the supercooling is larger.
Will Mg-Zn exhibit complete solid solubility? Information is provided in the table below. Mg - atomic radius (nm): 0.160 - Crystal structure: HCP - Electronegativity: 1.3 - Valence: +2 Zn - atomic radius (nm): 0.133 - Crystal structure: HCP - Electronegativity: 1.7 - Valence: +2
They will never have complete solubility because their atomic radii difference is not less than 15%
When two identical edge dislocations move close to one another, how will this affect the mechanical properties of the metal. Select more than one answer.
The dislocations will pile up and entangle in each other, resulting in a loss of ductility (workability) and an increase in tensile strength. The edge dislocations will repel each other. This will result in an a reduction in ductility and increase in tensile strength.
Solvent in terms of solid solution alloys is:
The element that is present in the greatest amounts
The hardness and brittleness in Martensite is caused by:
The interstitial Carbon atoms trapped in the BCT microstructure blocking dislocation movement
A slip system describes the slip plane and the slip direction.
True
Diffusion is:
The movement of atoms in a material, typically from high concentrations to lower concentrations
Recrystallization is:
The nucleation and growth of new grains that are strain-free
Creep is:
The plastic deformation of a material at elevated temperatures due to a load lower than its yield strength
What are some research efforts to extend Moore's Law, the doubling of the number of transistors on a chip every 18 months. Select more than one answer.
The shift from Fin-FET's to Gate-All-Around transistors Directed Self-Assembly with block co-polymer photoresists. Quantum Devices (Also called Single Electron Transistors (SET's) Photolithography with even shorter wavelength than Extreme UV Compound semiconductors with higher mobility like GaAs
As the amount of cold-working to a metal is increased the typical effect on some of its properties are:
The tensile strength increases; the ductility decreases; the yield strength increases
Dislocation motion is difficult in ceramics because bonding is directional and like charged atoms repel each other.
True
Which of the following is/are true about grain boundaries?
This area has a low density This area is more chemically reactive It is the transition from the lattice of one region to that of the other It is the region between crystals
According to the video documentary, why was the SR-71 made with titanium?
Titanium has a higher strength to weight ratio than other metals. The high speed of the SR-71 created high temperatures that titanium could withstand.
Charpy Impact test are used to help determine a metals:
Transition Temp and Toughness
Dislocations entangle with one another during cold work, making them more difficult to move.
True
Heterogeneous nucleation occurs at a much smaller supercooling because nucleation occurs on surfaces instead of the bulk material. The surface to volume ratio of the nuclei is smaller, which translates into a smaller surface free energy to volume free energy ratio. Surface free energy destabilizes the nucleus.
True
In crystalline solids, if dislocations can't move, plastic deformation doesn't occur.
True
In crystalline solids, if dislocations can't move, plastic deformation doesn't occur. HINT, THIS IS A TRUE FACT.... True or False: Dislocation motion occurs during creep.
True
Silicon doped with arsenic is an N-Type semiconductor. HINT: On the periodic table, arsenic is a group V element, and positioned to the RIGHT of silicon.
True
Silicon doped with boron is a P-Type semiconductor. HINT: On the periodic table, boron is a group III element, and positioned to the LEFT of silicon.
True
Slip is easiest along close packed planes because they have the lowest number of bonds connecting adjacent close-packed planes. Less bonds need to break when the two close packed planes slide past each other.
True
Slip is easiest along closed-packed directions because the atoms can stay closer together. There is less deviation from the low energy equilibrium bond distance.
True
The recrystallized grains from heat treated metal that was previously cold worked produces much smaller grains initially.
True
The two factors that determine the structure of ceramics are: 1) relative size of the cation / anions and 2) maintenance of charge neutrality.
True
Two forms of carbon are diamond and graphite.
True
Vacancy defects are:
When a host atom is missing from a normally occupied site in a crystalline structure
Compare the two stress/strain diagrams below, then select the correct answer from the questions.
Which sample has greater ductility? 6 Which sample has greater fracture strength? 6 Which sample has greater yield strength at a strain offset of 0.002? 1 Which sample has a greater ultimate tensile strength? 1
If you were building a guard-rail on a bridge in an area that can reach temperatures as low as-20oF, you would want to use a steel:
With a DBTT below -20'F
On the basis of ionic charge and ionic radii given in the table below, predict crystal structures for the following materials: MnS
Zinc blende
Identify the direction of the vector shown in the unit cube below.
[0 1 1]
Identify the direction of the vector shown in the unit cube below.
[2bar 1 0]
On the basis of ionic charge and ionic radii, predict crystal structures for the following compound at room temperature: -Compound: CsBr - Cation Radius (nm): Cs+ = 0.170 - Anion Radium (nm): Br- = 0.196
cesium chloride structure, cubic
If cupric oxide (CuO) is exposed to reducing atmospheres at elevated temperatures, some of the Cu2+ ions will become Cu+. Under these conditions, name the possible crystalline defect(s) that you would expect to form in order to maintain charge neutrality. (multiple answers are allowed)
creating O2- vacancies creating Cu2+ interstitials
What defect was causing shorts in the silicon transistors.
dislocations
A dislocation formed by adding an extra half-plane of atoms to a crystal is referred to as a (an)
edge dislocation
7.4 For each of edge, screw, and mixed dislocations, cite the relationship between the direction of the applied shear stress and the direction of dislocation line motion.
edge dislocation—applied shear stress and dislocation line motion are parallel to each other screw dislocation—applied shear stress and dislocation line motion are perpendicular to each other mixed dislocation--neither parallel nor perpendicular
What is the primary strengthening mechanism in aircraft aluminum?
precipitation hardening
For a 0.50% C steel at room temperature, the MICROCONSTITUENT(S) present are:
pro-eutectoid Ferrite & Pearlite
On the basis of ionic charge and ionic radii, predict crystal structures for the following compound at room temperature: -Compound: KI - Cation Radius (nm): K+ = 0.138 - Anion Radium (nm): I- = 0.220
sodium chloride structure, octahedral
What is the primary strengthening mechanism in gold jewelry?
solid solution alloying
Pearlite transforming from Austenite, forms a layered structure:
to minimize the amount of diffusion that is needed
