MSE Exam 2

At constant pressure, in binary equilibrium phase diagram, when there are 3 phases in equilibrium, the degree of freedom will be:

0

In a eutectic reaction at eutectic temperature, were three phases are at equilibrium, the degree of Freedom is:

0

A cylindrical specimen of a metal alloy 10 mm (0.4 in.) in diameter is stressed elastically in tension. A force of 15,000 N (3,370 lbf) produces a reduction in specimen diameter of 7 × 10^-3 mm (2.8 × 10^-4 in.). Compute Poisson's ratio for this material if its elastic modulus is 100 GPa (14.5 × 106 psi).

0.367

Heat treating cold worked metals brings about changes in structure and properties. Select the one which is not right.

1 hour treatment at T anneal increases tensile strength & decreases %EL

Stages of Moderately Ductile Failure Put the stages into the correct order in which they occur.

1) necking 2) void nucleation 3) void growth and coalescence 4) crack propagation 5) fracture

In the Cu-Ni Phase diagram shown in the above questions, the number of the component is

1, 2, 1 respectively

A specimen of copper having a rectangular cross section 15.2 mm × 19.1 mm (0.60 in. × 0.75 in.) is pulled in tension with 44,500 N (10,000 lbf) force, producing only elastic deformation. Calculate the resulting strain. The elastic modulus for Cu is given in Table 7.1 as 110 GPa (or 110* 10^9 N/m2).

1.39 * 10-3

The time for the fraction of residual cold work in iron to drop to 0.6 at 400°C is 137 minutes, and at 450°C it is 15 minutes. Calculate the activation enthalpy for the recovery of cold work in iron. Take k=8.62*10^-5 eV/atom.K

1.85 eV/atom

What is the maximum amount of Pb that can be in the beta phase? Answer in wt%.

100=97.8=2.2

What is the lowest temperature of the liquidus? Answer in C

1148 (point A of L)

Suppose that a wing component on an aircraft is fabricated from an aluminum alloy that has a plane-strain fracture toughness of 26.0 MPa m^0.5 (23.7 ksi in^0.5). It has been determined that fracture results at a stress of 112 MPa (16,240 psi) when the maximum internal crack length is 8.6 mm (0.34 in.). For this same component and alloy, compute the stress level at which fracture will occur for a critical internal crack length of 6.0 mm (0.24 in.).

134 Mpa

Based on the Fe-C phase diagram shown, the peritectic temperature is;

1493 C

An aircraft component is made from a material that has KIc = 26 MPa-m^0.5 It has been determined that fracture results at a stress of 112 MPa when the maximum (critical) surface crack length is 9.0 mm. For this same component and alloy, compute the stress level at which fracture will occur for a critical surface crack length of 4.0 mm.

168 MPa

In the Pb-Sn Phase Diagram shown, The maximum solubility for Sn in Pb is;

19 wt% Sn

In the Cu-Ni Phase diagram shown in the above questions, the number of the component is

2

Phase Diagrams are constructed and used at the constant pressure of 1 atm. Which point has one (1) degree of freedom?

2 wt% C, 1300˚C (y+L)

Based on the Fe-C phase diagram shown, the maximum solubility of carbon in Gama iron (Austenite) i

2.14 wt% C

In the Al Ni equilibrium phase diagram, for the alloys with 17-37 atomic %Ni, the number of phase(s) is(are) present at 854 C?

3

For Cu-35 wt% Ni solidification, the composition of the last liquid is

32 wt%Ni HOW TO SOLVE: look at the 35% and go up until you reach the solid section. Then move horizontally until the liquid section is touched (around 32)

The yield point for an iron that has an average grain diameter of 1 × 10-2 mm is 230 MPa (33,000 psi). At a grain diameter of 6 × 10-3 mm, the yield point increases to 275 MPa (40,000 psi). At what grain diameter will the lower yield point be 310 MPa (45,000 psi)?

4.34*10^-3

For Cu-35 wt% Ni solidification, the composition of the first solid is;

43 wt%Ni HOW TO SOLVE: look at 35% and go up until reached the liquid section. Then move horizontally until the solid section is touched (around 43)

A force of 1200 N is applied axially to a latex rubber sheet that is initially 0.250 m long, 0.020 m wide, and 0.00100 m thick. The new dimension of the sheet when subject to the load are 1.750 m long, 0.009 m wide, and 0.00046m thick. Calculate the engineering strain and true strain.

6.00 and 1.95

In the Pb-Sn phase Diagram shown, which alloy has the lowest melting temperature?

62 wt% Sn

An aluminum bar 125 mm (5.0 in.) long and having a square cross section 16.5 mm (0.65 in.) on an edge is pulled in tension with a load of 66,700 N (15,000 lbf) and experiences an elongation of 0.43 mm (1.7 × 10-2 in.). Assuming that the deformation is entirely elastic, calculate the modulus of elasticity of the aluminum.

712 GPa

Match the diagram to the type of dislocation motion it shows. Diagram A Diagram B

A = edge dislocation B= screw dislocation

Match each letter with its corresponding mechanical property term. (image is a tensile strain vs strain graph, a green line with a blue/red colored area)

A region= Elastic Deformation (linear strain distance) B region= Plastic Deformation (curved strain distance) C line = Elastic Modulus (Young's) D area = resilience E point = yield strength F point = tensile strength G point = failure H line = ductility D+H area = toughness

Elastic Modulus matching: y-axis=E (GPA) columns left to right=A, B, C, D

A=metals, alloys B=graphite, ceramics, semiconductors C=polymers D=composites/fibers

Which of the following is not expected to happen in the solid-solution strengthening mechanism?

An interstitial atom in the compressive strain region of an edge dislocation.

Consider the following alloy and temperature. C0= 35 wt% Ni At TB = 1250°C What phase(s) is/are present?

Both ⍺ and L present The alloy point is in two phase field, so we use tie line. CL= C liquidus ( = 32 wt% Ni ) Cα = C solidus ( = 43 wt% Ni )

Which one is RIGHT?(Select only one)

Ceramics—Ionically Bonded - Examples: NaCl, MgO - Dislocation motion—relatively difficult - Few slip systems motion of nearby ions of like charge (+ and -) restricted by electrostatic repulsive forces Ceramics—Covalently Bonded - Examples: silicon, diamond - Dislocation motion—relatively difficult - Covalent bonding—directional In Metals such as Copper, Aluminum, Iron, Dislocation motion—relatively easy - Metallic bonding—non-directional - Close-packed planes and directions for slip

Dislocation Characteristics of Ceramics Choose all the characteristics that apply to the material shown in the diagram. BLACK DOTS

Covalent bonding—directional Examples: silicon, diamond Dislocation motion—relatively difficult

Stress vs. strain curve of three different polymers are shown on the graph. Match each polymer to the appropriate curve (A-C).

Curve A steep = brittle polymer Curve B middle = plastic Curve C low = elastomer

Choose correct answers

Decreasing T increases TS Decreasing T has the same effects as increasing strain rate

For FCC crystal structure - slip system is {111}<110>. Select the statement that is NOT true..

Dislocation motion on {110} planes

Dislocation Characteristics of Ceramics Choose all the characteristics that apply to the material shown in the diagram BLACK AND WHITE DOTS

Dislocation motion—relatively difficult motion of nearby ions of like charge restricted by electrostatic repulsive forces Examples: NaCl, MgO Ionically Bonded

Which statement is NOT TRUE?

Ductility = the area under the engineering stress strain curve.

Which statement is not right?

Edge dislocations whose tangent and Burger's vector are not on a most closely packed plane are mobile.

Match the appropriate mechanical property to its d

Elastic Modulus (E): the linear strain vs stress relationship Yield Strength: stress at which plastic deformation occurs Ductility: amount of plastic deformation as failure Resilience: total area under the elastic curve Toughness: total area under the plastic curve Tensile Strength: maximum stress

Identify locations (if any) of composition and temperature where the following reactions take place.

Eutecoid: B Eutectic: A Peritectic: G Liquidus: D Single Phase Region: E

Identify locations (if any) of composition and temperature where the following reactions take place.

Eutecoid: alpha + Fe3C (A) Eutectic: L (B) Peritectic: 𝓈 (D)

For Brittle fracture, select one that does not apply;

Extensive plastic deformation

Which materials are ductile at lower temperatures?

FCC metals HCP metals

Select one that best describes Ductile fracture;

Fails with warning Accompanied by significant plastic deformation Slow crack propagation

Decreasing temperature (T) decreases tensile strength (TS). (TRUE or FALSE)

False

Which one in not true?

Fracture strain of Ceramics is about 10%.

Which of the following is a eutectoid reaction?

Gama phase to Alpha phase plus Beta phase

Which one is not a correct statement?

If a crystal contains only two positive edge dislocations with Burger's vectors of opposite signs, and they come together on the same slip plane the resulting number of dislocations is equal to one.

Which one is not right?

In a peritectic reaction, two liquids combine to form a solid.

Select the right statement

In a phase diagram, the liquidus line gives the temperature where the first solid forms upon cooling an alloy of given composition C from the liquid phase.

Strain hardening or Cold work:

Increases the yield strength

Which statement is NOT right?

Increasing temperature decreases the impact energy

In polymers, increasing strain rate causes

Increasing the tensile strength

Which one of the following is not true about the role of fracture toughness in measuring the resistance of a material to brittle fracture?

Kc is measured in a tensile test.

Using the Ai-Ni phase diagram shown, for an alloy with original chemical composition of 25 atom percent Ni and 75 percent Al, determine the phases present at the following temperatures: 855°C, 854°C, and 853°C.

L + Al3Ni2, L + Al3Ni2 +Al3Ni, and Al3Ni

In considering the high-temperature creep of a turbine blade, which types of analysis would be the most important?

Larson-Miller parameter

What phases do you have present at 30 atom% Ni and 1000oC?

Liquid and Al3Ni2

Fracture Toughness is:

Measure of material's resistance to brittle fracture when a crack is present

Using the Pb-Sn phase diagram, for the alloy with 40 atom% Sn, which sentence is NOT right?

Melting starts at about 265 °C

Which statement is NOT TRUE?

Modulus of resilience is the area under engineering stress-strain curve up to fracture.

The unit of Stress is

Newton per square meter

For an alloy of two different elements A and B, at one atmosphere of pressure three phases are in equilibrium (α, β, and liquid), and it is desired to keep all three phases in equilibrium. Which of the following statements is true?

Nothing can be changed.

Consider the following alloy and temperature. C0= 35 wt% Ni At TA = 1320°C: What phase(s) is/are present?

Only Liquid (L) present CL = C0 ( = 35 wt% Ni)

Which of the following is not true?

Permanent strain is anelastic strain.

These pictures show different stages of annealing. Put them in the correct order.

Picture A Third Picture B Sixth Picture C Second Picture D First Picture E Fifth Picture F Forth trend: gains texture and becomes more fragmented, then becomes solid colors and becomes more cohesive)

Which of the following materials would you expect to have the lowest Young's modulus?

Polyethylene,(PE)

Stages of Annealing Stages of annealing - graph Match the labels to the graph, using the terms below. Two answers have been given as an example. Recrystallization Ductility Ductility (%EL) annealing temperature (°C) tensile strength Recovery Grain Growth tensile strength (MPa) Examples Grain Growth = 3 Tensile strength (MPa) = 6

Recrystallization (middle orange) 2 Recovery (first blue) 1 Ductility (%EL) (right y-axis) 8 Tensile Strength (top line) 4 Annealing Temp (x-axis) 7 Ductility (bottom line) 5

If S is the engineering stress and ST is true stress, and e is engineering strain, choose the proper conversion equation(valid until necking),

ST=S(1+e)

Where is steady-state creep?

Secondary Creep

Which of the following is not necessary for a continuous-solid solution?

Similar atomic numbers.

Which one is NOT right?

Slip System—Combination of Dislocation line and Burgers vector

Which one is not a true statement;

Smallest, most highly stressed cracks grow first!

Which statement is NOT TRUE?

Tensile Strength(TS)= the stress at the onset of noticeable plastic deformation.

For continuous solid solubility in 2 component systems (isomorphous systems) which of the following is not correct;

The atomic number must be the same

Strain-hardening in metals is due to

The creation of immobile dislocations by dislocation reactions

Which of the following best describes the microstructure resulting from a eutecticreaction?

The grains contain alternating plates or rods of the α and β phases.

Usually in cycling loading; select the correct answer

The higher the stress the lower the number of cycles to failure

The toughness of a material is:

The strain energy per unit volume needed to fracture the material.

Which statement is NOT true:

The tensile strength of ceramics can be 10 times greater than the compression strength.

In Eutectic Phase Diagram between two components A and B,

There is limited solubility of B in A and limited solubility of A in B.

Decreasing temperature (T) decreases ductility (%EL). (TRUE or FALSE)

True

Decreasing temperature (T) increases the elastic modulus (E). (TRUE or FALSE)

True

Match the curves to their type of materials

Upper green curve FCC and HCP metals Middle pink curve BCC metals and polymers Lower blue curve Ceramics and high strength materials

As %CW decreases

Yield strength (σy) decreases.

Which statement is NOT TRUE?

Yield strength = strain at which noticeable plastic deformation has occurred

The ratio of the applied normal stress to the elastic strain is

Young Modulus.

If elements A and B chemically bond to each other more strongly than a random mixture of A and B elements chemically bond, it is expected that

a compound of A and B should form.

Reducing grain size causes; (Select one that does not apply)

decrease yield strength, tensile strength & hardness

The unit of Strain is

dimensionless

The unit of True Strain is

dimensionless

If eT is true strain, and e is the engineering strain, select the proper Conversion Equations, (valid only to the onset of necking)

eT = ln(1+e)

Highest yield strength

highest tensile stress point (highest up y-axis)

Highest toughness

largest area under curve

The ratio of the tensile fracture strength of ceramics to the compressive fracture strength is typically:

less than 1

Highest elastic modulus

line w/ greatest slope

In a binary phase diagram, the ................ line gives the temperature above which there is no solid phase.

liquidus

Highest ductility

longest tensile strain (longest down x-axis)

Which one is TRUE?

magnitude of applied tensile stress is amplified at the tips of these cracks

For any Alloy of Pb with Sn content in the range of 29-98.6 atomic% Sn,

melting start at 183 degrees C

Brittle Fracture Choose the appropriate descriptions of the characteristics.

rapid crack propagation fails without warning little to no plastic deformation generally the less desirable ductile fracture

"If we know T and C0, then we can determine..."

the composition of each phase. the weight fraction of each phase. which phase(s) is (are) present.