# Shared Flashcard Set

## Details

Material Science Midterm 2
Ch. 4 & 5
101
Engineering
11/08/2015

Term
 Heat (Q) is the amount of _____ that is transferred from an area at high temperature to low temperature
Definition
 energy
Term
 When the temperature of a material is increased, the ____ of the lattice vibrations increase
Definition
 vibrations
Term
 For a mole of material, the increment of heat (dQ) added to the material divided by the change in temperature (dT) is the ____.
Definition
 heat capacity
Term
 The heat capacity is also known as the ______.
Definition
 molar specific heat
Term
 Specific heat (c) is the heat per unit _____.
Definition
 mass
Term
 The primary reason for the high specific heat of polymers is their ______.
Definition
 low monomer mass
Term
 In semi-crystalline polymers, there is a spike in the specific heat when the crystallites start to ____.
Definition
 melt
Term
 The sum of kinetic and potential energy is equal to the ____.
Definition
 internal energy
Term
 For a material that has no applied fields, the major contribution to the potential energy is the energy of _____.
Definition
 chemical bonding
Term
 The ____ is the internal energy plus the pressure times the volume. (E + PV)
Definition
 enthalpy
Term
 Internal energy is a _____.
Definition
 state variable
Term
 In a solid, the average kinetic energy is equal to the ______.
Definition
 average potential energy
Term
 The high-temperature heat capacity at constant volume for a solid or liquid is equal to ___.
Definition
 3R
Term
 The change in length of a material per degree divided by the original length is the _____.
Definition
 linear coefficient of thermal expansion
Term
 A(n) ____ material has the same properties in all directions.
Definition
 isotropic
Term
 For a polymer filament, the linear coefficient of thermal expansion would be ____ in the axial direction than in the transverse direction.
Definition
 less
Term
 A material with an interatomic potential perfectly symmetric about the equilibrium interatomic separation would have a coefficient of thermal expansion equal to ____.
Definition
 zero
Term
 Copper melts at 1085 C and platinum melts at 1769 C. Which material should have the smaller coefficient of thermal expansion?
Definition
 platinum
Term
 In heat transfer, the heat flux is directly related to the ____.
Definition
Term
 Diamond has a notably high thermal conductivity because of its ____.
Definition
 strong chemical bonding
Term
 What has the higher thermal conductivity, metallic aluminum or aluminum oxide?
Definition
 Metallic aluminum
Term
 Which should have the higher thermal conductivity, a sign-crystal gas-turbine blade or a polycrystal turbine blade?
Definition
 single-crystal
Term
 HDPE is more crystalline than LDPE, and ____ should have a lower thermal conductivity.
Definition
 LDPE
Term
 The diffusion of atoms of similar size depends upon the presences of ____.
Definition
 vacancies
Term
 The entropy of a perfect crystal at absolute zero kelvin with the atoms at rest is equal to ____.
Definition
 zero
Term
 A mole of pure argon gas has ___ less entropy than a mixture of a half mole of argon and a half mole of neon.
Definition
 less
Term
 What has the greater entropy, ice or water?
Definition
 water
Term
 When the equilibrium concentration of vacancies is present in a crystal at constant temperature and pressure, the Gibbs free energy is at a(n) _____.
Definition
 minimum
Term
 The probability that the energy to create a vacancy in a crystal is present in excess of the average energy in the crystal is given by the _____.
Definition
 Maxwell-Boltzmann probability distribution
Term
 If at constant temperature and pressure a change in a system produces a negative change in Gibbs free energy, the change is _____.
Definition
 spontaneous
Term
 The rate of change in a system depends upon the _____.
Definition
 activation enthalpy.
Term
 If the natural log of the rate of a thermally activated process is plotted on the y-axis as a function of the inverse of the absolute temperature on the x-axis, the slope of the plot is the ______ divided by _____.
Definition
 activation enthalpy, Boltzmann's constant
Term
 The activation enthalpy for vacancy diffusion contains two contributions: the activation enthalpy for ______ and ______.
Definition
 vacancy formation, atom migration
Term
 Which would have the higher activation energy for diffusion, carbon in iron or nickel in iron?Atomis radius of carbon = .077nmAtomic radius of nickel = .124nmatomic radius of iron = .124nm
Definition
 Nickel in iron
Term
 The activation enthalpy for self-diffusion is directly related to the ____.
Definition
 strength of chemical bonding
Term
 The activation enthalpy for vacancy diffusion along a grain boundary is ___ than that for diffusion through a bulk.
Definition
 less
Term
 In the most general form of the first law of diffusion, the gradient of the Gibbs free energy with respect to the position of the B-type atoms is equal to the ____ on the B-type atoms.
Definition
 chemical force
Term
 Amorphous polymers are ____ subject to mixing with solvents than are crystalline polymers.
Definition
 more
Term
 The solubility parameter of polycarbonate is 20.3 (MPa)^.5 and for carbon disulfide is 20.4 (MPa)^.5. Should carbon disulfide dissolve polycarbonate?
Definition
 Yes
Term
 The solubility parameter of polyethylene is 16.6 (MPa)^.5 and for ethanol is 26.0 (MPa)^.5. Should ethanol dissolve polyethylene?
Definition
 No
Term
 The solubility parameter of a polymer is related to the _____ for the polymer.
Definition
 energy of vaporization
Term
 The enthalpy of mixing for a pair of polymer molecules is related to the ____ of the two molecules.
Definition
 interaction parameter
Term
 The science of changing the activation enthalpy of a process is called ___.
Definition
 catalysis
Term
 The internal energy of a material depends on what? Does not depend on what?
Definition
 Energy of defects in the materialKinetic energy of the vibrating atomsBond energy between atomsNet energy resulting from a history of heating and cooling
Term
 Correctly order from high to low thermal conductivityHDPE, PMMA, LDPE, OUHMWPE
Definition
 OUHMWPEHDPELDPEPMMA
Term
 What results in high thermal conductivity? What does not?
Definition
 Strong bondingFree electronsSmall interatomic distancesGrain boundairs
Term
 Which of the following material states has the highest entropy?Amorphous solid, vapor, liquid, single crystal
Definition
 vapor
Term
 Which is not a thermodynamic state variable?GFE, Entropy, Heat, Enthalpy
Definition
 Heat
Term
 The mixing of which pair of atoms does not occur by vacancy diffusion?Gold and silverCopper and nickelPlatinum and palladiumHydrogen and palladium
Definition
Term
 Which of the following polymer combinations is least likely to mix?Liquids of two different LCMs with a negative enthalpy of mixing.A liquid solvent and solid polymer with solubility parameters of 19 MPa^.5 and 20 MPa^.5, respectivelyLiquids of two different LCMs with a positive enthalpy of mixingLiquid of two different short molecules with a positive enthalpy of mixing
Definition
 Liquids of two different LCMs with a positive enthalpy of mixing
Term
 If a transformation from a solid --> liquid occurs such that the solid and liquid are always in equilibrium, than the transformation is ____.
Definition
 reversible
Term
 A transformation occurs in a material, and the GFE change in the material is negative, then the transformation is ____.
Definition
 spontaneous
Term
 When α-phase iron is in equilibrium with iron carbide, the iron atoms in the two phases have equal ____.
Definition
 chemical potential
Term
 Nickel and silver have lattice parameters of 0.352 nm and 0.408 nm, respectively; an electronegativity of 1.8 for each, an FCC structure, and a similar valence. Should they be able to form a continuous-solid solution?
Definition
 No (Hume-Rothery rule)
Term
 In a phase digram, the ____ gives the temperature where the first solid forms upon cooling an alloy of given composition C0 from the liquid phase.
Definition
 liquidus line
Term
 In a phase diagram, the ____ gives the temperature where the first liquid forms upon heating an alloy of given composition C0 from the solid phase.
Definition
 solidus line
Term
 When a liquid copper-nickel alloy is rapidly cooled, the center of the grains has a higher concentration of nickel atoms than the average concentration. This is ____.
Definition
 coring
Term
 The purity of an alloy is given by the ___.
Definition
 chemical composition
Term
 The ___ gives the weight of material present in each phase of a two-phase region, but this says nothing about the phase purity.
Definition
 weight fraction
Term
 For a binary phase diagram in a two-phase region, use the ____ to find the atom or weight fraction of the phases present.
Definition
 lever rule
Term
 The ____ in a phase diagram separates the α-phase field from the α+β-phase field, and it gives the maximum solubility of the B-type atoms in the A-type crystal.
Definition
 α solvus line
Term
 Solders are made from metals with a(n) _____, because alloys of the metals melt at a temperature lower than that of either of the two components individually.
Definition
 eutectic phase diagram
Term
 When two elements form a eutectic phase diagram, in the eutectic reaction the atoms of the solid elements ____ or ____.
Definition
 segregate, separate
Term
 At a pressure of 1 atmosphere, a mixture of two metals (A and B) has the three phases α, β, and γ in equilibrium. Can the temperature be changed and still have the α, β, and γ phases in equilibrium?
Definition
 No (this equilibrium lies on isotherm)
Term
 At a pressure of 1 atmosphere, a mixture of two metals (A and B) has the two phases α and β equilibrium at the selected temperature (T). Can the chemical composition of the α phase be changed by adding more A-type atoms at temperature (T)?
Definition
 No (at constant temperature, cannot change composition)
Term
 In a(n) _____, liquid transforms to two solids α and β.
Definition
 eutectic reaction
Term
 In a(n) ____, one solid γ phase transforms to two solids α and β.
Definition
 eutectoid reaction
Term
 In a(n) _____, one solid α phase and a liquid phase react to form one solid phase β.
Definition
 peritectic reaction
Term
 In a(n) _____, two solid phases α and γ react to form one solid phase β.
Definition
 peritectoid reaction
Term
 The microstructure of the grains of solid α and β phases that form in the lead-tin eutectic reaction is ____ or ____ of the α and β phases.
Definition
 plates, layers
Term
 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 _____ of A and B should form.
Definition
 compound
Term
 The Ga-As phase diagram has a compound GaAs (γ-phase) that is a single vertical line at 50 atomic % As. Can γ-phase be produced that has 55 atomic % As?
Definition
 No
Term
 An ____ can have a wider region of possible compositions than does an intermediate compound.
Definition
 intermediate phase
Term
 When an intermediate phase melts with no change in chemical composition, this is a(n) _____.
Definition
 congruent melting point
Term
 In the aluminum-nickel phase diagram in Figure 5.15, what is the reaction type that leads to the formation of Al3Ni at 854°C?
Definition
 Peritectic
Term
 A(n) ____ is when one liquid transforms to another liquid and a solid upon cooling.
Definition
 monotectic reaction
Term
 In polymer blends, the enthalpy of interaction is determined from the experimentally determined _____.
Definition
 interaction parameter
Term
 If an iron-0.77 % C steel is very SLOWLY cooled from 800°C to room temperature, the expected microstructure is described as ____.
Definition
 pearlite
Term
 Pearlite microstructure
Definition
 γ --> α + Fe3C (slowly cooled)
Term
 If an iron-0.77 % C steel is very RAPIDLY cooled from 800°C to room temperature, the expected microstructure is described as ____.
Definition
 martensite
Term
 Occurs by deformation of a crystal rather than diffusion of atoms.
Definition
 Martensite phase
Term
 If as-quenched martensite is heated to 500 C for one hour, it is then ____.
Definition
 tempered martensite
Term
 The distortion of the FCC unit cell to a tetragonal unit cell after quenching a carbon steel from 800 C to room temperature is the ____.
Definition
 Bain distortion
Term
 For a martensitic transformation to be reversible there cannot be the production of _____ to accommodate strain.
Definition
 dislocations
Term
 In the shape-memory effect in metals, the martensitic transformation must be _____.
Definition
 reversible
Term
 In a reversible martensitic transformation, the GFE of the transformation is equal to _____.
Definition
 zero
Term
 True or False: For a blend of LCMs, if the enthalpy of mixing is +, polymers should mix in the liquid at all temps above melting.
Definition
 False
Term
 At the equilibrium melting temperature of a solid, if solid --> liquid, the change in GFE is ___.
Definition
 zero
Term
 At a temperature below the melting temperature of a solid, if liquid ---> solid, change in GFE is ___.
Definition
 negative
Term
 Which of the following is NOT true about nucleation and growth transformation from liquid --> solid?(a.) The transformation rate continuously increases with the amount of super-cooling(b) The transformation rate is equal to 0 at the equilibrium temperature.(c) The transformation rate goes to 0 at temperatures approaching 0 kelvin.(d) The transformation rate reaches a maximum at a temperature between the equilibrium temperature and 0 kelvin.
Definition
 The transformation rate continuously increases with the amount of super-cooling.
Term
 For a mixture 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?(a) If the temperature is changed, the composition of the α, β, and liquid phases changes. (b) The composition of the α phase is changed by adding more A-type atoms.(c) The composition of the liquid phase is changed by adding more A-type atoms.(d) Nothing can be changed.
Definition
 Nothing can be changed
Term
 Two phases α and β are in equilibrium, and they are made of A-type and B-type atoms. Which of the following statements is true?(a) The Gibbs free energies of the α and β phases are equal.(b) The chemical potentials of the A-type atoms in the α and β phases are equal.(c) The Gibbs free energies of the α and β phases are equal to 0.(d) The chemical potentials of the A-type and B-type atoms in the α-phase are equal.
Definition
 The chemical potentials of the A-type atoms in the α and β phases are equal.
Term
 Which of the following is not necessary for a continuous-solid solution?(a) Similar atomic numbers.(b) Atomic radii differ by less than 15%. (c) The same crystal structure.(d) A similar electronegativity.
Definition
 similar atomic numbers
Term
 Which of the following best describes the microstructure resulting from a eutectic reaction?(a) Alternating grains of α and β-phases.(b) Grains of the α-phase with precipitate particles of the β-phase.(c) A volume with only α-phase grains and another volume with only β-phase grains.(d) The grains contain alternating plates or rods of the α and β phases.
Definition
 The grains contain alternating plates or rods of the α and β phases.
Term
 Which of the following is a eutectoid reaction?
Definition
 γ --> α + β
Term
 Iron with 0.20% carbon is a(n) _____.
Definition
 hypoeutectoid steel (less than 0.77% C)
Term
 Bainite is formed by ______, then ______, then _____ with a eutectoid composition carbon steel starting at 800 C.
Definition
 Quench to 500 C, hold for 100 seconds, cool to room temperature
Term
 The highest-strength carbon steels with some ductility have a microstructure described as...
Definition
 tempered martensite
Term
 You are asked to design a metal alloy for use in salt water. The most important design parameter is corrosion resistance followed by other mechanical properties such as yield strength. It is known that dissimilar metals in contact in salt water can result in corrosion of one of the materials. What type of metal alloy phase diagrams should you consider first for this application?
Definition
 Continuous solid solution
Term
 You are asked to design a metal alloy for a high temperature application. What type of metal alloy phase diagrams should you consider first for this application?
Definition
 Compound formation
Term
 You are asked to design a metal alloy for a part with a room temperature application. The part is to be made by casting the metal into shape. When casting the part, liquid metal is poured into a mold that has a cavity with the shape of the part. To reduce cost by conserving energy and to utilize an inexpensive furnace that does not have a high temperature capability, it is desired that the metal alloy not have a high melting temperature. What type of metal alloy phase diagrams should you consider first for this part?
Definition
 eutectic
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