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73 Cards in this Set
- Front
- Back
The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.
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Diffusion
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What quantities are materials dependent values (depends on which material you are discussing)?
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Pre-exponential coefficiant
Activation Energy for diffusion |
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γ-iron (FCC) at 900°C has a larger diffusion coefficient, for the self-diffusion of iron, than α-iron (BCC) at 900°C.
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False. The atomic packing factor is greater for FCC FE meaning that there are more interstitial spaces available in the BCC FE. Therefore, motion of interstitial atoms moves more easily.
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What do we call the energy required to initiate a reaction such as diffusion?
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Activation energy.
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What do we call the diffusion mechanism wherein net atomic migration is from a lattice site to an adjacent vacancy.
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Vacancy Diffusion
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On the basis of diffusion, why are integrated circuits typically made of aluminum (compared to Au, Ag & Cu)?
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Less interconnect aluminum atoms diffuse into the silicon.
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Gold and silver form a substitutional FCC alloy. The mechanism by which silver diffuses within gold is called:
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Vacancy diffusion
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What is the driving force for diffusion?
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Concentration Gradient
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Interstitial diffusion is normally more rapid than vacancy diffusion because:
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(1) interstitial atoms, being smaller, are more mobile; (2) the probability of an empty adjacent interstitial site is greater than for a vacancy adjacent to a host atom.
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What do we call the impetus behind a reaction, such as diffusion, grain growth, or a phase transformation.
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Driving Force
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A diffusion mechanism whereby atomic motion is from interstitial site to interstitial site
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Interstitial Diffusion
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What is the term used for defining mass flow through and perpendicular to a unit cross sectional area of solid per unit time?
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Diffusion Flux
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What is the diffusion condition for which there is no net accumulation or depletion of diffusion species (where the diffusion flux is independent of time).
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Steady-state diffusion
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What is the process by which the surface carbon concentration of a ferrous alloy is increased by diffusion from the surrounding environment.
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Carburizing
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True or False: Metal A has a greater activation energy?
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True
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True or False: the activation energy for diffusion depends on temperature?
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False
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What is the ability of a material to absorb energy and plastically deform before fracturing.
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Toughness
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True or False: Elastic deformation is permanent and non-recoverable.
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False
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True or False:
Plastic deformation is non-permanent and recoverable. |
False
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True or False: At the atomic level, during elastic deformation, bonds are breaking?
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False
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True or False
Brittle metals are normally tougher than ductile ones. |
False
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Dislocation motion occurs within a crystalline material during during what type of deformation?
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Plastic
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True or False:
Poisson's ratio is defined as the ratio of the lateral and axial strains. |
True
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Hooke's law applies to which region of the stress strain curve?
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Elastic
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True or False:
Ductility is a measure of the degree to which a material will plastically deform by the time fracture occurs. |
True
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True or False:
Yield strength is the stress at the maximum on the engineering stress-strain curve. |
False
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Which hypothetical material is the stiffest?
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E
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Which hypothetical material exhibits the greatest ductility?
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B
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True or False:
Toughness is the capacity of a material to absorb energy when it is deformed elastically and then, upon loading, to have this energy recovered. |
False
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What are three factors that should be considered in designing a test to assess the mechanical characteristics of materials for
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Environmental conditions, load duration, and the nature of the applied load (tension, compressional, shear)
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What does a material that undergoes ductile fracture show?
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necking
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True or False:True stress is defined as the instantaneous applied load divided by the instantaneous cross-sectional area.
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True
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True or False:To strengthen an alloy, dislocation motion must be impeded (assuming the material has defects).
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True
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True or False:Recrystallization can happen to a metal or an alloy that has been plastically deformed and then heated.
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True
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Would you expect it to be possible for ceramic materials to experience recrystallization?
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No
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True or False:Metals such as lead and tin do not strain harden at room temperature.
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True
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For a metal or alloy that has been plastically deformed and then annealed what happens to ductility, grain size, tensile strength, and total number of grains?
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Ductility? Increase; Tensile strength? Decreases; Grain Size? Increases; Total number of grains? Decreases
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What does a slip system consist of?
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A slip system consists of a crystallographic plane, and, within that plane, a direction along which dislocation motion (or slip) occurs.
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What is the primary slip system for a BCC crystal?
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110 plane in the -111 direction
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True or False: Most metals strain harden at room temperature?
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True
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What is the Hall-Petch Equation used for?
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Used to determine Yield strength from the average grain size.
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True or False:
The critical resolved shear stress is the value of resolved shear stress at which yielding begins; it is a property of the material. |
True
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True or False:
Addition of substitutional components into a metal will weaken the metal (this is called solid-solution strengthening). |
False
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True or False:The hardness measured from an indentation that is positioned close to a preexisting indentation will be higher than if it were positioned further away.
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True
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True or False: Defects in a crystal can slow dislocation motion; this is how strain hardening weakens an alloy.
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False
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True or False:
It is possible for two screw dislocations of opposite sign to annihilate one another if their dislocation lines are parallel. |
True
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True or False:Cold working, work hardening and strain hardening all refer to the phenomena by which a ductile metal becomes harder as it is plastically deformed.
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True
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True or False:
In general, the ways to strengthen an alloy relies on increasing the ease with which slip occurs in the alloy. |
False
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Can a cold-worked metal can regain its mechanical properties through heat treatment?
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Yes
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True or False:
In general, for metals, as grain size increases the yield strength increases. |
False
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True or False:
Defects in a crystal can slow dislocation motion; this is how strain hardening strengthens an alloy. |
True
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True or False:
Edge, screw and mixed dislocations move (slip) in response to tensile stresses applied along a slip plane and in a slip direction. |
False
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Can a cold worked metal ever regain its mechanical properties?
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Yes
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Can recrystallization happen to a metal or an alloy that has been elastically deformed and then heated.
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No
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True or False: Cold working, work hardening and strain hardening all refer to the phenomena by which a ceramic becomes harder as it is plastically deformed.
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False
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True or False:
Edge, screw and mixed dislocations move (slip) in response to shear stresses applied along a slip plane and in a slip direction. |
True
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True or False:
Addition of substitutional components into a metal will strengthen the metal (this is called solid-solution strengthening). |
True
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Slip is where elastic deformation occurs within a plane.
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False
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Would you expect a crystalline ceramic material to strain harden at room temperature?
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No; because ceramics are brittle and cannot plastically deform.
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Factors that may lead to scatter in fatigue life data include:
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Variation in mean stress, specimen fabrication and surface preparation, specimen alignment and test apparatus, metallurgic variables, variation in test cycle frequency.
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The type of fracture where crack propagation is along grain boundaries is termed:
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Intergranular
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True or False:
Creep results from cyclic loading |
False
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True or False:A material’s tendency to exhibit creep decreases with increasing temperature.
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False
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The type of fracture where the crack passes through the grains, is termed:
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Transgranular
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When designing structures (that are subject to stresses) sharp corners should be avoided because they act as points of stress concentration, or "stress raises."
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True
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For metal alloys, select three metallurgical/processing techniques that enhance creep resistance:
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dispersion strengthening by using insoluble second phase, solid solution alloying, increasing the grain sized or producing a grain structure with preferred orientation.
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True or false:
A material’s tendency to exhibit creep increases with increasing temperature. |
True
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Fatigue results from cyclic loading?
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True
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The term that describes brittle crack propagation corresponding to the successive and repeated breaking of atomic bonds along specific crystallographic planes.
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Cleavage
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True or False:
Inset square edges are places that can initiate creep cracks. |
False
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Fatigue strength and fatigue life are parameters used to characterize the fatigue behavior of metals and alloys.
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True
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Some low strength steel alloys have a ductile-to-brittle transition which suggests:
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The alloy changes to a brittle behavior with decreasing temperature.
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Cup and Cone fractures are usually associated with what type of fracture?
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Ductile
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