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MEE 312 Test 2 Cards

TermDefinition
extensometer a device used for measuring change in length of sample to determine strain
carburization a heat treatment of steels to harden the surface using a gaseous source of carbon; the carbon diffusing into the surface makes the surface harder and more abrasion resistant
annealing a heat treatment that typically involves heating a metallic material to a high temperature for an extended period of time conducted with a view to lower the dislocation density and hence impart ductility
sintering a high temperature treatment used to join small particles, diffusion eventually fills in an remaining voids, the driving force is a reduction in the total surface area of the powder particles
stress relief anneal a low temperature annealing heat treatment designed to eliminate residual stresses introduced during deformation without reducing the strength of a col worked material
anelastic/viscoelastic a material in which the total strain developed has elastic and viscous components
Frank-Read Source a pinned dislocation that, under an applied stress, produces additional dislocations. This mechanism is at least partly responsible for strain hardening
fibertexture a preferred orientation of grains obtained during the wire drawing process (and other cold working processes); causes anisotropic behavior
shot peening a process in which metal spheres are shot at the component which leads to residual compressive stresses at the surface of the component to help improve fatigue life
columnar zone a region of elongated grains having a preferred orientation that forms as a result of competitive growth during solidification of a casting
equiaxed zone A region of randomly orientated grains in the center of a casting produced as a result of widespread nucleation
polyganized subgrain structure a subgrain structure produced in the early stages of annealing, a network of dislocations rearranged during heating
diffusion coefficient a temperature dependent coefficient related to the rate at which atoms, ions or other species diffuse; depends on temperature, the composition and the microstructure of the host material and also the concentration of diffusing species
creep a time dependent, permanent deformation at high temperatures, occurring at constant load or constant stress
bend test application of a force to the center of a bar that is supported on each end to determine the resistance of the material to a static or slowly applied load, used a lot for brittle materials
hot working deformation of a material above the recrystallization temperature; changes only shape, strength remains relatively unchanged
elastic deformation deformation of a material that is recovered instantaneously when the applied load is removed
volume diffusion diffusion of atoms through the interior of grains
interstitial diffusion diffusion of small atoms from one interstitial position to another in the crystal structure
surface diffusion diffusion of the atoms along surfaces such as cracks or particle surfaces
impact energy energy absorbed by a material, usually notched during fracture under the conditions of an impact test
necking local deformation causing a reduction in the cross sectional area of tensile specimen, many ductile materials show this behavior, the engineering stress begins to decrease at the onset of this
hardness test measures the resistance of a material through penetration of a sharp object, includes Rockwell, Brinell, Vickers, and Knoop
climb movement of dislocations perpendicular to slip plane by diffusion of atoms to or from the dislocation line
macrohardness overall bulk hardness of materials measured using loads greater than 2 Newtons, leaves a visible indention on the material
striations patterns seen on fractured surface of a fatigued sample, (very fine marks)
Young's modulus of elasticity slope of the linear part of the stress-strain curve in the elastic region; measure of the stiffness of a material, depends upon strength of interatomic bonds and composition, not strongly dependent on microstructure
residual stresses stresses introduced in a material during processing, can originate as a result of cold working
inoculation the addition of hetergeneous nuclei in a controlled manner to increase the number of grains in a casting
activation energy the energy required to cause a particular reaction to occur, in diffusion related to energy required to move an atom from one lattice site to another
Fick's First Law the equation relating the flux of atoms by diffusion coefficient and the concentration gradient
latent heat of fusion the heat evolved when a liquid solidifies, is related to the energy difference between the solid and the liquid
critical radius the minimum size that must be formed by atoms clustering together in the liquid before the solid particle is stable and begins to grow
fatigue life the number of cycles permitted at a particular stress before the material fails by fatigue
self diffusion the random movement of atoms with an essentially pure material, no net change in composition results
fracture toughness the resistance of a material to failure in the presence of a flaw
modulus of rupture the stress required to fracture a specimen in a bend test
DBTT the temperature below which a material behaves in a brittle manner in an impact test
percent elongation the total percentage increase in the length of a specimen during a tensile test
dendrite the treelike structure of the solid that grows when an undercooled liquid solidifies
undercooled when a liquid is below the equilibrium freezing temperature
characteristics of a ductile fracture a cup cone type failure with a dimpled surface and necking
hot working characteristic has a relatively rough surface finish
homogeneous nucleation requires what during solidification undercooling
impact loading materials are subject to high strain rates
anisotropic properties the properties resulting during plastic deformation in cold working grains. the grains rotate, causing certain crystallographic directions and planes to become aligned with the direction in which stress is applied
increase in the number of line defects the microstructural mechanism for strain hardening metals
vacancy diffusion is strongly dependent on what? temperature
electrical conductivity improves not a characteristic of cold working
the microstructural mechanism for strain hardening polymers stretching and aligning polymer chains
macrohardness (types of tests) Rockwell and Brinell
fatigue testing measures the material's resistance to what? cyclic loading
Why is understanding diffusion important? anything that affects diffusion will also affect material processing
fastest mechanism of diffusion vacancy
type of atom for which diffusion would occur fastest BCC
fast type of diffusion surface
mechanism most greatly affected by temperature vacancy
factors that affect diffusion temperature, mechanism and type of diffusion, crystal structure, bond type, and time
diffusion net flux of atoms, ions, or other species caused by temp and concentration gradients
diffusion couple combination of elements involved in diffusion studies
volume diffusion diffusion of atoms through the interior of grains
vacancy diffusion diffusion of atoms when an atoms leaves a regular lattice position to fill a vacancy in the crystal.
elastic strain fully and instanteously recoverable strain in a material
engineering stress applied load, or force, divided by the original cross section area of the material
engineering strain amount that a material deforms per unit length in a tensile test
fracture toughness the resistance of a material to failure in the presence of a flaw
impact toughness energy absorbed during fracture under the conditions of an impact test
modulus of resilience max elastic energy absorbed by a material when a load is applied
offset strain value a value of strain (0.002) used to obtain the offset yield stress value
offset yield strenght stress value that describes the stress that gives no more than a specified amount of plastic deformation
percent reduction in area total percentage decrease in the cross section area of a specimen during the tensile test
stiffness qualitative measure of the elastic deformation produced in a material
strain gage device used for measuring change in length and therefore strain
tensile strength stress that corresponds to the max load in a tensile test
endurance limit defines a stress below which a material will not fail in a fatigue test
fracture toughness the resistance of a material to failure in the presence of a flaw
toughness qualitative measure of the energy required to cause fracture of a material
cold working deformation of a material below the recrystallization temp. number of dislocations increase, causing the metal to be strengthened while changing its shape
drawing material is PULLED through an opening in a die
extrusion material is PUSHED through an opening in a die
recovery low temp annealing, eliminates residual stresses introduced during deformation without reducing strength of the cold-worked material. also called stress-relief anneal
recrystallization med-temp annealing heat treatment designed to eliminate all of the effects of strain hardening produced during cold working
strain hardening strengthening of a material by increasing number of dislocations by deformation, or cold working.
embryo tiny particle of solid that forms from the liquid as atoms cluster together
grain refinement addition of heterogeneous nuclei in a controlled manner to increase the number of grains in a casting
heterogeneous formation of a critically sized solid from the liquid on an impurity surface
homogeneous formation of a critically sized solid form the liquid by the clustering together of a large number of atoms at high undercooling
lamellar plate-like arrangement of crystals within a material
local solidification time time required for a particular location in a casting to solidify once nucleation has begun
nucleation the physical process by which a new phase is produced in a material
nuclei tiny particles of solid that form from the liquid as atoms cluster together
planar growth growth of a smooth solid-liquid inerface during solidification, no undercooling
recalescence increase in temperature of an undercooled liquid metal as a result of the liberation of heat during solidification
superheat pouring temp minus freezing temp
thermal arrest plateau on the cooling curve.
total solidification time time required for the casting to solidify completely after the casting has been poured
undercooling temp to which liquid metal must cool below the equil freezing temp before nucleation occurs
Created by: flyerbud