Term
| what is the order of products based on cooling rate starting with austenite |
|
Definition
| austenite, ferrite, pearlite, widmanstaaten, bainite, martensite |
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|
Term
| what qualifies as a grey cast iron |
|
Definition
high carbon/silicon percentage
upon slow cooling will achieve graphite flakes, eutectoid, then C is rejected to form proeutectoid and finally peralite grows |
|
|
Term
| what are the properties of grey cast irons and an application |
|
Definition
there is volume expansion so they are good for casting
brittle due to interconnected flakes
used as car cylinder heads |
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Term
| what qualifies as a spheroidal cast iron |
|
Definition
a type of grey cast iron
Mg or Ce is added which stops growth of graphite flaks so that spheres are made instead increasing toughness |
|
|
Term
| what are the properties of spheroidal cast irons and an application |
|
Definition
increased fracture toughness
manhole covers |
|
|
Term
| what qualifies as a white cast iron |
|
Definition
low C/Si content
Upon fast cool, cementite growths, once carbon is rejected more cementite grows and finally peralite is produced |
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|
Term
| what are the properties of white cast irons and an application |
|
Definition
they are hard and wear resistant
rolls for crushing mills |
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|
Term
| what are some steel alpha/ferrite stabilizers |
|
Definition
|
|
Term
| what are some steel gamma, austenite stabilizers |
|
Definition
|
|
Term
| what makes magnesium ideal |
|
Definition
| lightest engineering material*, forms a protective oxide, tough, conductive (thermally and electrically), high coefficient of thermal expansion, machinable*, hcp lattice parameters make it compatible with many other elements |
|
|
Term
| what are some applications of Mg based alloys |
|
Definition
cast is more popular than wrought (because it tends to have a low proof stress)
automobiles (strength/weight ratio)
sacrifical anode for bridges/ships |
|
|
Term
| disadvantages of Mg alloys |
|
Definition
highly susceptible to impurities
stress corrosion cracking/H-embrittling (Zr alloys are less prone)
its oxide speeds up
wrought must be heavily processed (hot worked with alternite tension and compression to form twins)
casting exhibits much porosity though cools faster and has less wear
instability at low pH |
|
|
Term
| Nomenclature for Mg Alloys |
|
Definition
alloying elements are identified by single letters
tempering modelled the same as Al |
|
|
Term
|
Definition
| subject to stress corrosion cracking |
|
|
Term
| What is the importance of adding Zr to Mg |
|
Definition
| most effective grain refiner therefore increases tensile properties however* not compatible with Si, Al, Mn, Fe therefore bad in steel crucibles |
|
|
Term
|
Definition
| greatly improve properties but are very expensive, increase castability, decrease porosity, increase tensile creep, increase corrosion, these are also solid-solution/precipitation hardeners |
|
|
Term
|
Definition
| improves catability, leads to microporosity, is a precipitation and solid-solution hardener |
|
|
Term
|
Definition
| increases creep resistance, controls Fe presence by forming new compounds, increases corrosion effects due to iron |
|
|
Term
| small* amounts of Zn in Mg alloys |
|
Definition
| increases metal flow and hence castability |
|
|
Term
|
Definition
| formation of Mg2Si at grain boundaries greatly hurts the overall properties of the material |
|
|
Term
| What is the Young's Modulus of steel |
|
Definition
|
|
Term
| What is the Young's modulus of Aluminium |
|
Definition
|
|
Term
| why are titanium alloys ideal |
|
Definition
chemically and thermally stable (high Tm, low coefficient of thermal expansion)
able to make many stable solid solutions
low density |
|
|
Term
| applications of titanium alloys |
|
Definition
|
|
Term
| what is the most desired titanium alloy |
|
Definition
|
|
Term
| What is the stipulation on e/a ratios for Ti alpha and beta stabilizers |
|
Definition
alpha: e/a<4
beat: otherwise |
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|
Term
| Features of Ti alpha alloys and some of the stabilizers |
|
Definition
Stabilizers: Al, O, N, C (tend to be interstitial)
low T, hcp, strong, anisotropic |
|
|
Term
| Features of beta isormorphous Ti alloys and some stabilizers |
|
Definition
high T, bcc, easy to form, heat treatable
Stabilizers: V, Nb, Mo, Si |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| Ti beta eutectic stabilizers |
|
Definition
|
|
Term
|
Definition
generally these have good hardenability
Sn, Zr |
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|
Term
| Properties of fully alpha Ti alloys |
|
Definition
resistant to plastic flow
low ductility/brittle/tough
high creep/corrosion resistance
low diffusion rates
subject to stress corrosion cracking (H)
tends to have equiaxed grains |
|
|
Term
| properties of near alpha Ti alloys |
|
Definition
higher operating tempeartures
higher creep resistance
some beta grains
may be bimodal or lamellar structure |
|
|
Term
| properties of fully beta Ti alloys and an application |
|
Definition
it may contain an omega phase which embrittles the material overall
allows for cold deformability
used for landing gear |
|
|
Term
| properties of alpha + beta ti alloys and an application |
|
Definition
hard to break (basket weave structure)
increased temperature stability
shows superplasticity
tanks for missles
airplane rotors |
|
|
Term
| what controls microstructure in Ti alloys |
|
Definition
alloy class/type
temperature/time
amount of deformation
cooling rate |
|
|
Term
| grain size in Ti alloys is controlled by... |
|
Definition
recrystallization temperature
recrystallization time
annealing
deformation |
|
|
Term
| What are some high temperature alloys |
|
Definition
| Ni, Co, v, cr, Nb, M, Ta, W, Graphite |
|
|
Term
| What are properties of high temperature alloys |
|
Definition
high Tm
reasonable strength at T of service
ability to be formed/manufactured
sufficient ductility at room Temrpature
resistance to oxidation (inherent or with coatings) |
|
|
Term
|
Definition
ideal because of their high Tm and FCC-stable structure
Applications: turbine blades
Major solutes: Al, Ti |
|
|
Term
|
Definition
gamma - FCC
gamma' - cubic P with the solute at corners
the gamma/gamma' interfacial energy is low therefore the system is stable |
|
|
Term
| What is the significance of recrystallization |
|
Definition
T-controls ggrain size and fraction of species
leads to equiaxed grains
determines amount and size of species
cooling rate determines lamellae size |
|
|
Term
| What is the importance of quench rate |
|
Definition
supersaturates system with vacancies which shorten/annihilate dislocations
decrease in QR increases ductility
high QR leads to increased strength and lamellar structure |
|
|
Term
| effects of deformation on alloys |
|
Definition
if rolled too much, recrystallization will not happen
rolling and solidfication lead to banding
deformation leads to texture |
|
|
Term
| conditions for superplasticity |
|
Definition
| dislocations originate and annihilate at the same rate |
|
|
Term
|
Definition
formation of stable carbides (Cr, Mo, W, Nb, V) increases wear resistance
applications: cutting tools, creep resistance |
|
|
Term
|
Definition
| heat to gamma, air cool for coarse structure |
|
|
Term
|
Definition
| heat to gamma, slow cool for cloarse pearlite leading to good machinability |
|
|
Term
|
Definition
| solution treat at high termpatures, quench, age to make a dispersion of precipiates in a matrix |
|
|
Term
|
Definition
one that can be used at very high temperatures >0.7Tm
creep and oxidation resistance are desired |
|
|
Term
|
Definition
precipitates (fine and uniform) to prevent dislocation mobility
if there are 2+ phases 1 should be fine to increase strength and 1 platelike to resist strain
|
|
|
Term
|
Definition
| reduces partitioning, removes eutectic, and controlls the precipiation of the elements |
|
|
Term
| importance of light metals |
|
Definition
a. High tensile strength, high modulus, high compressive yield strength, low density
b. Recyclable and long years of supply (though there tends to be expensive intial production and often alloying elements can not be removed)
c. Corrosoin resistance, electrical/thermal conductivity, machinability
d. Al, Mg and Ti are all in abundance (ocean, crust, etc.)
e. Growth mainly a result of transportation and aerospace industries
|
|
|
Term
| What are TTT diagrams used for |
|
Definition
| to illustrate the kinetics of phase formation |
|
|
Term
| Why do alloying elements change the properties of materials |
|
Definition
different T at which phases first nucleate
the rates of nucleation and growth change due to relative diffusion coefficients
relative stabilities of phases present are different |
|
|
Term
Upper bainite v. Lower bainite
features and applications |
|
Definition
|
|
Term
| what is tempering and how does it effect the properties of materials |
|
Definition
heating the material of interest to a temperature just below the eutectic temperature
allows for control of yield strength, ductility, and toughness (makes a material more usable) |
|
|
Term
martensite properties
effects of adding carbon |
|
Definition
tends to be hard and brittle because of the high internal strain energy
with increased carbon content, these values continue to increase because there is an increase in the c/a ratio
fine twins |
|
|
Term
|
Definition
| steel with the additon of Cr to increase corrosion resistance |
|
|
Term
| steel ferrite stabilizers |
|
Definition
| Cr and Si allow ferrite to exist at higher temperatures |
|
|
Term
| Steel austenite stabilizers |
|
Definition
|
|
Term
| Steel alloying elements that promote secondary hardening |
|
Definition
Cr, Mo, W, Nb, V
these form stable carbides in the steel |
|
|
Term
|
Definition
strength is based on precipitates
toughness is based on constituents
few alloying elements have significant solid solubility
cooling rate and grain refiners are very important |
|
|
Term
|
Definition
the addition of VERY small amounts of an alloying element that still manage to drastically change properties
|
|
|
Term
|
Definition
| leads to low density and reduces porosity |
|
|
Term
| importance of precipitate size in increasing strength |
|
Definition
if they are too fine dislocations can 'cut' them (underaged)
if they are too coarse, dislocations can 'bow' around them (overaged) |
|
|
Term
|
Definition
low density
high specific modulus
weldable
good fatigue and cryogenic toughness properties |
|
|
Term
|
Definition
1xxx-pure Al
2xxx-Al-Cu
6xxx-Mg, Si |
|
|
Term
|
Definition
relates grain size to yield strength
σy=σ0+kd-1/2 |
|
|
Term
why is pearlite lamellar
significance of the interfaces |
|
Definition
- partitioning is ideal but there is a competition between the number of interfaces and the distance carbon has to travel to reach cementite phases
- the interfaces control toughness
|
|
|
Term
|
Definition
|
|
Term
|
Definition
| effects the ductile/brittle transition |
|
|
Term
|
Definition
| increases corrosion resistance |
|
|
Term
|
Definition
|
|
Term
| properties of ferrite steel |
|
Definition
|
|
Term
| properties of austenite steels |
|
Definition
|
|
Term
| why is the TTT diagram C shaped |
|
Definition
high T, hard to nucleate
low T, hard to diffusive |
|
|
Term
| what methods can be used to measure transformations |
|
Definition
| microstructural evolution, volume change, XRD |
|
|
Term
| what is the effect of adding alloying elements to TTT diagrams |
|
Definition
| tends to shift TTT curves right because it takes longer for these atoms to diffusive |
|
|
Term
| why is pure aluminium not ideal |
|
Definition
low yield strength requires solid solution hardening
Mg is the most effective strengthener on a weight basis |
|
|
Term
|
Definition
intermetallic and stable (sulifdides, phosphates, etc.)
hard to get rid of and responsible for onset of cracks due to microstructural changes |
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|
