Freedom is an elusive concept. Some men hold themselves prisoner even when they have the power to do as they please and go where they choose, while others are free in their hearts, even as shackles restrain them

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Freedom is an elusive concept. Some men hold
themselves prisoner even when they have the power
to do as they please and go where they choose,
while others are free in their hearts, even as
shackles restrain them -Zensunni wisdom
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With tiny precipitate particles
Why don't dislocs move thru precipitates? a.
complex structure - poorly defined slip
planes and/or b. slip planes wrongly oriented
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Solute atoms different size than solvent atoms
Crystal structure distorted slip planes less
well-defined Disloc movement restricted
Cu solid solutions
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Work hardening Solution hardening Precipitation
hardening Grain size reduction
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Oh, yeah.one more thing about dislocs
Ease of disloc motion depends on slip plane
orientation wrt applied stress direction
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Slip occurs only as a result of shear only
along slip plane in a slip direction
The greater the no. of slip systems, the greater
the probability some slip plane slip direction
correctly oriented
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Slip system slip plane slip direction
ccp - 12 slip systems hcp - 3 slip
systems
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Composition 52.5Ni 19Cr 3Mo 19Fe 0.4Al
5Nb-1Ti 0.04C
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Possibilities for strengthening 718
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52.5Ni Provides friendly matrix for alloying
elements
19Cr Oxidation and corrosion resistance, solid
solution strengthening
3Mo Solid solution strengthening, stabilizes
chromium oxide film, carbide formation for Hi
T strength
19Fe Solid solution strengthening
0.4Al Increases oxidation resistance, forms
strengthening pptates
5Nb-1Ti Form strengthening pptates
0.04C Carbide formation for creep resistance
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The primary strengthening phase for alloy 718 is
" with some contribution from '. The " is
coherent and has a body-centered-tetragonal
crystal structure, while ' has an ordered
face-centered-cubic crystal structure. The
stoichiometry of both can be represented as
Ni3(Nb,Ti,Al). The " and ' phases in alloy 718
are both metastable. The stable precipitate phase
is , which has an incoherent orthorhombic crystal
structure of Ni3(Nb,Ti). It forms as
intergranular lathes along (111) planes and/or at
grain boundaries.
ccp - 12 slip systems hcp - 3 slip
systems
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718 (Ni-18.5Fe-18Cr-5.3Nb-3Mo-0.9Ti-0.5Al-0.03C)
ccp - 12 slip systems hcp - 3 slip
systems