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PRECIPITATION HARDENING. • Particles impede dislocations. • Ex: Al-Cu system • Procedure: -- Pt A : solution heat treat (get a solid solution) -- Pt B : quench to room temp. --Pt C: reheat to nucleate small q crystals within a crystals. - PowerPoint PPT Presentation
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Chapter 11-16
• Particles impede dislocations.• Ex: Al-Cu system• Procedure: --Pt A: solution heat treat (get solid solution) --Pt B: quench to room temp. --Pt C: reheat to nucleate small crystals within crystals.• Other precipitation systems: • Cu-Be • Cu-Sn • Mg-Al
Pt A (sol’n heat treat)
Pt B
Pt C (precipitate )
Temp.
Time
Adapted from Fig. 11.22, Callister 6e. (Fig. 11.22 adapted from J.L. Murray, International Metals Review 30, p.5, 1985.)
Adapted from Fig. 11.20, Callister 6e.
PRECIPITATION HARDENING
300
400
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0 10 20 30 40 50wt%Cu(Al)
L+L
+L
T(°C)
A
B
C
composition range needed for precipitation hardening
CuAl2
Chapter 11-16
PRECIPITATION HARDENING
Chapter 11-17
• 2014 Al Alloy:
• TS peaks with precipitation time.• Increasing T accelerates process.
• %EL reaches minimum with precipitation time.
Adapted from Fig. 11.25 (a) and (b), Callister 6e. (Fig. 11.25 adapted from Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th ed., H. Baker (Managing Ed.), American Society for Metals, 1979. p. 41.)
PRECIPITATE EFFECT ON TS, %EL
precipitation heat treat time (h)
tensi
le s
trength
(M
Pa)
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2001min 1h 1day 1mo1yr
204°C
149°C
non-
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man
y sm
all
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EL
(2in
sam
ple
)10
20
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0 1min 1h 1day 1mo1yr
204°C 149°C
precipitation heat treat time (h)
Chapter 11-18
• Peak-aged --avg. particle size = 64b --closer spaced particles efficiently stop dislocations.
Simulation courtesyof Volker Mohles,Institut für Materialphysik der Universitåt, Münster, Germany (http://www.uni-munster.de/physik/MP/mohles/). Used with permission.
SIMULATION: DISLOCATION MOTION PEAK AGED MATERIAL
Chapter 11-19
• Over-aged --avg. particle size = 361b --more widely spaced particles not as effective.
Simulation courtesyof Volker Mohles,Institut für Materialphysik der Universitåt, Münster, Germany (http://www.uni-munster.de/physik/MP/mohles/). Used with permission.
SIMULATION: DISLOCATION MOTIONOVERAGED MATERIAL
Chapter 11-20
• Steels: increase TS, Hardness (and cost) by adding --C (low alloy steels) --Cr, V, Ni, Mo, W (high alloy steels) --ductility usually decreases w/additions.• Non-ferrous: --Cu, Al, Ti, Mg, Refractory, and noble metals.• Fabrication techniques: --forming, casting, joining.• Hardenability --increases with alloy content.• Precipitation hardening --effective means to increase strength in Al, Cu, and Mg alloys.
SUMMARY