CHAPTER 13: METAL ALLOYS APPLICATIONS AND PROCESSING

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Transcript CHAPTER 13: METAL ALLOYS APPLICATIONS AND PROCESSING

TYPES AND APPLICATONS OF
MATERIALS
ISSUES TO ADDRESS...
• How are metal alloys classified and how are they used?
• How do we classify ceramics?
• What are some applications for ceramics?
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TAXONOMY OF METALS
Adapted from
Fig. 11.1,
Callister 6e.
Adapted from Fig. 9.21,Callister 6e.
(Fig. 9.21 adapted from Binary Alloy
Phase Diagrams, 2nd ed.,
Vol. 1, T.B. Massalski (Ed.-in-Chief),
ASM International, Materials Park,
OH, 1990.)
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STEELS
Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 6e.
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NONFERROUS ALLOYS
• Cu Alloys
• Al Alloys
Brass: Zn is subst. impurity -lower : 2.7g/cm 3
(costume jewelry, coins,
-Cu, Mg, Si, Mn, Zn additions
corrosion resistant)
-solid sol. or precip.
Bronze: Sn, Al, Si, Ni are
strengthened (struct.
subst. impurity
aircraft parts
(bushings, landing
& packaging)
gear)
• Mg Alloys
NonFerrous
Cu-Be:
-very low : 1.7g/cm 3
Alloys
precip. hardened
-ignites easily
for strength
-aircraft, missles
• Ti Alloys
-lower : 4.5g/cm 3
• Refractory metals
-high melting T
-Nb, Mo, W, Ta
vs 7.9 for steel
• Noble metals
-reactive at high T -Ag, Au, Pt
-oxid./corr. resistant
-space applic.
Based on discussion and data provided in Section 11.3, Callister 6e.
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TAXONOMY OF CERAMICS
Adapted from Fig. 13.1 and discussion
in Section 13.2-6, Callister 6e.
• Properties:
--Tmelt for glass is moderate, but large for other ceramics.
--Small toughness, ductility; large moduli & creep resist.
• Applications:
--High T, wear resistant, novel uses from charge neutrality.
• Fabrication
--some glasses can be easily formed
--other ceramics can not be formed or cast.
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APPLICATION: REFRACTORIES
• Need a material to use in high temperature furnaces.
• Consider Silica (SiO2) - Alumina (Al2O3) system.
• Phase diagram shows:
mullite, alumina, and crystobalite (made up of SiO2)
tetrahedra as candidate refractories.
2200
T(°C)
2000
3Al2O3-2SiO2
Liquid
(L)
1800
1400
0
alumina + L
mullite
+L
crystobalite
+L
1600
mullite
mullite
+ crystobalite
20
alumina
+
mullite
Adapted from Fig.
12.27, Callister 6e.
(Fig. 12.27 is adapted
from F.J. Klug and R.H.
Doremus, "Alumina
Silica Phase Diagram in
the Mullite Region", J.
American Ceramic
Society 70(10), p. 758,
1987.)
40
60
80
100
Composition (wt% alumina)
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APPLICATION: DIE BLANKS
• Die blanks:
--Need wear resistant properties!
die
Ad
die
Adapted from
Fig. 11.7,
Callister 6e.
Ao
Courtesy Martin Deakins, GE
Superabrasives,
Worthington, OH. Used with
permission.
tensile
force
• Die surface:
--4 mm polycrystalline diamond
particles that are sintered on to a
cemented tungsten carbide
substrate.
--polycrystalline diamond helps control
fracture and gives uniform hardness
in all directions.
Courtesy Martin Deakins, GE
Superabrasives,
Worthington, OH. Used with
permission.
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APPLICATION: CUTTING TOOLS
• Tools:
--for grinding glass, tungsten,
carbide, ceramics
--for cutting Si wafers
--for oil drilling
• Solutions:
oil drill bits
--manufactured single crystal
or polycrystalline diamonds
in a metal or resin matrix.
--optional coatings (e.g., Ti to help
diamonds bond to a Co matrix
via alloying)
--polycrystalline diamonds
resharpen by microfracturing
along crystalline planes.
blades
coated single
crystal diamonds
polycrystalline
diamonds in a resin
matrix.
Photos courtesy Martin Deakins,
GE Superabrasives, Worthington,
OH. Used with permission.
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APPLICATION: SENSORS
• Ex: Oxygen sensor: ZrO2
• Principle: Make diffusion of ions
fast for rapid response.
• Approach:
Add Ca impurity to:
--increase O2- vacancies
--increase O2- diffusion
• Operation:
--voltage difference
produced when
O2- ions diffuse
between external
and references
gases.
sensor
gas with an
reference
unknown, higher
gas at fixed
O2oxygen content
oxygen content
diffus
ion
+
-
voltage difference produced!
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SUMMARY
• 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
• Nonferrous:
-Cu, Al, Ti, Mg Refractory, and noble metals
• Basic categories of ceramics:
-Glasses
-Clay products
-Refactories
-Cements
-Advanced ceramics
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