metal – designation & properties r. lindeke engr. 2110 introduction to materials for engineers
TRANSCRIPT
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Metal – Designation & Properties
R. Lindeke
Engr. 2110
Introduction to Materials for Engineers
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Adapted from Fig. 9.24,Callister 7e. (Fig. 9.24 adapted from Binary Alloy Phase Diagrams, 2nd ed.,Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Materials Park, OH, 1990.)
Adapted from Fig. 11.1, Callister 7e.
Taxonomy of MetalsMetal Alloys
Steels
Ferrous Nonferrous
Cast Irons Cu Al Mg Ti<1.4wt%C 3-4.5wt%CSteels
<1.4 wt% CCast Irons3-4.5 wt% C
Fe3C
cementite
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
austenite
+L
+Fe3Cferrite
+Fe3C
+
L+Fe3C
(Fe) Co , wt% C
Eutectic:
Eutectoid:0.76
4.30
727°C
1148°C
T(°C) microstructure: ferrite, graphite cementite
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Alloy Taxonomy – (FerrousFocus!)
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Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 7e.
Steels
Low Alloy High Alloy
low carbon <0.25 wt% C
Med carbon0.25-0.6 wt% C
high carbon 0.6-1.4 wt% C
Uses auto struc. sheet
bridges towers press. vessels
crank shafts bolts hammers blades
pistons gears wear applic.
wear applic.
drills saws dies
high T applic. turbines furnaces V. corros. resistant
Example 1010 4310 1040 4340 1095 4190 304
Additions noneCr,V Ni, Mo
noneCr, Ni Mo
noneCr, V, Mo, W
Cr, Ni, Mo
plain HSLA plainheat
treatableplain tool
austenitic stainless
Name
Hardenability 0 + + ++ ++ +++ 0TS - 0 + ++ + ++ 0EL + + 0 - - -- ++
increasing strength, cost, decreasing ductility
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-LOW-CARBON STEEL ~<0.25%C•Unresponsive to heat treatment•Consist of ferrites and pearlite•Relatively soft and weak•Relatively ductile and tough•Weldable and machinable•Economical amongst all steel
-High Strength Low Alloy Steel-Alloying up to 10%-Increase corrosion properties-Higher strength
SAE – Society of Automotive engineersAISI- American Iron and Steel InstituteASTM- American Society for Testing and MaterialsUNS- Unified Numbering System
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MEDIUM CARBON STEELS – 0.25-0.6 wt%C•Heat treated by austenizing, quenching, and then tempering to improve their mechanical properties. Most often utilized in tempered condition with tempered martensite microsture.•Low hardenability can be heat treated only in very thin sections and with rapid quenching
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High Carbon steels: 0.60-1.4 wt%C – hardest, strongest, least ductileAlways used in hardened/tempered condition – wear and indentation resistantTool/die steels contain high Carbon and Chromium, Vanadium, tungsten and molybdenum Carbides
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Corrosion resistant Cr of at least 11 wt%
Three classes-Martensitic – heat treated (Q&T), Magnetic-Ferritic – not heat treated, Magnetic-Austenitic – heat treatable (PH), Non-magnetic & most corrosion resistant
Stainless Steel
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CAST IRONS – Carbon > 2.14 wt. %C , usually 3-4.5wt%CComplete Melting 1150 oC-1300 oC
Gray, White, Nodular, malleable
Silicon > 1%, slower cooling rates during solidification
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Types of Cast IronGray iron• graphite flakes
• weak & brittle under tension
• stronger under compression
• excellent vibrational dampening
• wear resistant
Ductile iron• add Mg or Ce
• graphite in nodules not flakes
• matrix often pearlite - better ductility
Adapted from Fig. 11.3(a) & (b), Callister 7e.
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Types of Cast IronWhite iron• <1wt% Si so harder but
brittle• more cementite
Malleable iron• heat treat at 800-900ºC• graphite in rosettes• more ductile
Adapted from Fig. 11.3(c) & (d), Callister 7e.
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Production of Cast Iron
Adapted from Fig.11.5, Callister 7e.
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Based on discussion and data provided in Section 11.3, Callister 7e.
Nonferrous Alloys
NonFerrous Alloys
• Al Alloys-lower : 2.7g/cm3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct.
aircraft parts & packaging)
• Mg Alloys-very low : 1.7g/cm3 -ignites easily -aircraft, missiles
• Refractory metals-high melting T -Nb, Mo, W, Ta• Noble metals
-Ag, Au, Pt -oxid./corr. resistant
• Ti Alloys-lower : 4.5g/cm3
vs 7.9 for steel -reactive at high T -space applic.
• Cu AlloysBrass: Zn is subst. impurity (costume jewelry, coins, corrosion resistant)Bronze : Sn, Al, Si, Ni are subst. impurity (bushings, landing gear)Cu-Be: precip. hardened for strength
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Copper Alloys
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Aluminum Alloys
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Additions to Cu and Al alloy Designations
Temper designation scheme for alloys: a letter and possibly a one- to three-digit number:
F, H, and O represent, respectively, the as-fabricated, strain hardened, and annealed states.
T3 means that the alloy was solution heat treated, cold worked, and then naturally aged (age hardened).
T6 means that the alloy was solution heat treated followed by artificial aging.
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Magnesium Alloys
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Titanium Alloys
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Metal Fabrication
• How do we fabricate metals?– Blacksmith - hammer (forged)– Molding - cast
• Forming Operations – Rough stock formed to final shape
Hot working vs. Cold working• T high enough for • well below Tm
recrystallization • work hardening
• Larger deformations • smaller deformations
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FORMING
roll
AoAd
roll
• Rolling (Hot or Cold Rolling) (I-beams, rails, sheet & plate)
Ao Ad
force
dieblank
force
• Forging (Hammering; Stamping) (wrenches, crankshafts)
often atelev. T
Adapted from Fig. 11.8, Callister 7e.
Metal Fabrication Methods - I
ram billet
container
containerforce
die holder
die
Ao
Adextrusion
• Extrusion (rods, tubing)
ductile metals, e.g. Cu, Al (hot)
tensile force
AoAddie
die
• Drawing (rods, wire, tubing)
die must be well lubricated & clean
CASTING JOINING
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FORMING CASTING JOINING
Metal Fabrication Methods - II
• Casting- mold is filled with liquid metal– metal melted in furnace, perhaps alloying
elements added. Then cast in a mold – most common, cheapest method– gives good reproduction of shapes– weaker products, internal defects– good option for brittle materials or microstructures
that are cooling rate sensitive
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plasterdie formedaround waxprototype
• Sand Casting (large parts, e.g., auto engine blocks)
• Investment Casting (low volume, complex shapes e.g., jewelry, turbine blades)
Metal Fabrication Methods - II
wax
• Die Casting (high volume, low T alloys)
• Continuous Casting (simple slab shapes)
molten
solidified
FORMING CASTING JOINING
Sand Sand
molten metal
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CASTING JOINING
Metal Fabrication Methods - III
• Powder Metallurgy (materials w/low ductility)
pressure
heat
point contact at low T
densification by diffusion at higher T
area contact
densify
• Welding (when one large part is impractical)
• Heat affected zone: (region in which the microstructure has been changed).
Adapted from Fig. 11.9, Callister 7e.(Fig. 11.9 from Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), 1981.)
piece 1 piece 2
fused base metal
filler metal (melted)base metal (melted)
unaffectedunaffectedheat affected zone
FORMING
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Annealing: Heat to Tanneal, then cool slowly.
Based on discussion in Section 11.7, Callister 7e.
Thermal Processing of Metals
Types of Annealing
• Process Anneal: Negate effect of cold working by (recovery/ recrystallization)
• Stress Relief: Reduce stress caused by:
-plastic deformation -nonuniform cooling -phase transform.
• Normalize (steels): Deform steel with large grains, then normalize to make grains small.
• Full Anneal (steels): Make soft steels for good forming by heating to get , then cool in furnace to get coarse P.
• Spheroidize (steels): Make very soft steels for good machining. Heat just below TE & hold for
15-25 h.
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a) Annealing
b) Quenching
Heat Treatments
c)
c) Tempered Martensite
Adapted from Fig. 10.22, Callister 7e.
time (s)10 10 3 10 510 -1
400
600
800
T(°C)
Austenite (stable)
200
P
B
TE
0%
100%50%
A
A
M + A
M + A
0%
50%
90%
a)b)
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Hardenability--Steels• Ability to form martensite• Jominy end quench test to measure hardenability.
• Hardness versus distance from the quenched end.
Adapted from Fig. 11.11, Callister 7e. (Fig. 11.11 adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.)
Adapted from Fig. 11.12, Callister 7e.
24°C water
specimen (heated to phase field)
flat ground
Rockwell Chardness tests
Har
dnes
s, H
RC
Distance from quenched end
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• The cooling rate varies with position.
Adapted from Fig. 11.13, Callister 7e. (Fig. 11.13 adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and Cooling Transformation Diagrams, American Society for Metals, 1977, p. 376.)
Why Hardness Changes W/Position
distance from quenched end (in)Ha
rdn
ess
, H
RC
20
40
60
0 1 2 3
600
400
200A M
A
P
0.1 1 10 100 1000
T(°C)
M(start)
Time (s)
0
0%100%
M(finish) Martensite
Martensite + Pearlite
Fine Pearlite
Pearlite
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Hardenability vs Alloy Composition• Jominy end quench results, C = 0.4 wt% C
• "Alloy Steels" (4140, 4340, 5140, 8640) --contain Ni, Cr, Mo (0.2 to 2wt%) --these elements shift the "nose". --martensite is easier to form.
Adapted from Fig. 11.14, Callister 7e. (Fig. 11.14 adapted from figure furnished courtesy Republic Steel Corporation.)
Cooling rate (°C/s)
Har
dne
ss, H
RC
20
40
60
100 20 30 40 50Distance from quenched end (mm)
210100 3
4140
8640
5140
1040
50
80
100
%M4340
T(°C)
10-1 10 103 1050
200
400
600
800
Time (s)
M(start)M(90%)
shift from A to B due to alloying
BA
TE
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• Effect of quenching medium:
Mediumairoil
water
Severity of Quenchlow
moderatehigh
Hardnesslow
moderatehigh
• Effect of geometry: When surface-to-volume ratio increases: --cooling rate increases --hardness increases
Positioncentersurface
Cooling ratelowhigh
Hardnesslowhigh
Quenching Medium & Geometry
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0 10 20 30 40 50wt% Cu
L+L
+L
300
400
500
600
700
(Al)
T(°C)
composition range needed for precipitation hardening
CuAl2
A
Adapted from Fig. 11.24, Callister 7e. (Fig. 11.24 adapted from J.L. Murray, International Metals Review 30, p.5, 1985.)
Precipitation Hardening• Particles impede dislocations.• Ex: Al-Cu system• Procedure:
Adapted from Fig. 11.22, Callister 7e.
--Pt B: quench to room temp.--Pt C: reheat to nucleate small crystals within crystals.
• Other precipitation systems: • Cu-Be • Cu-Sn • Mg-Al
Temp.
Time
--Pt A: solution heat treat (get solid solution)
Pt A (sol’n heat treat)
B
Pt B
C
Pt C (precipitate Consider: 17-4 PH St. Steel and Ni-Superalloys too!
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Effect of time at
Temperature during
Precipitation Hardening