Metal – Designation & Properties

R. Lindeke

Engr. 2110

Introduction to Materials for Engineers

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

Alloy Taxonomy – (FerrousFocus!)

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

-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

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

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

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

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

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.

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.

Production of Cast Iron

Adapted from Fig.11.5, Callister 7e.

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

Copper Alloys

Aluminum Alloys

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.

Magnesium Alloys

Titanium Alloys

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

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

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

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

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

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.

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)

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

• 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

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

• 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

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!

Effect of time at

Temperature during

Precipitation Hardening