Metal Ceramic and Glasses Designation & Processes

R. Lindeke

ME 2105

( Binary Alloy Phase Diagrams, 2nd ed.,Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Materials Park, OH, 1990.)

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 ferrite and pearlite•Relatively low strength•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 They contain primary 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

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

Production of Cast Iron

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

Specifics:

Additions to Al and Cu alloy Designations:

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

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

Schematic of the Investment Casting Process:

Typical Cast Microstructure:

Composition of 356 Cast Aluminum:

(SAE 356) Si 6.5 - 7.5

Fe 0.2 Cu 0.2 Mn 0.1

Mg 0.25 - 0.45 Cr 0.05 Ni 0.05 Zn 0.35 Pb 0.05 Ti 0.25 Sn 0.05

Al Balance

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).

(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

Schematic of Powder Metallurgy Processes, Use for Metals and Ceramics

• Properties: -- Tm for glass is moderate, but large for other ceramics. -- minimal 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.

Glasses Clay products

Refractories Abrasives Cements Advanced ceramics

-optical -composite reinforce -containers/ household

-whiteware -bricks

-bricks for high T (furnaces)

-sandpaper -cutting -polishing

-composites -structural

engine -rotors -valves -bearings

-sensors

Taxonomy of Ceramics

• Need a material to use in high temperature furnaces.• Consider the Silica (SiO2) - Alumina (Al2O3) system.

• Phase diagram shows: mullite, alumina, and crystobalite as candidate refractories.

(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.)

Application: Refractories

Composition (wt% alumina)

T(°C)

1400

1600

1800

2000

2200

20 40 60 80 1000

alumina +

mullite

mullite + L

mulliteLiquid

(L)

mullite + crystobalite

crystobalite + L

alumina + L

3Al2O3-2SiO2

tensile force

AoAddie

die

• Die blanks: -- Need wear resistant properties!

• Die surface: -- 4 m polycrystalline diamond particles that are sintered onto 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.

Adapted from Fig. 11.8 (d), Callister 7e. Courtesy Martin Deakins, GE

Superabrasives, Worthington, OH. Used with permission.

Application: Die Blanks

• Tools: -- for grinding glass, tungsten, carbide, ceramics -- for cutting Si wafers -- for oil drilling

bladesoil drill bits• Solutions:

coated singlecrystal diamonds

polycrystallinediamonds in a resinmatrix.

Photos courtesy Martin Deakins,GE Superabrasives, Worthington,OH. Used with permission.

Application: Cutting Tools

-- 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.

• Example: Oxygen sensor ZrO2

• Principle: Make diffusion of ions fast for rapid response.

Application: Sensors

A Ca2+ impurity

removes a Zr4+ and a

O2- ion.

Ca2+

• Approach: Add Ca impurity to ZrO2:

-- increases O2- vacancies

-- increases O2- diffusion rate

reference gas at fixed oxygen content

O2-

diffusion

gas with an unknown, higher oxygen content

-+voltage difference produced!

sensor• Operation: -- voltage difference produced when

O2- ions diffuse from the external surface of the sensor to the reference gas.

Alternative Energy – Titania Nano-Tubes"This is an amazing material architecture for water photolysis," says Craig Grimes, professor of electrical engineering and materials science and engineering. Referring to some recent finds of his research group (G. K. Mor, K. Shankar, M. Paulose, O. K. Varghese, C. A. Grimes, Enhanced Photocleavage of Water Using Titania Nanotube-Arrays, Nano Letters, vol. 5, pp. 191-195.2005 ), "Basically we are talking about taking sunlight and putting water on top of this material, and the sunlight turns the water into hydrogen and oxygen. With the highly-ordered titanium nanotube arrays, under UV illumination you have a photoconversion efficiency of 13.1%. Which means, in a nutshell, you get a lot of hydrogen out of the system per photon you put in. If we could successfully shift its bandgap into the visible spectrum we would have a commercially practical means of generating hydrogen by solar

energy.

Figure 11.2 Cookware made of a glass-ceramic provides good mechanical and thermal properties. The casserole dish can withstand the thermal shock of simultaneous high temperature (the torch flame) and low temperature (the block of ice). (Courtesy of Corning Glass Works.)

• Pressing:

GLASSFORMING

(adapted from C.J. Phillips, Glass: The Miracle Maker, Pittman Publishing Ltd., London.)

Ceramic Fabrication Methods-I

Gob

Parison mold

Pressing operation

• Blowing:

suspended Parison

Finishing mold

Compressed air

plates, dishes, cheap glasses

--mold is steel with graphite lining

• Fiber drawing:

wind up

PARTICULATEFORMING

CEMENTATION

Sheet Glass Forming

• Sheet forming – continuous draw– originally sheet glass was made by “floating”

glass on a pool of mercury – or tin

Modern Plate/Sheet Glass making:

Image from Prof. JS Colton, Ga. Institute of Technology

• Milling and screening: desired particle size• Mixing particles & water: produces a "slip"• Form a "green" component

• Dry and fire the component

ram billet

container

containerforce

die holder

die

Ao

Adextrusion--Hydroplastic forming: extrude the slip (e.g., into a pipe)

Ceramic Fabrication Methods-IIA

solid component

--Slip casting:

(from W.D. Kingery, Introduction to Ceramics, John Wiley and Sons, Inc., 1960.)hollow component

pour slip into mold

drain mold

“green ceramic”

pour slip into mold

absorb water into mold “green

ceramic”

GLASSFORMING

PARTICULATEFORMING

CEMENTATION

Commercial Clay Compositions

A mixture of components is used

(50%) 1. Clay mineral

(25%) 2. Filler – e.g. quartz (finely ground)

(25%) 3. Fluxing agent (Feldspar) – binds it together after sintering

aluminosilicates + K+, Na+, Ca+

• Clay is inexpensive• Adding water to clay -- allows material to shear easily along weak van der Waals bonds -- enables extrusion & slip casting

• Structure of Kaolinite Clay:

(adapted from W.E. Hauth, "Crystal Chemistry of Ceramics", American Ceramic Society Bulletin, Vol. 30 (4), 1951, p. 140.)

Features of a Slip

weak van der Waals bonding

charge neutral

charge neutral

Si4+

Al3+

-OHO2-

Shear

Shear

• Drying: layer size and spacing decrease.

(from W.D. Kingery, Introduction to Ceramics, John Wiley and Sons, Inc., 1960.)

Drying and Firing

Drying too fast causes sample to warp or crack due to non-uniform shrinkagewet slip partially dry “green” ceramic

• Firing: --T raised to (900-1400°C) --vitrification: liquid glass forms from clay and flows between SiO2 particles. Flux melts at lower T.

(From H.G. Brinkies, Swinburne University of Technology, Hawthorn Campus, Hawthorn, Victoria, Australia.)

Si02 particle

(quartz)

glass formed around the particle

micrograph of porcelain

70 m

Sintering: useful for both clay and non-clay compositions.• Procedure: -- produce ceramic and/or glass particles by grinding -- place particles in mold -- press at elevated T to reduce pore size.

• Aluminum oxide powder: -- sintered at 1700°C for 6 minutes.

(from W.D. Kingery, H.K. Bowen, and D.R. Uhlmann, Introduction to Ceramics, 2nd ed., John Wiley and Sons, Inc., 1976, p. 483.)

Ceramic Fabrication Methods-IIB

15 m

GLASSFORMING

PARTICULATEFORMING

CEMENTATION

Powder PressingSintering - powder touches - forms neck &

gradually neck thickens– add processing aids to help form neck– little or no plastic deformation

Uniaxial compression - compacted in single direction

Isostatic (hydrostatic) compression - pressure applied by fluid - powder in flexible envelope

Hot pressing - pressure + heat (HIP combines both)

• Produced in extremely large quantities.• Portland cement: -- mix clay and lime bearing materials -- calcinate (heat to 1400°C) -- primary constituents: tri-calcium silicate di-calcium silicate• Adding water -- produces a paste which hardens -- hardening occurs due to hydration (chemical reactions with the water).• Forming: done usually minutes after hydration begins.

Ceramic Fabrication Methods-IIIGLASS

FORMING PARTICULATE

FORMINGCEMENTATION

Applications: Advanced Ceramics

Heat Engines• Advantages:

– Run at higher temperature– Excellent wear &

corrosion resistance– Low frictional losses– Ability to operate without

a cooling system– Low density

• Disadvantages: – Brittle– Too easy to have voids-

weaken the engine– Difficult to machine

• Possible parts – engine block, piston coatings, jet engines

Ex: Si3N4, SiC, & ZrO2

Applications: Advanced Ceramics

• Ceramic Armor– Al2O3, B4C, SiC & TiB2

– Extremely hard materials • shatter the incoming projectile• energy absorbent material underneath

Applications: Advanced Ceramics

Electronic Packaging• Chosen to securely hold microelectronics &

provide heat transfer• Must match the thermal expansion coefficient of

the microelectronic chip & the electronic packaging material. Additional requirements include:– good heat transfer coefficient– poor electrical conductivity

• Materials currently used include:• Boron nitride (BN)• Silicon Carbide (SiC)• Aluminum nitride (AlN)

– thermal conductivity 10x that for Alumina– good expansion match with Si