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 Metals Metal Alloys Steels FerrousNonferrous Cast Irons CuAlMgTi <1.4wt%C3-4.5wt%C Steels <1.4 wt% C Cast Irons wt% C Fe 3 C cementite L  austenite  +L+L  +Fe 3 C  ferrite  +Fe 3 C  +  L+Fe 3 C  (Fe) C o, wt% C Eutectic: Eutectoid: °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 carbon wt% C high carbon wt% C Usesauto 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 Additionsnone Cr,V Ni, Mo none Cr, Ni Mo none Cr, V, Mo, W Cr, Ni, Mo plainHSLAplain heat treatable plaintool austenitic stainless Name Hardenability TS EL 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 engineers AISI- American Iron and Steel Institute ASTM- American Society for Testing and Materials UNS- Unified Numbering System

MEDIUM CARBON STEELS – 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: wt%C – hardest, strongest, least ductile Always used in hardened/tempered condition – wear and indentation resistant Tool/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%C Complete Melting 1150 o C-1300 o C Gray, White, Nodular, malleable Silicon > 1%, slower cooling rates during solidification

Types of Cast Iron Gray 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 Iron White iron <1wt% Si so harder but brittle more cementite Malleable iron heat treat at ºC graphite in rosettes more ductile

Production of Cast Iron

Nonferrous Alloys NonFerrous Alloys Al Alloys -lower  : 2.7g/cm 3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct. aircraft parts & packaging) Mg Alloys -very low  : 1.7g/cm 3 -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/cm 3 vs 7.9 for steel -reactive at high T -space applic. Cu Alloys Brass : 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 T m recrystallization work hardening Larger deformations smaller deformations

FORMING roll A o A d Rolling (Hot or Cold Rolling) (I-beams, rails, sheet & plate) A o A d force die blank force Forging (Hammering; Stamping) (wrenches, crankshafts) often at elev. T Metal Fabrication Methods - I ram billet container force die holder die A o A d extrusion Extrusion (rods, tubing) ductile metals, e.g. Cu, Al (hot) tensile force A o A d die Drawing (rods, wire, tubing) die must be well lubricated & clean CASTINGJOINING

FORMINGCASTINGJOINING 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

plaster die formed around wax prototype 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 FORMINGCASTINGJOINING Sand molten metal

Schematic of the Investment Casting Process:

Typical Cast Microstructure: Composition of 356 Cast Aluminum: (SAE 356) Si Fe 0.2 Cu 0.2 Mn 0.1 Mg Cr 0.05 Ni 0.05 Zn 0.35 Pb 0.05 Ti 0.25 Sn 0.05 Al Balance

CASTINGJOINING 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 1piece 2 fused base metal filler metal (melted) base metal (melted) unaffected heat affected zone FORMING

Schematic of Powder Metallurgy Processes, Use for Metals and Ceramics

Properties: -- T m 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. GlassesClay products RefractoriesAbrasivesCementsAdvanced 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 (SiO 2 ) - Alumina (Al 2 O 3 ) 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) alumina + mullite + L mullite Liquid (L)(L) mullite +crystobalite + L alumina + L 3Al 2 O 3 -2SiO 2

tensile force A o A d 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 (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 blades oil drill bits Solutions: coated single crystal diamonds polycrystalline diamonds in a resin matrix. 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 ZrO 2 Principle: Make diffusion of ions fast for rapid response. Application: Sensors A Ca 2+ impurity removes aZr 4+ and a O 2- ion. Ca 2+ Approach: Add Ca impurity to ZrO 2 : -- increases O 2- vacancies -- increases O 2- diffusion rate reference gas at fixed oxygen content O 2- diffusion gas with an unknown, higher oxygen content - + voltage difference produced! sensor Operation: -- voltage difference produced when O 2- 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 ), "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: GLASS FORMING (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 PARTICULATE FORMING 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 bille t container force die holder die A o A d extrusion --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” GLASS FORMING PARTICULATE FORMING 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 Si 4+ Al 3+ - OH O 2- 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 shrinkage wet slippartially dry“green” ceramic Firing : --T raised to ( °C) --vitrification: liquid glass forms from clay and flows between SiO 2 particles. Flux melts at lower T. (From H.G. Brinkies, Swinburne University of Technology, Hawthorn Campus, Hawthorn, Victoria, Australia.) Si0 2 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 GLASS FORMING PARTICULATE FORMING CEMENTATION

Powder Pressing Sintering - 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-III GLASS FORMING PARTICULATE FORMING CEMENTATION

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: Si 3 N 4, SiC, & ZrO 2

Applications: Advanced Ceramics Ceramic Armor –Al 2 O 3, B 4 C, SiC & TiB 2 –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