Chapter 11: Applications and Processing of Metal Alloys ISSUES TO ADDRESS... • How are metal alloys classified and what are their common applications? • What are some of the common fabrication techniques for metals? • What heat treatment procedures are used to improve the mechanical properties of both ferrous and nonferrous alloys?

Classification of Metal Alloys Adapted from Fig. 11.1, Callister & Rethwisch 9e. Ferrous Nonferrous _______ _________ Steels __________ ___________ Cast Irons <1.4wt%C 3-4.5 wt%C microstructure: ferrite, graphite/cementite Fe 3 C cementite 1600 1400 1200 1000 800 600 400 1 2 4 5 6 6.7 L γ austenite γ + L γ + Fe3C α ferrite α + Fe3C + L+ Fe3C δ (Fe) Co , wt% C Eutectic: Eutectoid: 0.76 4.30 727ºC 1148ºC T(ºC) Fig. 9.24, Callister & Rethwisch 9e. [Adapted from Binary Alloy Phase Diagrams, 2nd edition, Vol. 1, T. B. Massalski (Editor-in-Chief), 1990. Reprinted by permission of ASM International, Materials Park, OH.]

Steels Low Alloy High Alloy low carbon <0.25 wt% C Med carbon high carbon 0.6-1.4 wt% C plain HSLA heat treatable tool stainless Name Additions none Cr,V Ni, Mo Cr, Ni Mo Cr, V, Mo, W Cr, Ni, Mo Example 1010 4310 1040 43 40 1095 4190 304, 409 Hardenability + ++ +++ varies TS - + ++ varies EL + + - - -- ++ Uses auto bridges crank pistons wear drills high T struc. towers shafts gears applic. saws applic. sheet press. bolts wear dies turbines vessels hammers applic. furnaces increasing strength, cost, decreasing ductility blades Very corros. resistant Based on data provided in Tables 11.1(b), 13.2(b), 11.3, and 11.4, Callister & Rethwisch 9e.

Refinement of Steel from Ore Iron Ore _____ ______________ 3CO + Fe2O3 ® 2Fe +3CO2 C + O2 CO2 2CO CaCO3 CaO+CO2 CaO + SiO2 + Al2O3 slag purification reduction of iron ore to metal heat generation Molten iron BLAST FURNACE air layers of _____ and _________ gas refractory vessel

Ferrous Alloys Iron-based alloys • Steels • Cast Irons Nomenclature for steels (AISI/SAE) 10xx ___________________ 11xx Plain Carbon Steels (resulfurized for machinability) 15xx Mn (1.00 - 1.65%) 40xx Mo (0.20 ~ 0.30%) 43xx Ni (1.65 - 2.00%), Cr (0.40 - 0.90%), Mo (0.20 - 0.30%) 44xx Mo (0.5%) where xx is wt% C x 100 example: 1060 steel – plain carbon steel with 0.60 wt% C _______________________ >11% Cr • Steels • Cast Irons

Cast Irons Ferrous alloys with > ______________ more _________________________ Low melting – relatively easy to cast Generally brittle Cementite decomposes to ______ + _______ Fe3C  3 Fe (α) + C (____________) generally a slow process So phase diagram for this system is different (Fig 12.4)

Fe-C True Equilibrium Diagram 1600 1400 1200 1000 800 600 400 1 2 3 4 90 L γ + L  + Graphite Liquid + Graphite (Fe) C, wt% C 0.65 740°C T(°C) γ + Graphite 100 1153°C γ Austenite 4.2 wt% C α + γ Graphite formation promoted by __________ Cast irons have graphite Fig. 11.2, Callister & Rethwisch 9e. [Adapted from Binary Alloy Phase Diagrams, T. B. Massalski (Editor-in-Chief), 1990. Reprinted by permission of ASM International, Materials Park, OH.]

Types of Cast Iron _______ iron ___________________ Figs. 11.3(a) & (b), Callister & Rethwisch 9e. [Courtesy of C. H. Brady and L. C. Smith, National Bureau of Standards, Washington, DC (now the National Institute of Standards and Technology, Gaithersburg, MD] _______ iron ___________________ weak & brittle in tension stronger in compression excellent _________ dampening wear resistant ________ iron add Mg and/or Ce graphite as _______ not flakes matrix often pearlite – stronger but less ductile

Types of Cast Iron (cont.) Figs. 11.3(c) & (d), Callister & Rethwisch 9e. White iron < 1 wt% Si pearlite + ___________ very hard and ___________ ______________ iron heat treat white iron at 800-900°C graphite in ____________ reasonably strong and ductile Courtesy of Amcast Industrial Corporation Reprinted with permission of the Iron Castings Society, Des Plaines, IL

Types of Cast Iron (cont.) Compacted __________ iron relatively high _________________ good resistance to thermal shock lower oxidation at elevated temperatures Courtesy of Sinter-Cast, Ltd. Fig. 11.3(e), Callister & Rethwisch 9e.

Production of Cast Irons Fig.11.5, Callister & Rethwisch 9e. (Adapted from W. G. Moffatt, G. W. Pearsall, and J. Wulff, The Structure and Properties of Materials, Vol. I, Structure, p. 195. Copyright © 1964 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)

Limitations of Ferrous Alloys Relatively high densities Relatively low electrical conductivities Generally poor corrosion resistance

Nonferrous Alloys NonFerrous Alloys • Cu Alloys • Al Alloys Brass: Zn is subst. impurity (costume jewelry, coins, corrosion resistant) Bronze : Sn, Al, Si, Ni are subst. impurities (bushings, landing gear) Cu-Be : precip. hardened for strength • Al Alloys -low ρ: 2.7 g/cm3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct. aircraft parts & packaging) NonFerrous Alloys • Mg Alloys -very low ρ: 1.7 g/cm3 -ignites easily - aircraft, missiles • Ti Alloys -relatively low ρ: 4.5 g/cm3 vs 7.9 for steel -reactive at high T’s - space applic. • Refractory metals -high melting T’s -Nb, Mo, W, Ta • Noble metals -Ag, Au, Pt - oxid./corr. resistant Based on discussion and data provided in Section 11.3, Callister & Rethwisch 9e.

Metal Fabrication How do we fabricate metals? _____________________ ____________ - hammer (forged) Cast molten metal into mold _____________________ Rough stock formed to final shape Hot working vs. Cold working • Deformation ___________ high enough for ________________ • Large ______________ • Deformation below _________________ temperature • Strain hardening occurs • Small ______________

Metal Fabrication Methods (i) FORMING CASTING MISCELLANEOUS A o d force die blank • Forging (__________________) (wrenches, crankshafts) often at elev. T Adapted from Fig. 11.9, Callister & Rethwisch 9e. roll A o d • Rolling (________________) (I-beams, rails, sheet & plate) tensile force A o d die • Drawing (rods, wire, tubing) die must be well lubricated & clean ram billet container force die holder die A o d extrusion • __________ (rods, tubing) ductile metals, e.g. Cu, Al (hot)

Metal Fabrication Methods (ii) FORMING CASTING MISCELLANEOUS Casting- mold is filled with molten metal _________________________, perhaps alloying elements added, then _______ in a mold ______________________________ gives good production of shapes weaker products, internal defects

Metal Fabrication Methods (iii) FORMING CASTING MISCELLANEOUS • ________ Casting (large parts, e.g., auto engine blocks) What material will withstand T >1600°C and is ____________ and easy to mold? Answer: ______!!! To create mold, pack _____ around form (pattern) of desired shape Sand molten metal

Metal Fabrication Methods (iv) FORMING CASTING MISCELLANEOUS • _____________________ (low volume, complex shapes e.g., jewelry, turbine blades) Stage I — _____ formed by pouring ____________ around wax pattern. Plaster allowed to harden. wax I • Stage II — Wax is melted and then poured from mold—hollow mold cavity remains. II • Stage III — __________________ into mold and allowed to solidify. III

Metal Fabrication Methods (v) FORMING CASTING MISCELLANEOUS • Die Casting -- high ____________ -- for alloys having ____ melting temperatures • Continuous Casting -- __________ shapes (e.g., rectangular slabs, cylinders) molten solidified

Metal Fabrication Methods (vi) FORMING CASTING MISCELLANEOUS • _________________ (metals w/low ductilities) • ____________ (when fabrication of one large part is impractical) • Heat-affected ______: (region in which the microstructure has been changed). Fig. 11.10, Callister & Rethwisch 9e. [From Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), Iron Castings Society, Des Plaines, IL,1981.] piece 1 piece 2 fused base metal filler metal (melted) base metal (melted) unaffected heat-affected zone pressure heat point contact at low T densification by diffusion at higher T area contact densify

Thermal Processing of Metals Annealing: Heat to Tanneal, then cool slowly. Types of Annealing • Stress Relief: Reduce stresses resulting from: - plastic deformation - ___________ cooling - phase transform. • __________ (steels): Make very soft steels for good machining. Heat just below Teutectoid & hold for 15-25 h. • Full Anneal (steels): Make soft steels for good forming. Heat to get γ , then furnace-cool to obtain coarse pearlite. • _______________: Negate effects of cold working by (recovery/ recrystallization) • _________ (steels): Deform steel with large grains. Then heat treat to allow _______________ and formation of smaller grains. Based on discussion in Section 11.7, Callister & Rethwisch 9e.

Heat Treatment Temperature-Time Paths b) _____________ A _____________ P Tempering (Tempered Martensite) B A 100% 50% 0% c) Fig. 10.25, Callister & Rethwisch 9e. [Adapted from H. Boyer (Editor), Atlas of Isothermal Transformation and Cooling Transformation Diagrams, 1977. Reproduced by permission of ASM International, Materials Park, OH.]

Hardenability -- Steels • __________ – measure of the ability to form martensite • Jominy end quench test used to measure ___________. 24°C water specimen (heated to γ phase field) flat ground Rockwell C hardness tests Fig. 11.12, Callister & Rethwisch 9e. (Adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.) • Plot __________ versus distance from the quenched end. Hardness, HRC Distance from quenched end Fig. 11.13, Callister & Rethwisch 9e.

Reason Why Hardness Changes with Distance • The cooling rate _________ with distance from quenched end. 60 Martensite Martensite + Pearlite Fine Pearlite Pearlite Hardness, HRC 40 20 distance from quenched end (in) 1 2 3 600 400 200 A ® M P 0.1 1 10 100 1000 T(°C) M(start) Time (s) 0% 100% M(finish) Fig. 11.14, Callister & Rethwisch 9e. [Adapted from H. Boyer (Ed.), Atlas of Isothermal Transformation and Cooling Transformation Diagrams, 1977. Reproduced by permission of ASM International, Materials Park, OH.]

Hardenability vs Alloy Composition Cooling rate (°C/s) Hardness, HRC 20 40 60 10 30 50 Distance from quenched end (mm) 2 100 3 4140 8640 5140 1040 80 %M 4340 • ____________ curves for five alloys each with, C = _____________ Fig. 11.15, Callister & Rethwisch 9e. (Adapted from figure furnished courtesy Republic Steel Corporation.) • "Alloy Steels" (4140, 4340, 5140, 8640) -- contain Ni, Cr, Mo (0.2 to 2 wt%) -- these ___________ shift the "nose" to longer times (from A to B) -- martensite is easier to form T(°C) 10 -1 3 5 200 400 600 800 Time (s) M(start) M(90%) B A TE

Influences of Quenching Medium & Specimen Geometry • Effect of quenching medium: Medium air oil water Severity of Quench _________ Hardness _________ • Effect of specimen geometry: When surface area-to-volume ratio increases: -- cooling rate throughout interior increases -- hardness throughout interior increases Position center surface Cooling rate low high Hardness

Precipitation Hardening • Particles impede _________ motion. • Ex: Al-Cu system • Procedure: 10 20 30 40 50 wt% Cu L  + L α α + θ θ θ + L 300 400 500 600 700 (Al) T(ºC) composition range available for precipitation hardening CuAl2 A -- Pt A: _______________ (get α solid solution) B Pt B -- Pt B: ______ to room temp. (retain α solid solution) C -- Pt C: ________ to nucleate small θ __________ within α phase. Other alloys that precipitation harden: • Cu-Be • Cu-Sn • Mg-Al Fig. 11.25, Callister & Rethwisch 9e. (Adapted from J.L. Murray, International Metals Review 30, p.5, 1985. Reprinted by permission of ASM International.) Temp. Time Pt A (sol’n heat treat) Pt C (precipitate ) Adapted from Fig. 11.23, Callister & Rethwisch 9e.

Influence of Precipitation Heat Treatment on TS, %EL • 2014 Al Alloy: • _________ on TS curves. • __________ T accelerates process. • ________ on %EL curves. %EL (2 in sample) 10 20 30 1min 1h 1day 1mo 1yr 204ºC 149ºC precipitation heat treat time precipitation heat treat time tensile strength (MPa) 200 300 400 100 1min 1h 1day 1mo 1yr 204ºC non-equil. solid solution many small precipitates “aged” fewer large “overaged” 149ºC Fig. 11.28, Callister & Rethwisch 9e. [Adapted from Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th ed., H. Baker (Managing Ed.), 1979. Reproduced by permission of ASM International, Materials Park, OH.]

Summary • Ferrous alloys: steels and cast irons • Non-ferrous alloys: -- Cu, Al, Ti, and Mg alloys; refractory alloys; and noble metals. • Metal fabrication techniques: -- forming, casting, miscellaneous. • Hardenability of metals -- measure of ability of a steel to be heat treated. -- increases with alloy content. • Precipitation hardening --hardening, strengthening due to formation of precipitate particles. --Al, Mg alloys precipitation hardenable.