Metal – Designation & Properties R. Lindeke Engr. 2110 Introduction to Materials for Engineers

Taxonomy of Metals Steels Cast Irons <1.4 wt% C 3-4.5 wt% C Alloys Steels Ferrous Nonferrous Cast Irons Cu Al Mg Ti <1.4wt%C 3-4.5 wt%C Adapted from Fig. 11.1, Callister 7e. Steels <1.4 wt% C Cast Irons 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 g austenite +L +Fe3C a ferrite + L+Fe3C d (Fe) Co , wt% C Eutectic: Eutectoid: 0.76 4.30 727°C 1148°C T(°C) 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.)

Alloy Taxonomy – (FerrousFocus!)

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 austenitic 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 Hardenability + ++ +++ TS - + ++ 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 V. corros. resistant Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 7e.

LOW-CARBON STEEL ~<0.25%C High Strength Low Alloy Steel 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 engineers AISI- American Iron and Steel Institute ASTM- American Society for Testing and Materials UNS- 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 ductile Always used in hardened/tempered condition – wear and indentation resistant Tool/die steels contain high Carbon and Chromium, Vanadium, tungsten and molybdenum  Carbides

Stainless Steel 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

CAST IRONS – Carbon > 2.14 wt. %C , usually 3-4.5wt%C Complete Melting 1150 oC-1300 oC Silicon > 1%, slower cooling rates during solidification Gray, White, Nodular, malleable

Types of Cast Iron Gray iron Ductile 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 Iron White 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.

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. impurity (bushings, landing gear) Cu-Be : precip. hardened for strength • Al Alloys -lower r : 2.7g/cm3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct. aircraft parts & packaging) NonFerrous Alloys • Mg Alloys -very low r : 1.7g/cm3 -ignites easily - aircraft, missiles • Ti Alloys -lower r : 4.5g/cm3 vs 7.9 for steel -reactive at high T - space applic. • Refractory metals -high melting T -Nb, Mo, W, Ta • Noble metals -Ag, Au, Pt - oxid./corr. resistant Based on discussion and data provided in Section 11.3, Callister 7e.

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? Forming Operations 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

Metal Fabrication Methods - I FORMING CASTING JOINING A o d force die blank • Forging (Hammering; Stamping) (wrenches, crankshafts) often at elev. T Adapted from Fig. 11.8, Callister 7e. roll A o d • Rolling (Hot or Cold 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 • Extrusion (rods, tubing) ductile metals, e.g. Cu, Al (hot)

Metal Fabrication Methods - II FORMING CASTING JOINING 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

Metal Fabrication Methods - II FORMING CASTING JOINING • Sand Casting (large parts, e.g., auto engine blocks) • Die Casting (high volume, low T alloys) Sand molten metal • Continuous Casting (simple slab shapes) molten solidified • Investment Casting (low volume, complex shapes e.g., jewelry, turbine blades) plaster die formed around wax prototype wax

Metal Fabrication Methods - III FORMING CASTING JOINING • Powder Metallurgy (materials w/low ductility) • 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) 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 stress caused by: -plastic deformation -nonuniform cooling -phase transform. • Spheroidize (steels): Make very soft steels for good machining. Heat just below TE & hold for 15-25 h. • Full Anneal (steels): Make soft steels for good forming by heating to get g , then cool in furnace to get coarse P. • Process Anneal: Negate effect of cold working by (recovery/ recrystallization) • Normalize (steels): Deform steel with large grains, then normalize to make grains small. Based on discussion in Section 11.7, Callister 7e.

Heat Treatments Annealing Quenching Tempered Martensite a) b) c) TE 800 Austenite (stable) a) b) TE T(°C) A Annealing P 600 Quenching Tempered Martensite B 400 A 100% Adapted from Fig. 10.22, Callister 7e. 50% 0% c) 0% 200 M + A 50% M + A 90% -1 3 5 10 10 10 10 time (s)

Hardenability--Steels • Ability to form martensite • Jominy end quench test to measure hardenability. 24°C water specimen (heated to g phase field) flat ground Rockwell C hardness tests 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.) • Hardness versus distance from the quenched end. Hardness, HRC Distance from quenched end Adapted from Fig. 11.12, Callister 7e.

Why Hardness Changes W/Position • The cooling rate varies with position. 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) 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.)

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 • Jominy end quench results, C = 0.4 wt% C Adapted from Fig. 11.14, Callister 7e. (Fig. 11.14 adapted from figure furnished courtesy Republic Steel Corporation.) • "Alloy Steels" (4140, 4340, 5140, 8640) --contain Ni, Cr, Mo (0.2 to 2wt%) --these elements shift the "nose". --martensite is easier to form. T(°C) 10 -1 3 5 200 400 600 800 Time (s) M(start) M(90%) shift from A to B due to alloying B A TE

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

Precipitation Hardening • Particles impede dislocations. • Ex: Al-Cu system • Procedure: 10 20 30 40 50 wt% Cu L +L a a+q q +L 300 400 500 600 700 (Al) T(°C) composition range needed for precipitation hardening CuAl2 A --Pt A: solution heat treat (get a solid solution) B Pt B --Pt B: quench to room temp. C --Pt C: reheat to nucleate small q crystals within a crystals. Other precipitation systems: • Cu-Be • Cu-Sn • Mg-Al Adapted from Fig. 11.24, Callister 7e. (Fig. 11.24 adapted from J.L. Murray, International Metals Review 30, p.5, 1985.) Temp. Time Pt A (sol’n heat treat) Consider: 17-4 PH St. Steel and Ni-Superalloys too! Pt C (precipitate ) Adapted from Fig. 11.22, Callister 7e.

Effect of time at Temperature during Precipitation Hardening