Nonferrous
Metals
and
Alloys:
R
1
"1O
Q-C
o
22
O
P
CW
(D
5
(D
"1&
PTEA
CHProperties, and
Applications
° Nonferrousmetals include awidevarietyofmaterials, ranging from aluminum
to zinc, with special properties that are indispensable in many consumer and
commercial products.
° This chapter introduces each class of nonferrous metal and its alloys, and
briefly describestheir methods ofproduction.
¢ Their physical and mechanical properties are then summarized, along with
general guidelines for their selection and applications, together with several
examples
° Shape-memory alloys, amorphous alloys, and metal foams are also described,
withexamples oftheir unique applications.
6.|
Introduction
Nonferrous metals and alloys cover a wide range, from the more common metals
(such as aluminum, copper, and magnesium) to high-strength, high-temperature
alloys (such as those of tungsten, tantalum, and molybdenum). Although generally
more expensive than ferrous metals (Table 6.1), nonferrous metals and alloys have
numerous important applications because ofpropertiessuch as goodcorrosion
resist-ance, high thermal and electrical conductivity, low density, and ease of fabrication
(Table 6.2). Typical examples of nonferrous metal and alloy applications are
alu-minum for cooking utensils and aircraft bodies, copper wire for electrical power cords, zinc for galvanized sheet metal forcar bodies, titanium for jet-engine turbine blades and for orthopedicimplants, and tantalum for rocket engines.
As an example, a turbofanjet engine forthe Boeing 757 aircrafttypically con-tains the followingnonferrous metals and alloys: 38% Ti, 37% Ni, 12% Cr, 6% Co,
5% Al, 1% Nb, and0.02% Ta. Withoutthese materials,a jet engine (Fig. 6.1) could not be designed, manufactured, and operated at the power and efficiency levels
required.
This chapter introduces the general properties, the production methods, and
the important engineeringapplications fornonferrous metals andalloys. The
manu-facturing properties of thesematerials (such as formability,machinability, and weld-ability) are described invarious chapters throughout this text.
6.I 6.2 6.3 6.4 6.5 6.6 6.1 6.8 6.9 6.l0 6.|| 6.12 6.l3 6.I4 Introduction |5|
Aluminumand Aluminum
Alloys |52
Magnesiumand
MagnesiumAlloys |57
Copper and Copper
Alloys |58
Nickeland Nickel
Alloys |60
Superalloys |6|
TitaniumandTitanium
Alloys |62
Refractory Metalsand
Alloys |63 Beryllium |64 Zirconium |64 Low-me|tingA|loys |64 Precious Metals |66 Shape-memoryAlloys (Smart Materials) |66 AmorphousAlloys (MetallicGlasses) |67
6.I5 Metal Foams |67
EXAMPLE:
6.| AnAll-aluminum Automobile |56
Chapter 6 Nonferrous Metals and Alloys: Production,General Properties,andApplications
TABLE 6.I
Approximate Cost-per-unit-volume forWroughtMetals and Plastics Relative to theCostofCarbonSteel
Gold 30,000 Magnesium alloys 4-6
Silver 600 Aluminumalloys 2-3
Molybdenumalloys 75-100 High-strengthlow-alloy steels 1.4
Nickel 20 Gray cast iron 1.2
Titaniumalloys 20-40 Carbon steel 1
Copperalloys 8-10 Nylons, acetals, and silicon rubber” 1.1-2
Zinc alloys 1.5-3.5 Otherplastics and elastomers* 0.2-1
Stainlesssteels 2-9
*Asmolding compounds.
Note: Costsvarysignificantly with quantityof purchase,supply and demand,sizeand shape, and other factors.
TABLE 6.2
GeneralCharacteristicsofNonferrous Metals andAlloys
Material Characteristics Nonferrous alloys Aluminum Magnesium Copper Superalloys Titanium Refractorymetals Preciousmetals
Moreexpensive than steels and plastics;Wide range ofmechanical,
physical, and electricalproperties; good corrosion resistance;
high-temperature applications
Alloyshave high strength-to-weight ratio; highthermal and electrical conductivity; good corrosion resistance; good
manufacturing properties
Lightestmetal; good strength-to-Weight ratio
High electrical and thermalconductivity; good corrosion
resistance;good manufacturing properties
Good strengthand resistance tocorrosion at elevated temperatures
can be iron-,cobalt-, and nickel-based alloys
Higheststrength-to-Weight ratio of all metals; good strength and
corrosion resistance at hightemperatures
Molybdenum, niobium (columbium), tungsten, and tantalum; high
strength at elevated temperatures
Gold, silver,and platinum; generally good corrosion resistance
6.2
Aluminum and Aluminum
Alloys
The important advantages ofaluminum (Al) andits alloys are their high strength-to-weightratios, resistance to corrosion by many chemicals, high thermal and electrical conductivities, nontoxicity, reflectivity, appearance, and ease of formability and machinability; they are also nonmagnetic. The principal uses of aluminum and its
alloys,indecreasingorderofconsumption,areincontainers and packaging (aluminum
cans and foil), architectural and structural applications, transportation (aircraft and
aerospace applications, buses, automobiles, railroad cars, and marine craft), electrical applications (as economical and nonmagnetic electrical conductors), consumer durables (appliances, cooking utensils, andfurniture), and portable tools (Tables 6.3
and6.4).Nearlyallhigh-voltagetransmissionWiringismadeofaluminum.In its
struc-tural (load-bearing) components, 82% ofaBoeing 747 aircraft and 70% of aBoeing 777 aircraft is aluminum. The frame and the body panels of the new Rolls Royce
Section 6.2 Aluminum and Aluminum Alloys
Low-pressurecompressor High-pressure
Fan T' alloy Ti orAI alloy turbine LOW_preSSure
N' all0Y turbine N' II Hig|q_p|'9SSU|re COlT1lf)US1lOl1 3 Oy compressor Chamber Inletcase AI alloy Ti or Ni alloy Ni all0Y Turbine Turbine
blades exhaust case
Ni alloy Ni alloy Accessory section
Al alloy or Fealloy
FIGURE 6.I Cross section of a jet engine (PW/2037), showing various components and the alloys used inmanufacturing them. Source: Courtesyof UnitedAircraft Pratt SC Whitney.
TABLE 6.3
Properties ofSelected AluminumAlloys atRoomTemperature
Elongation
Ultimatetensile Yield strength in 50mm
Alloy (UNS) Temper strength (MPa) (MPa) (%)
1100 (A91100) O 90 35 35-45 1100 H14 125 120 9-20 2024 (A92024) O 190 75 20-22 2024 T4 470 325 19-20 3003 (A93003) O 110 40 30-40 3003 H14 150 145 8-16 5052 (A95052) O 190 90 25-30 5052 H34 260 215 10-14 6061 (A96061) O 125 55 25-30 6061 T6 310 275 12-17 7075 (A97075) O 230 105 16-17 7075 T6 570 500 11
Phantom coupe are made of aluminum, improving the car’s strength-to-Weight and
torsional rigidity-to-Weight ratios.
Aluminum alloys are available as mill
products-that
is, as Wrought productsmade into various shapes by rolling, extrusion, drawing, and forging (Chapters 13
through 15). Aluminum ingots are available for casting, as is aluminum in powder
form for powder-metallurgy applications (Chapter 17). Most aluminum alloys can
|54 Chapter 6 Nonferrous Metalsand Alloys: Production, General Properties,and Applications
TABLE 6.4
Manufacturing Characteristics andTypical ApplicationsofSelectedWroughtAluminum Alloys Characteristics*
Corrosion
Alloy resistance Machinability Weldability Typicalapplications
1100 A -D A Sheet-metalwork, spunhollowware, tinstock
2024 C -C B-C Truck wheels, screwmachine products, aircraft structures
3003 A -D A Cooking utensils, chemicalequipment, pressure vessels,
sheet-metalwork, builders’ hardware, storage tanks
5052 A -D A Sheet-metalwork, hydraulic tubes, and appliances; bus,
truck,and marineuses
6061 B -D A Heavy-duty structures where corrosion resistance isneeded;
truck and marine structures, railroad cars,furniture, pipelines, bridgerailings, hydraulic tubing
7075 C B-D D Aircraft and other structures, keys, hydraulic fittings
’*A,excellent;D, poor.
There are two types ofwrought alloys of aluminum:
I. Alloys that can be hardened bycold working andare not heat treatable.
2. Alloys that can be hardened byheat treatment.
DesignationofWroughtAluminum Alloys. Wrought aluminum alloys are
identi-fied by four digits and by a temper designation that shows the condition of the
material. (Seealso UnifiedNumberingSystem later inthis section.)Themajor alloy-ing elementis identified by the first digit:
1xxx-Commercially pure aluminum: excellent corrosion resistance, high
electrical and thermal conductivity, good workability, low strength, not
heat treatable
2xxx-Copper:
high strength-to-weight ratio, low resistance to corrosion,heat treatable
3xxx-Manganese:
good workability, moderate strength, generally not heattreatable
4xxx-Silicon:
lower melting point, forms an oxide film of a dark gray to charcoal color,generally not heat treatable5xxx-Magnesium:
good corrosion resistance and weldability, moderate to high strength, not heat treatable6xxx-Magnesium
and silicon: medium strength; good formability,machin-ability, weldability, and corrosion resistance; heat treatable
7xxx-Zinc:
moderate toVery highstrength, heat treatable8xxx-Other
elementThe second digit inthese designations indicates modificationsofthe alloy. For
the 1xxx series, the third and fourth digits stand for the minimumamount of
alu-minum inthe alloy. Forexample, 1050 indicatesaminimumof99.50%Al, and 1090
indicates aminimum of99.90% Al.In otherseries, the third andfourthdigitsidentify the different alloys inthe group and have no numerical significance. For instance, a
typical aluminum beverage can may consistof the following aluminum alloys, all in
the H19 condition (which isthe highestcold-worked state): 3004 or3104 forthe can
body, 5182 for the lid, and 5042 forthe tab. These alloysare selected for their
Section 6.2 Aluminum and AluminumAlloys
Designation of Cast Aluminum Alloys. Designations for cast aluminum alloys
also consistof four digits. The first digit indicatesthe major alloygroup, as follows:
1xx.x-Aluminum
(99.00% minimum)2xx.x-Aluminum-copper
3xx.x-Aluminum-silicon
(with copperand/or magnesium)4xx.x-Aluminum-silicon
5xx.x-Aluminum-magnesium
6xx.x-Unused
series7xx.x-Aluminum-zinc
8xx.x-Aluminum-tin
In the 1xx.x series, the secondand thirddigits indicate the minimum aluminum
content, as do the third and fourth in wrought aluminum. For the other series, the
second and third digits haveno numerical significance. The fourthdigit (to the right
of the decimal point) indicates the productform.
Temper Designations. The temper designations for both wrought and cast
alu-minum are asfollows:
°
F-As
fabricated (by cold or hotworking or by casting)°
O-Annealed
(fromthe cold-worked or the cast state)°
H-Strain
hardened bycold working (for wrought products only) °T-Heat
treated°
W-Solution
treatedonly (unstable temper)UnifiedNumbering System. Asis the casewith steels, aluminum andother
nonfer-rous metals and alloys now are identified internationally bythe Unified Numbering
System (UNS), consisting of aletter indicating the generalclass ofthe alloy, followed
by five digits indicating itschemicalcomposition. For example,A is foraluminum, C
forcopper, N fornickel alloys, P for precious metals, andZ for zinc. In the UNS
des-ignation, 2024 wrought aluminum alloy is A92024.
Production. Aluminum wasfirstproducedin 1825. Itisthe mostabundantmetallic
element, makingup about 8% ofthe earth’scrust, and isproduced in aquantity sec-ond only to that of iron. The principal ore for aluminum is bauxite, which is a
hydrous (water-containing) aluminum oxide and includes variousotheroxides.After theclay and dirt are washed off, the ore is crushed intopowder andtreated with hot
caustic soda (sodium hydroxide) to remove impurities. Next, Alumina (aluminum
oxide) is extractedfrom this solution and then dissolvedin amolten sodium-fluoride
and aluminum-fluoride bath at 940° to 980°C. Thismixture is then subjected to
di-rect-currentelectrolysis.Aluminum metal forms atthe cathode (negative pole), while
oxygenis releasedatthe anode(positive pole). Commerciallypurealuminumis upto
99.99% Al, also referred toin industryas “four nines” aluminum. Theproduction
process consumesagreat dealofelectricity, whichcontributes significantly tothecost
ofaluminum.
Porous Aluminum. Blocks of aluminum have beenproduced that are 37% lighter
than solid aluminum and have uniform permeability (microporosity). This
charac-teristic allows their use in applications where a vacuum or differential pressure has
to be maintained. Examples are the vacuum holding of fixtures for assembly and
automation, and the vacuum forming or thermoforming of plastics (Section 196).
These blocks are 70to 90% aluminum powder;the rest is epoxy resin. They can be
|56 Chapter 6 Nonferrous Metalsand Alloys: Production, GeneralProperties, and Applications
EXAMPLE
6.|
An All-aluminumAutomobileAluminum usein automobiles and in lighttrucks has
been increasing steadily. As recently as 1990, there were no aluminum-structured passenger cars in pro-duction anywhere in the world, but in 1997 there
were seven, including the Plymouth Prowler and the
AudiA8 (Fig. 6.2). With weightsavings of upto47%
over steel vehicles, such cars use less fuel, create less
pollution, and are recyclable.
New alloys and new design and manufacturing
methodologies had to be developed. For example, welding and adhesive bonding procedures had to be
refined, the structural frame design had to be
optimized, and new tooling designs (toallow forming
of aluminum) had to be developed. Because of these
new technologies, the desired environmental savings
were able to be realized without an accompanying
drop in performance or safety. In fact, the Audi A8 is
the first luxury-class car to earn a dual five-star
(highest safety) rating for both driver and front-seat
passenger in the National Highway Transportation
Safety Administration (NHSTA) New CarAssessment
Program.
ia)
Fioboticallyapplied, advanced arc-weldingprocesses
provideconsistenthigh-qualityassemblyofcastings,
extrusions,and sheetcomponents
Die-castnodes arethin walled
tomaximizeweight reduction,
yetprovide high performance
,ya ., ..§££“
3
",; _, .a _ to 5`
‘Z ‘ffm .~¢¢¢~ 1: fmt. E. f .sy `! ~ ~&Z§;i,;: ‘ rrcc _pgl/,
gg . .,,,,-
pggg 6, Q V. ,, _,Z 7/fi:»'
__ W/
ee.. Qatar” ccrrre~liia `i‘i llii
ii .. t ,
;:£f¥§;fr¢~,
i/z;ri,. ix:
"1=~>;r:...,u lliliifiiisg. in
""*=~-‘»» reeppp, Strong,thin-walled extrusions
fi exhibit highductiiity, energy
i..,ai absorption, andtoughness
Advanced extrusion bendingprocesses
supportcomplex shapesand tight radii
(bi
FIGURE 6.2 ia) The Audi A8 automobile, whichhas an all-aluminum body structure. (b) The aluminum body structure,
Section 6.3 Magnesium
6.3
Magnesium and Magnesium
Alloys
Magnesium (Mg) isthe lightest engineeringmetal available, andithas good vibration-damping characteristics. Its alloys are used in structural and nonstructural applica-tions wherever weight is of primary importance. Magnesium is also an alloying element invarious nonferrous metals.
Typical uses of magnesium alloys are in aircraft and missile components,
material-handling equipment, portablepower tools, ladders, luggage, bicycles,
sport-ing goods, and general lightweightcomponents. Like aluminum, magnesium is find-ingincreased use inthe automotive sector,mainly in order to achieveweight savings.
Magnesium alloys are available either as castings(such as die-cast cameraframes) or
as wroughtproducts (such as extruded bars and shapes, forgings, and rolledplates
and sheets). Magnesium alloys are also used in printing and textile machinery to
minimize inertial forces inhigh-speed components(Section 3.2).
Becauseitis not sufficiently stronginits pure form, magnesium is alloyed with
various elements (Table 6.5) inorder to gain certainspecific properties, particularly
a high strength-to-weight ratio. A variety of magnesium alloys have good casting,
forming, and machining characteristics. Because they oxidize rapidly (i.e., they are
pyrop/ooric), a fire hazard exists, and precautions must be taken when machining, grinding, or sand-casting magnesium alloys. Products made of magnesium and its
alloys are, nonetheless, not a fire hazard during normal use.
Designation of Magnesium Alloys. Magnesium alloys are designated with the
following:
a. One or two prefix letters, indicatingthe principal alloyingelements.
b. Two or three numerals, indicatingthe percentage ofthe principal alloying
ele-ments and rounded off to the nearest decimal.
c. A letter ofthe alphabet (except the letters I andO) indicatingthe standardized
alloywith minor variationsin composition.
d. A symbol for the temper of the material, following the system used for
alu-minum alloys.
For example, consider the alloy AZ91C-T6:
° The principal alloying elements are aluminum (A, at 9%, rounded off) and
zinc (Z, at 1%).
° The letter C, the third letter of the alphabet, indicates that this alloy was the
third one standardized (later than A and B, which were the first and second
and MagnesiumAlloys l57
TABLE 6.5
Properties andTypical FormsofSelected WroughtMagnesiumAlloys Ultimate
0 tensile Yield Elongation
COIHPOSIIIOH( M strength strength in 50 mm
Alloy Zn Mn Zr Th Condition (MPa) (MPa) (%) Typical forms
AZ31B 3.0 1.0 0.2
_
-
F 200 ExtrusionsH24 220 Sheet and plates
AZSOA 8.5 0.5 0.2
- -
T5 275 Extrusions and forgingsHK31A
-
-
0.7 3 H24 200 Sheet and platesChapter 6 Nonferrous Metalsand Alloys: Production, GeneralProperties, and Applications
alloys that were standardized respectively). Specific information related to this
standardized alloycanthen beobtained.
° T6 indicates thatthis alloy has been solutiontreated andartificially aged.
Production. Magnesium is the third-most-abundant metallic element (2%) in the
earth’scrust, afteriron and aluminum. Mostmagnesiumcomes from seawater, which
contains 0.13% magnesium in the form of magnesium chloride. First produced in
1808, magnesium metal can be obtained electrolytically or by thermal reduction.In the electrolytic inet/ood, seawater is mixed with lime (calcium hydroxide) insettling tanks. Magnesium hydroxide precipitates to the bottom, is filtered and mixed with
hydrochloric acid. The resulting solution is subjected to electrolysis (asis done with
aluminum), producing magnesium metal, which is then cast into ingots for further
processing into various shapes. In the thermal-reduction met/ood, magnesium ores
(dolomite, magnesite, and other rocks) are broken down with reducing agents (such
as powdered ferrosilicon, an alloy of iron and silicon) by heating the mixture in a
vacuum chamber. As a result of this reaction, vapors of magnesium form, and they
condense into magnesium crystals, which are then melted, refined, and poured into ingotsto beprocessed furtherinto various shapes.
6.4
Copper and Copper
Alloys
Firstproduced inabout 4000B.C., copper (Cu,from the Latin cuprurn) andits alloys
have properties somewhat similar to thoseof aluminum and its alloys. In addition,
they areamong the best conductors of electricity and heat (Tables 3.1 and 3.2), and
theyhavegood corrosion resistance. Copper andits alloys can beprocessed easilyby
various forming, machining, casting, and joining techniques.
Copper alloys often are attractive forapplications in which a combination of
electrical, mechanical, nonmagnetic, corrosion-resistant, thermally conductive, and wear-resistant qualities are required. Applications include electrical and electronic components, springs, coins, plumbing components, heat exchangers, marine hard-ware, and consumer goods (such as cooking utensils, jewelry, and other decorative objects). Although aluminum is the most common material for dies in polymer injection molding (Section 19.3), copperoften is used because of its better thermal properties. Pure copper also can be used as a solid lubricant in hot-metal-forming
operations.
Copperalloys can acquire awide varietyof properties bythe additionof alloy-ing elements and byheat treatment, to improve their manufacturing characteristics.
The most common copper alloys are brasses and bronzes. Brass (an alloy ofcopper
and zinc) is one of the earliest alloys developed and has numerous applications,
in-cluding decorative objects(Table6.6). Bronzeis an alloy ofcopper andtin(Table6.7).
There are also other bronzes, such as aluminum bronze (an alloy of copper and
aluminum) and tin bronzes. Beryllium copper (orberyllium bronze) and phosphor
bronze havegoodstrength and hardness for applicationssuch asspringsand bearings. Other major copperalloys are copper nickelsand nickelsili/ers.
Designation ofCopper Alloys. Inthe Unified Numbering System, copperis
iden-tified with the letter C, such as C26200 for cartridge brass. In addition to being identified by their composition, copper and copper alloys are known by various names (Tables 6.6 and 6.7). The temper designations (such as 1/Z hard, extra
hard,extra spring, and so on) are basedon degree of cold work (suchas byrolling
Section 6.4 Copperand CopperAlloys |59
TABLE 6.6
Properties andTypical ApplicationsofSelectedWroughtCopperandBrasses Ultimate
Nominal tensile Yield Elongation
composition strength strength in 50 mm
Typeand UNSnumber (%) (MPa) (MPa) (%) Typicalapplications
Electrolytictough-pitch 99.90Cu, 220-450 70-365 55-4 Downspouts, gutters, roofing, gaskets,
copper (C11000) 0.04 O auto radiators, bus bars,nails, printing
rolls, rivets
Red brass, 85% 85.0 Cu, 270-725 70-435 55-3 Weather stripping,conduits, sockets,
(C23000) 15.0Zn fasteners,fire extinguishers, condenser
and heat-exchanger tubing
Cartridgebrass,70% 70.0 Cu, 300-900 75-450 66-3 Radiatorcores and tanks,flashlight
(C26000) 30.0 Zn shells, lamp fixtures, fasteners, locks,
hinges, ammunitioncomponents,
plumbing accessories
Free-cutting brass 61.5 Cu, 340-470 125-310 53-18 Gears,pinions, automatic high-speed
(C36000) 3.0 Pb, 35.5 Zn screwmachineparts
Navalbrass (C46400 60.0 Cu, 39.25Zn, 380-610 170-455 50-17 Aircraft:turnbuckle barrels, balls,
to C46700) 0.75 Sn bolts; marine hardware: propeller
shafts, rivets, valve stems,condenser plates
TABLE 6.7
Properties andTypicalApplicationsofSelectedWroughtBronzes
Ultimate
Nominal tensile Yield Elongation
Type and UNS composition strength strength in50mm
number (%) (MPa) (MPa) (%) Typicalapplications
Architectural bronze 57.0 Cu, 3.0 Pb, 415 140 30 Architectural extrusions, storefronts,
(C38500) 40.0Zn (asextruded) thresholds, trim,butts,hinges
Phosphor bronze, 95.0 Cu, 5.0 Sn, 325-960 130-550 64-2 Bellows, clutchdisks,cotterpins,
5% A(C51000) trace P diaphragms,fasteners, wire brushes,
chemical hardware, textilemachinery
Free-cuttingphosphor 88.0 Cu, 4.0 Pb, 300-520 130-435 50-15 Bearings, bushings,gears, pinions,
bronze (C54400) 4.0 Zn,4.0 Sn shafts,thrust washers, valveparts
Low-silicon bronze, 98.5 Cu, 1.5 Si 275-655 100-475 55-11 Hydraulic pressure lines, bolts, marine
B (C65100) hardware, electricalconduits,
heat-exchanger tubing
Nickel silver,65-10 65.0 Cu,25.0 Zn, 340-900 125-525 50-1 Rivets, screws,slide fasteners,
(C74500) 10.0 Ni hollowware, nameplates
Production. Copper isfound inseveraltypes of ores, themost common beingsulfide
ores. The ores are generally of low grade (althoughsomecontainup to 15% Cu) and
usuallyareobtained from open-pit mines.Theslurry isground intofineparticlesinball
mills(rotating cylinders withmetal balls insideto crushthe ore,as shown in Fig. 17.6b,
the resulting particles are then suspended inwater to form a slurry.Chemicals andoil
are then added,andthemixtureisagitated. The mineral particles formafroth, whichis
scrapedand dried. Thedry copperconcentrate (as much asone-third ofwhich is cop-per) is traditionally smelted (melted and fused) and refined; this process is known as
|60 Chapter 6 Nonferrous Metalsand Alloys: Production, General Properties,andApplications
electricalconductors,thecopperis refinedfurtherelectrolytically toapurityofat least
99.95% (oxygen-free electrolytic copper).Amore recent technique for processing cop-peris hydrometallurgy,a process involving both chemical and electrolytic reactions.
6.5
Nickel
and
Nickel Alloys
Nickel (Ni) is a silver-white metal discovered in 1751 and a major alloying element
that imparts strength, toughness, and corrosion resistance. It is used extensively in
stainless steels and innickel-based alloys (also called superalloys). Nickel alloys are used in high-temperature applications (such as jet engine components, rockets, and nuclear power plants), in food-handling and chemical-processing equipment, in
coins, and in marine applications. Because nickel is magnetic, nickel alloys also are
usedinelectromagnetic applications, such as solenoids.Theprincipaluse ofnickel as
ametalis inthe electroplating ofparts fortheir appearance and fortheimprovement
of their corrosion and Wear resistance. Nickel alloys have high strength and corro-sion resistance at elevated temperatures. Alloying elements innickel are chromium, cobalt, and molybdenum. The behavior of nickel alloys in machining, forming,
cast-ing, andWeldingcan be modified byvarious otheralloyingelements.
A varietyof nickel alloys, with awide range of strengthsat different tempera-tures have been developed (Table 6.8). Although trade names are still in wide use,
nickel alloysare now identifiedinthe UNSsystemwiththe letter N. Thus, Hastelloy
Gis novv N06007. Other common trade names are:
° Monelis anickel-copper alloy.
° Inconel is a nickel-chromium alloy with a tensile strength of upto 1400 MPa.
Hastelloy (also anickel-chromiumalloy) has goodcorrosion resistance and high strength atelevated temperatures.
° Nichrome (an alloy of nickel, chromium, and iron) has highelectrical resistance and ahigh resistance to oxidation and is used for electrical heatingelements. ° Invarand Kovar (alloys of iron and nickel) have relatively low sensitivity to
tem-perature (Section 3.6).
TABLE 6.8
Properties andTypicalApplicationsofSelected Nickel Ailoys (All AreTrade Names)
Ultimate
Nominal tensile Yield Elongation
Type and UNS composition strength strength in 50 mm
number (%) (MPa) (MPa) (%) Typicalapplications
Nickel 200 (annealed) None 380-550 100-275 60-40 Chemical and food processing
industry, aerospace equipment,
electronicparts
Duranickel301 4.4 Al, 0.6 Ti 1300 900 28 Springs, plastics extrusion equipment,
(age hardened) moldsforglass, diaphragms
Monel R-405 30Cu 525 230 35 Screw-machine products, water meter
(hotrolled) parts
Monel K-500 29Cu, 3Al 1050 750 30 Pump shafts, valve stems, springs
(age hardened)
Inconel 600 15 Cr, 8Fe 640 210 48 Gasturbine parts,heat-treating
(annealed) equipment, electronic parts, nuclear
reactors
Hastelloy C-4 16 Cr, 15 Mo 785 400 54 Parts requiringhigh-temperature
(solution treated stability and resistance to
Section 6.6 Superalloys
Production. The main sources of nickel are sulfide and oxide ores, all of which
havelow concentrationsof nickel.Nickel metalis produced bypreliminary
sedimen-tary and thermal processes, followed by electrolysis; this sequence yields 99.95%
pure nickel. Although nickel also is present in the ocean bed in significantamounts,
undersea miningis notyet economical.
6.6
Superalloys
Superalloys are important in high-temperature applications; hence, they are also
known as heat-resistant orhigh-temperature alloys. Superalloys generally have good
resistance to corrosion, mechanical and thermal fatigue, mechanical and thermal shock, creep, and erosion, at elevated temperatures. Major applications of
superal-loys are in jet engines and gas turbines. Other applications are in reciprocating
engines, rocket engines, tools and dies for hot working of metals, and the nuclear,
chemical, and petrochemical industries. Generally, superalloys are identified by
trade names or by special numbering systems, and they are available in avariety of
shapes. Most superalloys have amaximum service temperatureof about 1000°Cin
structural applications. The temperatures can be as high as 1200°C for
non-load-bearing components.
Superalloys are referred to as iron-based, cobalt-based,or nic/eel-based. ° Iron-based superalloys generally contain from 32 to 67% Fe, from 15to22%
Cr, and from9 to 38% Ni. Common alloys inthis group are the Incoloyseries. ° Cobalt-based superalloys generally contain from 35 to 65% Co, from 19 to
30% Cr, andup to 35% Ni. These superalloys are notas strong as nickel-based
superalloys, butthey retain their strength at highertemperatures.
° Nickel-based superalloys are themost common ofthe superalloys and are avail-able in a wide variety of compositions (Table 6.9). The proportion of nickel is
from 38 to 76%. These superalloys also contain up to 27% Cr and 20% Co.
Common alloysin thisgroupare theHastelloy Inconel, Nimonic, René, Udimet,
Astroloy and Waspaloy series.
TABLE 6.9
Properties andTypicalApplicationsofSelected Nickel-based Superalloys at8T0°C
(All Are Trade Names)
Elongation
Ultimate tensile Yield strength in 50 mm
Alloy Condition strength (MPa) (MPa) Typicalapplications
Astroloy Wrought 770 690 Forgings forhigh-temperature use
HastelloyX Wrought 255 180 ]etengine sheet parts
IN-100 Cast 885 695 _letengine blades and Wheels
IN-102 Wrought 215 200 Superheaterand jet engineparts
Inconel 625 Wrought 285 275 Aircraftengines andstructures, chemical
processingequipment
Inconel 718 Wrought 340 330 jetengine and rocketparts
MAR-M 200 Cast 840 760 ]etengine blades
MAR-M 432 Cast 730 605 Integrally cast turbine wheels
René41 Wrought 620 550 Jet engineparts
Udimet 700 Wrought 690 635 _jet engineparts
|62 Chapter6 Nonferrous Metalsand Alloys: Production,General Properties, and Applications
6.7
Titanium
and
Titanium
Alloys
Titanium(Ti, namedafter the Greek god Titan) is a silverywhite metal discovered in
1791, but not produced commercially until the 1950s. Although titanium is
expensive, its high strength-to-weight ratio and corrosion resistance at room and
elevated temperatures makeit attractive for many applications, including aircraft; jet
engines (see Fig. 6.1); racing cars; golf clubs; chemical, petrochemical, and marine
components; submarinehulls;armor plate; and medicalapplications,such as
orthope-dic implants (Table 6.10). Titanium alloys have been developed for service at 550°C
for longperiods of time and atup to 750°C for shorterperiods.
Unalloyed titanium, known as commercially pure titanium, has excellent
corrosion resistance for applications where strength considerations are secondary.
Aluminum, vanadium, molybdenum, manganese, andother alloying elements impart
propertiessuch as improved workability, strength, and hardenability.
The properties and manufacturing characteristics of titanium alloys are
ex-tremelysensitiveto smallvariationsinbothalloying and residual elements. Therefore, control of composition and processing are important, especially the prevention of
surface contamination by hydrogen, oxygen, or nitrogen during processing; these
elements cause embrittlement of titanium and, consequently, reduce toughness and
ductility.
The body-centered cubic structure of titanium (beta-titanium) is above 880°C
andis ductile, whereasits hexagonal close-packed structure (alpha-titanium) is
some-what brittle and is very sensitive to stress corrosion. A variety of other structures (alpha, near-alpha, alpha-beta, andbeta) can beobtainedbyalloyingand heat
treat-ing, so thatthe properties can be optimized for specificapplications. Titanium
alu-minide intermetallics (TiAl and Ti3Al; see Section 4.2.2) have higher stiffness and lower density than conventional titanium alloys and can withstand higher tempera-tures.
Production. Orescontaining titanium first arereduced to titanium tetrachloride in
an arc furnace, then converted to titanium chloride in a chlorine atmosphere. This
compound is reduced furthertotitanium metal by distillation and leaching
(dissolv-ing). This sequence forms sponge titanium, whichis then pressed into billets,melted,
and poured into ingots tobe processed later into various shapes. The complexity of
these multistep thermochemical operations (the Kroll process developed in the
1940-1950s) adds considerably to the cost oftitanium. New developments in
elec-trochemical extraction processes are taking place to reduce the number of steps
involved and the energy consumption, thereby reducing the cost of producing titanium.
TABLE 6.I0
Properties andTypicalApplicationsofSelected Wrought TitaniumAlloysatVariousTemperatures
Ultimate Ultimate
Nominal tensile Yield Reduction tensile Yield
composition strength strength Elongation of area Temp. strength strength
(%) UNS Condition (MPa) (MPa) (°C) (MPa) (MPa)
99.5Ti R50250 Annealed 330 240 300 150 95
5Al, 2.5 Sn R54520 Annealed 860 810 300 565 450
6Al, 4V R56400 Annealed 1000 925 300 725 650
Solution + age 1175 1100 300 980 900
Section 6.8 Refractory Metalsand Alloys
6.8
Refractory Metals
and
Alloys
There are four refractory metals: molybdenum, niobium, tungsten, and tantalum.
These metals arecalledrefractory because oftheir high melting points. Althoughthey
were discovered about200 years ago and have been used as important alloying
ele-ments in steels and superalloys, their use as engineering metals and alloys did not
begin untilabout the 1940s. More than mostothermetals and alloys, the refractory
metals maintain their strength atelevatedtemperatures. Therefore, they are of great
importance inrocket engines, gas turbines, and various otheraerospace applications;
in the electronic, nuclear-power, and chemical industries; and as tool and die
materi-als. The temperaturerange for some of these applicationsis on the order of 1100 to 2200°C, where strength and oxidation are ofmajor concern.
6.8.l
Molybdenum
Molybdenum (Mo) is asilverywhite metal discovered inthe 18th century and has a
high melting point, high modulus of elasticity, good resistance to thermal shock, and good electrical and thermal conductivity. Molybdenum is used in greater amounts than any other refractorymetal, in applicationssuch as solid-propellant rockets, jet
engines, honeycomb structures, electronic components, heating elements, and dies
for' die casting. The principal alloying elements for molybdenum are titanium
andzirconium. Molybdenum is itself also an important alloying element in cast and
wrought alloy steels and in heat-resistant alloys, imparting strength, toughness, and corrosion resistance. A major limitation of molybdenum alloys is their low
resist-ance to oxidation at temperatures above 500°C, which necessitates the use of
pro-tective coatings.
Production. The main source ofmolybdenum is the mineral molybdenite
(molyb-denumdisulfide). The ore first is processed and the molybdenum is concentrated;
later, it is chemically
reduced-first
with oxygen and then with hydrogen.Powder-metallurgy techniques also are used to produce ingots for further processing into various shapes.
6.8.2
Niobium (Columbium)
Niobium (Nb, for niobium, after Niobe, the daughter of the mythical Greek king
Tantalus) was first identified in 1801; it is also referred to as columbium (after its
source mineral, columbite). Niobium possesses good ductility and formability and
has greater oxidation resistance than other refractorymetals. With various alloying elements, niobium alloys can beproduced with moderatestrength and good fabrica-tion characteristics. These alloys are used in rockets and missiles and in nuclear,
chemical, and superconductor applications. Niobium is also an alloying element in
various alloys and superalloys. The metal is processed from ores by reduction and refinement and from powder by melting and shaping into ingots.
6.8.3 Tungsten
Tungsten (W for u/olfrarn, its European name, and from its source mineral, wolframite; in Swedish, tung means “heavy” and sten means “stone”) was first
identified in1781; it is the most abundant of all the refractorymetals. Tungsten has the highest melting point ofany metal (3410°C). As aresult, itis notable for itshigh
strength at elevated temperatures. However, ithas high density (hence it is used for balancing weights and counterbalances in mechanical systems, including
self-wind-Chapter6 Nonferrous Metalsand Alloys: Production,General Properties, and Applications
ing watches), is brittle atlow temperatures, and offers poorresistance tooxidation.
As an alloying element, tungsten impartsstrength and hardness to steels at elevated
temperatures.
Tungsten alloys are used for applications involving temperatures above
165O°C, such as nozzle throat liners in missiles and in the hottest parts of jet and
rocket engines, circuit breakers, welding electrodes, tooling for electrical-discharge machining, and spark-plug electrodes. The filament Wire in incandescent light bulbs
(Section 1.1) is made of pure tungsten and is produced by the use of
powder-metallurgy andwire-drawing techniques. Tungsten carbide, with cobaltas a binder for the carbide particles, is one of the most important tool and die materials. Tungsten is processed from oreconcentrates bychemical decomposition and is then
reduced. It is further processed by povvder-metallurgy techniques in a hydrogen
atmosphere.
6.8.4
Tantalum
Identified in 1802, tantalum (Ta, afterthe mythical Greek king, Tantalus) is
charac-terized by its high melting point (3000°C), high density, good ductility, and
resist-ance to corrosion. However, it has poorchemical resistance at temperatures above
15 O°C.Tantalum is usedextensively inelectrolytic capacitors and invarious compo-nentsinthe electrical, electronic, and chemical industries; italso is used forthermal applications, such as in furnaces and in acid-resistant heat exchangers. A variety of
tantalum-based alloys are available in many forms for use inmissiles and aircraft.
Tantalum also is used as an alloying element.It is processed bytechniques similar to
thoseused for processing niobium.
6.9
Beryllium
Steel gray incolor, beryllium (Be, from the ore beryl) has a high strength-to-Weight
ratio. Unalloyed beryllium is used in rocket nozzles, space and missile structures,
aircraft disc brakes, and precisioninstruments andmirrors. It is used innuclear and X-ray applications because of its low neutron absorption. Beryllium is also an
al-loying element, and its alloysof copperand nickel areemployed invarious applica-tions, including springs (beryllium copper), electrical contacts, and nonsparking
tools foruse in such explosiveenvironments as mines andmetal-powder production
(Section 17.2.3). Beryllium and its oxide are toxic; their associated dust and fumes
should not be inhaled.
6.l0
Zirconium
Zirconium (Zr) is silvery in appearance;it has goodstrength and ductility atelevated
temperatures and has good corrosion resistance because of an adherent oxide film.
Zirconium is used in electroniccomponents and in nuclear-power reactor
applica-tions because of its low neutron absorption.
6.1 I
Low-melting
Alloys
Low-melting alloys are so named because oftheir relatively lowmelting points. The
Section 6.11
6.ll.l
LeadLead (Pb, afterplumbum, the root of the word “plumber”) has characteristic prop-ertiesof highdensity, resistance to corrosion (byvirtue ofthe stable lead-oxidelayer
that forms to protect the surface), softness, low strength, ductility, and good
work-ability. Alloying it with various elements (such as antimony and tin) enhances its
desirable properties, making it suitable for piping, collapsible tubing, bearing alloys
(Babbitt), cablesheathing, foil (asthin as 0.01 mm), roofing, and lead-acid storage batteries. Lead also is used for damping sound and vibrations, radiation shielding against X-rays, ammunition, as weights, and in the chemical industry. Because it
creeps even at room temperature, the use of lead for load-bearing applications is very limited.
The oldest known lead artifacts were made in about 3000 B.C. Lead pipes
made bythe Romansand installed inthe Roman baths in Bath, England, two
mil-lenniaago are still in use.Lead is also an alloying element insolders, steels, and cop-per alloys; itpromotes corrosion resistance and machinability. An additional use of
lead is as a solid lubricant forhot-metal-forming operations. Because of itstoxicity,
however, environmental contamination by lead (causing lead poisoning) is a major
concern; majorefforts are currently being made to replace lead with other elements
(such as lead-free solders, Section 32.3.1). The most important mineral source of
lead is galena (PbS); it is mined, smelted, and refined bychemical treatments.
6.l l.2 Zinc
Zinc (Zn), is bluish whitein color and is the metalthat is fourth most utilized
indus-trially, after iron, aluminum, and copper. Although its existence was known for
many centuries, zinc was not developed until the 18th century. It has three major
uses: (1) for galvanizing iron, steel sheet, and wire, (2) as an alloy inother metals,
and (3) as a material in castings.
In galvanizing, zinc serves as an anode and protects the steel (cathode) from corrosive attack should the coating be scratched or punctured. Zinc also is used
as an alloying element; brass, for example, is an alloy of copper and zinc. Major
alloying elements in zinc-based alloys are aluminum, copper, and magnesium;they
impart strength and provide dimensional control during casting of the metal.
Zinc-based alloys are used extensively in die casting for making such products as fuel
pumps and grills for automobiles, components for household appliances such as
vacuum cleaners and washing machines, kitchen equipment, various machinery parts, and photoengraving equipment. Another use forzinc is in superplastic alloys
A very fine grained 78% Zn-22% Al sheetis a common example of a superplastic
zinc alloy that can be formed by methods used for forming plastics or metals.
Production. A number of mineralscontainingzinc are found in nature. The
prin-cipal mineral sourceis zinc sulfide, also called zincblende. Theore first is roasted in
air and converted tozinc oxide. Itthenis reduced tozinc either electrolytically (with
the use of sulfuric acid) or by heating it in a furnace with coal (which causes the
molten zinc to separate).
6.l l.3 Tin
Although used in small amounts compared with iron, aluminum, or copper, tin
Sn, from the Latin stannum is an im ortant metal. The most extensive use of tin
p
a silver-white> lustrous metal is as a Protective coating on steel sheets tin lates
Chapter6 Nonferrous Metalsand Alloys: Production, GeneralProperties, and Applications
used inmaking containers (tin cans) for food and forvarious other products. The
low shear strength of the tin coatings on steel sheets improves deep drawability
(Section 16.7.1) and performance in general pressworking. Unlike galvanized
steels, if thiscoating is puncturedor destroyed, the steelcorrodes because the tinis
cathodic.
Unalloyed tinis used in such applications as a lining materialfor water
distil-lation plants and as a molten layer of metal in the production of float glass plate
(Section 18.3.1). Tin-based alloys (also called white metals) generally contain
cop-per, antimony, andlead. The alloying elements imparthardness, strength, and corro-sion resistance. Tin is an alloying element for dental alloys and for bronze
(copper-tin alloy), titanium, and zirconium alloys. Tin-lead alloys are common
soldering materials, witha wide range of compositions and melting points.
Because of theirlow friction coefficients (which result from low shear strength
and low adhesion), some tin alloys are used as journal-bearing materials. These alloys are knownas babbitts (after I. Babbitt, 1799-1862) and contain tin,copper, and antimony. Pewter, an alloy of tin, copper, and antimony, was developed inthe
15th century and has beenused for tableware, hollowware, and decorative artifacts.
Organpipes aremade oftinalloys. The most important tin mineralis cassiterite (tin
oxide), which is of lowgrade. The oreis mined, concentratedby various techniques, smelted, refined, and cast into ingots forfurtherprocessing.
6.l2
Precious Metals
The most important precious (costly) metals, also called noble metals, are the
following:
° Gold (Au, from the Latin aurum) is soft and ductile and has good corrosion resistance at any temperature. Typical applications include jewelry, coinage, reflectors, gold leaf for decorative purposes, dental work, electroplating, and electricalcontacts and terminals.
° Silver (Ag, fromthe Latinargentum) is ductileand has thehighestelectrical and
thermal conductivity of any metal (Table 3.2). However, it develops an oxide
film that affects its surface characteristics and appearance. Typical applications
for silverinclude tableware, jewelry, coinage, electroplating, electrical contacts,
solders, bearing linings, and food and chemical equipment. Sterling silz/er is an
alloy of silver and 7.5% copper.
° Platinum (Pt) is asoft, ductile,grayish-white metal thathas goodcorrosion
resist-ance even at elevatedtemperatures. Platinumalloys are used as electricalcontacts;
for spark-plug electrodes; as catalysts for automobile pollution-control devices;
in filaments and nozzles; in dies for extruding glass fibers (Section 18.3.4), in
thermocouples;andin jewelryand dentalwork.
6.13
Shape-memory
Alloys
(Smart
Materials)
Shape-memory alloys are unique inthat, after being plastically deformed into vari-ous shapes at room temperature, they return to their original shape upon heating. For example, a piece of straight wire made of such materialcan be wound into the
Section6 15 Metal Foams
to the original straightshape. Shape-memory alloys can be used to generate motion and/or force in temperature-sensitive actuators. The behavior of these alloys, also
called smart materials, can bereversible; thatis, the shape canswitch back andforth
repeatedly upon application and removal of heat. A typical shape-memory alloy
is 55% Ni-45% Ti (Nitmol). Other such alloys are copper-aluminum-nickel,
copper-zinc-aluminum, iron-manganese-silicon, and titanium-nickel-hafnium.
Shape-memory alloys generally have such properties as good ductility, corrosion resistance, and high electrical conductivity.
Applications of shape-memory alloys include varioussensors, eyeglass frames, stents for blocked arteries, relays, pumps, switches, connectors, clamps, fasteners,
and seals. As an example, a nickel-titanium valve has been made to protectpeople
from being scalded insinks, tubs, and showers. It is installed directly into thepiping
system and brings the water flow down toatrickle within 3 seconds after the water
temperature reaches 47°C. New developments include thin-film shape-memory
al-loys deposited on polished silicon substrates for use in microelectromechanical
(MEMS) devices (see Chapter 29).
6.|4
Amorphous
Alloys
(Metallic Glasses)
A class of metal alloys that, unlike metals, do not have a long-range crystalline
structure is called amorphous alloys; these metals have no grain boundaries, and their atoms are packed randomly and tightly. The amorphous structure first was
obtained in the late 1960s by the extremely rapid solidification of a molten alloy
(Section 11.6). Because theirstructure resemblesthat ofglasses, these alloysare also
calledmetallic glasses. Amorphousalloys typicallycontain iron, nickel,and chromium,
which arealloyed with carbon, phosphorus, boron, aluminum, and silicon.Theyare
available aswire, ribbon, strip, and powder: One application is for faceplate inserts on golf-club heads; this alloy has a composition of zirconium, beryllium, copper, titanium, and nickel and is made by die casting. Another application is in hollow aluminum baseball bats coated with a composite of amorphous metal by thermal sprayingand is saidto improve the performance of the bat.
Amorphous alloys exhibit excellent corrosion resistance, good ductility, high
strength, and very low magnetic hysteresis. The latter property is utilized in the
production of magnetic steel cores for transformers, generators, motors, lamp
bal-lasts, magnetic amplifiers, and linear accelerators. The low magnetic hysteresis
loss provides greatly improved efficiency; however, fabrication costs are
signifi-cant. Amorphous steels are being developed with strengths twice those of
high-strength steels, with potential applications in large structures; however, they are
presently cost prohibitive. A major application for the superalloys of rapidly
solid-ified powders is the consolidation into near-net shapes for parts used inaerospace
engines.
6.l
5Metal
Foams
Metal foams are material structures where the metal consists of only 5 to 20% of the structure’s volume, as shown in Fig. 6.3. Usually made of aluminum alloys (but
|68 Chapter6 Nonferrous Metalsand Alloys: Production, GeneralProperties, and Applications
W
yy*
FIGURE 6.3 Microstructure
ofa metal foam usedin ortho-pedic implants to encourage
boneingrowth. Source:
Cour-tesy ofZimmer, Inc.
KEY
TERMS
into molten metal and tapping the froth that forms at the surface; this froth then
solidifies into afoam. Other approachesto producing metal foam include (a)
chem-ical vapor deposition (Section 34.6.2) onto a carbon foam lattice, (b) depositing metal powders from a slurry onto a polymer foam lattice, followed by sintering
(Section 17.4) to fuse the metals and burn off the polymer, (c) doping molten or
powder metals (Chapter 17) with titanium hydride (TiH2), which then releases
hydrogen gas at the elevated casting or sintering temperatures, and (d) pouring molten metal into a porous salt and, upon cooling, leaching out the salt with acid.
Metal foams have unique combinations ofstrength-to-density and stiffness-to-density ratios, although these ratios are not as high as the base metals themselves.
However, metal foamsare very lightweight and thus areattractivematerials for
aero-space applications. Because of their porosity, other applications ofmetal foams are
filters and orthopedic implants. Recent developments include
nicl<el-manganese-gallium metal foams with shape-memory characteristics (Section 6.13).
SUMMARY
° Nonferrous metals and alloys includea very broad range of materials. The most
common are aluminum, magnesium, and copper and their alloys, which havea
wide rangeof applications. For highertemperature service, nonferrous metals
in-clude nickel, titanium, refractory alloys (molybdenum, niobium, tungsten, tanta-lum), and superalloys. Other nonferrous metal categories include low-melting alloys (lead, zinc,tin) and precious metals (gold, silver, platinum).
° Nonferrous alloys havea wide variety of desirable properties, such as strength,
toughness, hardness, and ductility; resistance to high temperature, creep, and
oxidation; awide range of physical, thermal,and chemical properties; and high
strength-to-weight and stiffness-to-weight ratios (particularly for aluminum
and titanium). Nonferrous alloys can be heat treated to impart certain desired
properties.
° Shape-memory alloys (smart materials) have unique properties, with numerous
applicationsin a varietyof productsand manufacturing operations.
° Amorphous alloys (metallic glasses) have several properties that are superior to
othermaterials, available invarious forms, they have numerous applications.
° Metal foams are very lightweight and thus are attractive for aerospace as well as
various other applications.
° As with all materials, the selection ofa nonferrousmaterial fora particular
appli-cation requires a careful consideration of many factors, including design and
servicerequirements, long-term effects,chemical affinity to othermaterials,
envi-ronmental attack, and cost.
Amorphous alloys Low-melting alloys Precious metals Smelting
Babbitts Metal foam Pyrometallurgy Superalloys
Brass Metallic glasses Refractorymetals Temper designation
Bronze Nonferrous Shape-memory alloys
BIBLIOGRAPHY
Qualitative Problems I69
ASM Handbook, Vol. 2: Properties and Selection:
Nonferrous Alloys and Special-Purpose Materials,
ASM International, 1990.
ASMSpecialtyHandbook:Aluminum andAluminumAlloys,
ASMInternational, 1993.
ASMSpecialtyHandbook: Copper and CopperAlloys, ASM
International, 2001.
ASM Specialty Handbook: Heat-Resistant Materials, ASM
International, 1997.
ASM Specialty Handbook: Magnesium and Magnesium
Alloys, ASM International, 1999.
ASM SpecialtyHandbook:Nickel, Cobalt, and TheirAlloys,
ASM International 2000.
Cardelli, F., MaterialsHandbook: AConcise Desk Reference,
2nded., Springer,2008.
Donachie, MJ. (ed.), Titanium:A TechnicalGuide, 2nd ed.,
ASM International, 2000.
REVIEW
QUESTIONS
Donachie, M.]., and Donachie, S.].,Superalloys:A Technical
Guide, 2nd ed., ASM International, 2002.
Farag, M.M., Materials Selection for Engineering Design, Prentice Hall, 1997.
Fremond, M., and Miyazaki, S., Shape-Memory Alloys,
Springer Verlag, 1996.
Kaufman, ].G., Introduction to Aluminum Alloys and
Tempers,ASM International, 2000.
Lagoudas, D.C. (ed.), Shape Memory Alloys: Modeling and
EngineeringApplications,Springer, 2008.
Leo, D.]., Engineering Analysis of Smart Material Systems,
Wiley, 2007.
Lutjering, G., and Williams, ].C., Titanium, 2nd ed.,
Springer, 2007.
6.l. Given the abundanceof aluminum in the earth’s crust, explain why itis more expensive thansteel.
6.2. Why is magnesium often used as a structural material
in power hand tools? Why are its alloys usedinstead ofpure magnesium?
6.3. Whatare themajor usesofcopper? Whatare the
alloy-ingelements in brass and bronze,respectively?
6.4. Whataresuperalloys? Why are theyso named?
6.5. What properties of titanium make itattractive foruse
in race-car and jet-engine components? Why is titanium not
used widelyforengine componentsin passengercars?
6.6. Whichproperties of each of the major refractory
met-als define their most useful applications?
6.7. What are metallic glasses? Why is the word “glass” used forthese materials?
QLIALITATIVE
PROBLEMS
6.8. Whatis thecompositionof (a)babbitts, (b) pewter, and
(C) sterling silver?
6.9. Name the materials described in thischapter thathave
the highest(a) density, (b) electrical conductivity, (c) thermal
conductivity,(d) strength,and (e) cost.
6.|0.
6.lI. Describe the advantages to using zinc as a coating for
steel.
Whatare themajorusesofgold, otherthaninjewelry?
6.l2. What are nanomaterials? Why are they being
devel-oped?
6.|3. Why are aircraft fuselages made of aluminum alloys,
even though magnesiumis thelightest metal?
6.|4. Explain why cooking utensils generally are made of
stainless steels, aluminum,or copper.
6.I5. Would itbeadvantageous toplotthedatain Table 6.1
in terms of cost per unit weight rather than cost per unit volume? Explainand give some examples.
6.I6. Comparethe contents ofTable 6.3 with those in
vari-ous other tables and data on materials in this book, then
comment on which of the two hardening processes (heat
treating and work hardening) is more effective in improving
the strength ofaluminum alloys.
6.l7. Whatfactors other than mechanicalstrength shouldbe
considered in selectingmetals and alloysfor high-temperature
applications? Explain.
6.|8. Assume that, for geopolitical reasons, the price of
copper increases rapidly. Name two metals with similar
mechanical and physical properties that can be substituted forcopper. Comment onyour selection and anyobservations youmake.
|70 Chapter6 Nonferrous Metalsand Alloys: Production,General Properties,andApplications
6.l9. If aircraft, such as a Boeing 757, are made of 79%
aluminum, why are automobiles made predominantly of steel?
6.20. Portable (notebook) computers and digital cameras
can have their housing madeofmagnesium. Why?
6.2l. Most household wiring is made of copper wire. By
contrast, grounding wire leading to satellite dishes and the
like ismade ofaluminum. Explainthe reason.
QUANTITATIVE
PROBLEMS
|]6.23.
A simply supported rectangular beam is 30 mm wide and 1 m long, and it is subjected to a vertical load of40 kg at its center. Assume thatthis beam could be made of
any ofthe materials listed in Table 6.1. Selectthree different
materials, and foreach,calculate the beam heightthatwould
cause each beam to have the same maximum deflection. Calculate the ratio of thecostforeach of the three beams. 6.24. Obtain a few aluminum beverage cans, cut them,and measure their wall thicknesses. Usingdata in thischapter and simple formulas for thin-walled, closed-end pressure vessels, calculate themaximum internal pressure these cans can
with-stand before yielding. (Assumethat the can is a thin-walled,
closed-end, internallypressurized vessel.)
SYNTHESIS, DESIGN,
AND
PROIECTS
6.22. The example in this chapter showed the benefits of
making cars from aluminum alloys. However, the average
amount ofsteel in carshas increased in the past decade. List
reasonstoexplainthese two observations.
6.26. Beverage cans usually arestacked ontopofeach other
in stores. Usethe information fromProblem 6.24, and,
refer-ring to textbooks on the mechanics of solids, estimate the
crushing load eachof these canscan withstand.
|]6.27.
Using strength and density data, determine theminimum weight of a 900-mm long tension member that
must support 340 kg ifitis manufactured from (a) 3003-O
aluminum, (b) 5052-H34 aluminum, (c) AZ31B-F
magne-sium, (d) any brassalloy, and (e) any bronze alloy.
|]6.28.
Plot the following for the materials described inthischapter: (a) yieldstrengthvs.density, (b)modulus of
elas-ticity vs. strength, (c) modulus of elasticity vs. relative cost, and (d) electrical conductivityvs. density.
6.29. Because of the number of processes involved in
mak-ingmetals, the cost of raw materials depends on the
condi-tion (hotor cold rolled), shape (plate, sheet, bar, tubing), and
size of the metals. Make a survey of the technical literature,
obtainprice lists or getintouch with suppliers,and preparea
listindicatingthecostper 100 kgofthe nonferrous materials
described in this chapter, available in different conditions,
shapes, and sizes.
6.30. The materials described in this chapter have
numer-ous applications. Make a survey ofthe available literaturein
the bibliography,and preparealistofseveral specific parts or
components and applications, indicatingthe types of
materi-als used.
6.3I. Name products thatwouldnot have beendeveloped to
their advancedstages (as we findthem today) ifalloys having
high strength, highcorrosionresistance, and high creep resist-ance (all at elevatedtemperatures) had notbeen developed.
6.32. Assume that you are the technical salesmanager ofa
company that produces nonferrous metals. Choose any one
of the metals and alloys described inthis chapter, andprepare
abrochure, including someillustrations, foruseas sales
liter-atureby your staff in their contact with potentialcustomers.
6.33. Give some applications for (a) amorphous metals,
(b) precious metals, (c) low-melting alloys, and (d)
nano-materials.
6.34. Describe the advantages of making products with
multilayermaterials. (For example, aluminum bonded to the
ER PT
A
CHPolymers:
Structure,
General
Properties,
and Applications
° Polymers display a wide range of properties and have several advantages over metallic materials, including lowcost, goodperformance, andease of manufac-turing; for these reasons, polymers continue to be among the most commonly
used materials.
° This chapter first describes the structure of polymers, the polymerization process, crystallinity, andthe glass-transition temperature.
° Mechanical properties and how theyare affected bytemperature and deforma-tion rateare then discussed.
° The chapter describes the two basic types of polymers: thermoplastics and
thermosets.
° Thermoplastics allow a basic manufacturingprocessof heating them untilthey
soften or melt, and then shaping them into the desiredproduct.
° The process forthermosets is to form the precursors to a desired shape and
then setitthrough polymerization or cross-linking between polymer chains.
° The chapter also describes the properties and uses of elastomers, or rubbers.
° The general properties, typical applications, advantages, and limitations of
polymers are discussed throughout the chapter, with several specific examples
given.
1.l
Introduction
Theword plastics first wasused as a nounaround 1909 and commonlyis employed
as a synonym for polymers, a termfirst used in 1866. Plastics areunique in thatthey
haveextremely large molecules (macromolecules orgiant molecules). Consumer and industrial products made of plastics include food and beverage containers,
packag-ing, signs, housewares, housings for computers and monitors, textiles (clothing),
medical devices, foams, paints, safety shields, toys, appliances, lenses, gears,
elec-tronic and electrical products, and automobilebodies and components.
Because oftheir many unique and diverse properties, polymers increasingly have
replaced metallic components in applications such as automobiles, civilian and
7.I Introduction |7I 7.2 TheStructureof Polymers |73 7.3 Thermoplastics |80 7.4 Thermosetting Plastics |84 7.5 AdditivesinPlastics |84 7.6 GeneralProperties andApplicationsof Thermoplastics |85 7.7 General Properties and Applicationsof Thermosetting Plastics |88 7.8 Biodegradable Plastics |90 7.9 Elastomers (Rubbers) I9l EXAMPLES:
7.I Dental and Medical
BoneCement |77 7.2 UseofElectrically ConductingPolymers inRechargeable Batteries |83 7.3 Materialsfora RefrigeratorDoor Liner |89 l7l
Chapter 7 Polymers: Structure. GeneralProperties, andApplications
militaryaircraft, sporting goods,toys, appliances, andoffice equipment. These
substi-tutionsreflectthe advantages ofpolymersintermsof thefollowing characteristics:
° Relatively lovv cost (see Table 6.1) and ease of manufacture
° Corrosion resistance and resistance to chemicals
° Low electrical and thermal conductivity
° Lovv density
° High strength-to-Weight ratio (particularly when reinforced) ° Noise reduction
° Wide choice of colorsand transparencies
° Ease ofmanufacturing and complexity ofdesignpossibilities
° Other characteristicsthatmay or maynotbedesirable (depending on the
applica-tion), such as low strength and stiffness (Table 7.1), high coefficient of thermal
expansion, low useful-temperature
range-up
to about350°C-and
lowerdi-mensional stabilityinserviceover aperiod of time.
The Wordplastic is from the Greekvvordplastilzos, meaning “capable of being
molded and shaped.” Plastics can be formed, machined, cast, and joined into vari-ous shapes With relative ease. Minimal additional surface-finishing operations, if
any at all, are required; this characteristic provides an important advantage over
metals. Plastics are available commercially as film, sheet, plate, rods, and tubing of
various cross-sections.
The earliest polymers were madeofnatural organic materials from animal and vegetable products; cellulose is the most common example. By means of various chemical reactions, cellulose is modified intocellulose acetate, used inmaking sheets
TABLE 1.|
RangeofMechanical Properties for Various Engineering Plastics atRoom
Temperature
Young’s
modulus(E) Elongation Poisson’s
Material UTS (MPa) (GPa) l%l ratio,1/
Acrylonitrile-butadiene- 28-55 1.4-2.8 75-5
-styrene (ABS) ABS, reinforced 100 7.5-
0.35 Acetal 55-70 1.4-3.5 75-25 -Acetal, reinforced 135 10-
0.35-0.40 Acrylic 40-75 1.4-3.5 50-5 -Cellulosic 10-48 0.4-1.4 100-5 -Epoxy 35-140 3.5-17 10-1 -Epoxy, reinforced 70-1400 21-52 4-2 -Fluorocarbon 7-48 0.7-2 300-100 0.46-0.48 Nylon 55-83 1.4-2.8 200-60 0.32-0.40 Nylon, reinforced 70-210 2-10 10-1 -Phenolic 28-70 2.8-21 2-0 -Polycarbonate 55-70 2.5-3 125-10 0.38 Polycarbonate, reinforced 110 6 6-4 -Polyester 55 2 300-5 0.38 Polyester, reinforced 110-160 8.3-12 3-1 -Polyethylene 7-40 0.1-1.4 1000-15 0.46 Polypropylene 20-35 0.7-1.2 500-10_
Polypropylene,reinforced 40-100 3.5-6 4-2 -Polystyrene 14-83 1.4-4 60-1 0.35 Polyvinyl chloride 7-55 0.014-4 450-40-Section 7.2 The Structureof Polymers H ill s * `i fif C Plasticizers Stabilizers 3 Colorants
""}
Flameretardants I Lubricants :` i t'i "i" `
`
I Thermop|astics:Acrylics,ABS, nylons_ _ gg ' _ polycarbonates, polyethylenes
Kjéfgr
`ii Heat, PV€‘SSUfe» polyvinylchloride etcmars Polymer
ren Catalyst <rrri” “
~
ee <rr» Thermosets:Epoxies,phenolicsi : polyimides, etc.
' |
|:>O|ymeliZatiOn; Amoréhous E Elastomers: Natural and synthetic rubbers
Condengatign, PamyCrystamne : silicones, polyurethanes etc
a°ld'l'°“ Linear Cross-linking
Branched Homopolymer Copolymer Terpolymer
FIGURE 1.l Outline ofthe topics described in Chapter 7.
for packaging and textile fibers such as rayon; cellulose nitrate, for plastics and explosives; and varnishes. The earliest synthetic (manmade) polymer was phenol
formaldehyde, a thermoset developed in 1906 and called Bakelite (a trade name, afterL.H. Baekeland, 1863-1944).
The development of modern plastics technology began in the 1920s when the
raw materials necessary for making polymers were extractedfrom coal and petrole-umproducts. Ethylene was the first example of such a raw material; it became the
building block for polyethylene. Ethylene is the product of the reaction between acetylene and hydrogen, and acetyleneis the product of the reaction between coke and methane. Commercial polymers, such as polypropylene, polyvinyl chloride,
polymethylmethacrylate, polycarbonate, and others, are all made in a similar
man-ner; thesematerials are known assynthetic organic polymers.
An outlineofthe basic process for making various synthetic polymers is given
inFig. 7.1. Inpolyethylene, onlycarbonand hydrogen atoms areinvolved, butother
polymer compounds can be obtained byincluding chlorine, fluorine, sulfur, silicon,
nitrogen, and oxygen. As a result, an extremely wide range of polymers--having
among them an equally wide range of
properties-has
beendeveloped.This chapter describes the relationship of the structure of a polymer to its
properties and behavior, during both manufacturing and its service life under vari-ous physical and environmental conditions. This chapter also describes the
proper-ties and engineering applications of plastics, rubbers, and elastomers. Reinforced plastics and composite materials are described in Chapter 9, and processing meth-ods for plastics and reinforced plastics inChapter 19.
7.2
The
Structure
of
Polymers
The properties ofpolymers depend largely on the structures of individual polymer molecules, molecule shape and size, and the arrangement of molecules to form
