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Wrought and Sheet: Overview

Technology Innovation in AluminumProductsRobert E. Sanders, Jr.

In 2001, the aluminum industry continues to benefitfrom technical innovations made in alloydevelopment, product-manufacturing technologies,and processing equipment over the last century.This paper examines the top ten alloy, product, andprocess developments that have shaped the industry production methods and markets. The inter-relationships among the alloy development, processinnovations, and markets are highlighted. Omittedare details about patent literature or theinception of many technologies; the major criterion

for placement on the list was impact on the totalindustry.

INTRODUCTIONThe aluminum industry has evolved over the past 100years from the limited production of alloys andproducts to the high-volume manufacture of a widevariety of products. Today U.S. aluminumproduction includes roughly 5.6 million tonnes offlat-rolled products, 1.7 million tonnes of

extrusions and tube, and 2.4 million tonnes ofingot/castings.1 These products are used in a widevariety of markets, including building andconstruction, transportation, and packaging.Markets also exist for such products as electricalconductors (EC), forgings, rod, wire, bar, andpowders and pastes, as shown in the ther category in Figure1.

Following is an analysis of ten innovations thatinfluenced aluminum production methods and markets.Although Alcoa was the source of much of thehistorical perspective, two factors may excuse thisto some degree:

The following article appears in the journal JOM,53 (2) (2001), pp. 21-25

TABLE OF CONTENTS INTRODUCTION

DIRECT-CHILL CASTING HEAT-TREATABLE ALLOYS TWO-PIECE BEVERAGE CAN ALUMINUM EXTRUSION CONTINUOUS MOLTEN METAL

TREATMENT ALLOY 6061 ELECTRICAL CONDUCTORS CONTINUOUS CASTING SHAPE-CASTING ALLOY A356 EXTRUSION PRESS QUENCHING CONCLUSION ACKNOWLEDGEMENTS References

Page 1 of 12Technology Innovation in Aluminum Products

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Many of these developments took place beforethe birth of Alcoa major competitors.

While Alcoa early technical history is welldocumented, little was found in the openliterature on early European developments.

DIRECT-CHILL CASTINGCasting in the early days of aluminum productionconsisted of making 45 kg ingots in steel-tilt

molds.2 As shown in Figure 2, the family of alloysthat could be offered to aluminum customers wasgrowing by the 1920s. Supplies were limited bydifficulties with casting and ingot quality,however. The tilt molds suffered frommacrosegregation, porosity, and a tendency towardsevere shrinkage cracking when the alloy contentincreased. Alcoa fabricating plants coped withcasting inefficiency, poor ingot quality, and sizelimitations. Recovery losses were realized as thetilt molds had to be calped substantially toremove undesirable surface segregation.

William T. Ennor, of Alcoa Massena operations,devised the idea of directly impinging water on thesolidified shell of an ingot as it was cast. Usingthe direct chill (DC) process, it was possible to

drop the ingot continuously and avoid theturbulence associated with pouring metal into the

old tilt molds. Ennor patent3 provided the basisfor modern DC-casting technology, which wasintroduced into virtually all of Alcoa plantsduring the 1930s. The plants built by Alcoa for thewar effort incorporated this technology to makealuminum products for the aircraft industry. In1951, just after Alcoa Davenport works was completed, the largest aluminum

ingot fabricated was approximately 3.1 tonnes.4 During the 1950s, DC ingots wereavailable to make the large products needed by the aerospace, marine, and

transportation industries. Size increases continued over the yearsoday sheetingots may reach 15.5 tonnes and extrusion billet are produced as large as 1.2 min diameter. Figures 3a and 3b show typical cast sheet ingot and extrusion logsused in today aluminum industry.

In addition to allowing for larger ingots, DC casting helped improve productcharacteristics. Figure 4 shows the advancements in average mechanical propertiesand fatigue-endurance limit for alloys 2024 and 2017 as DC casting became the

standard within the U.S. aluminum industry.5 On the process side, it becamenecessary to re-engineer the downstream paths for some products. Alloy 3003 tilt-mold ingots, which cooled extremely slowly after solidification, required onlymodest thermal treatments to produce fine-grained products. However, the morerapid solidification of DC ingots resulted in significantly more manganese insolution as well as problems with coarse grain size. W.A. Anderson and others

Figure 1. Distribution ofaluminum shipments by (a-top)major market and (b-bottom)product form in major U.S.markets (based on 1999information).1



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solved those problems by applying high-temperature homogenization practices tothe ingot.

As the product-size capabilities increased with DC casting, so did the capabilityto develop new alloys, such as high-strength alloy 7075, introduced during WorldWar II. In the 1950s, new markets for shipbuilding required large ingots ofhigher magnesium 5xxx alloys such as 5086 and 5083. Other high-magnesium alloys,5082 and 5182, were developed in conjunction with horizontal DC casting in the1960s to supply the growing can-sheet market. Today complex, higher solute 2xxxand 7xxx alloys could certainly not be cast in the sizes needed for aerospaceapplications without high quality DC ingot. Neither could the coils of 3xxx or5xxx alloy can sheet be produced in the economic sizes demanded by the beverage-can industry.

HEAT-TREATABLE ALLOYSMuch has been written about the accidental discovery

of aluminum alloys heat-treatable capability 6,7 byGerman researcher A. Wilm in 1908. During World WarI, the Germans produced Duralumin for 80 airships

ore than 726 tonnes in one year.8Alcoa obtained therights to Wilm patent after World War I and beganresearch that led to alloys such as 25S (2025), 14S(2014), and aluminum-magnesium-silicon alloy 51S(6051), which were easier to fabricate than

Duralumin. Forged aluminum propellers were used onairplanes as early as 1922. By 1936, the major heat-treatable systems, aluminum-magnesium-silicon,aluminum-magnesium-copper, and aluminum-magnesium-

zinc, had been mapped out by researchers.9

With its improved strength, aluminum played a keyrole in the development of higher-performance

aircraft.10 The 2xxx (aluminum-copper) alloys quicklyreached a plateau with the development of 24S (2024)in 1933, in which the aluminum-magnesium-copper

phase diagram was exploited for maximum solubility.Because of their high strength, toughness, andfatigue resistance, modifications of 24S as well as

Figure 2. A timeline for aluminum product development.



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the original alloys are still widely used today foraircraft applications.

Alloy 75S (7075), developed during World War II,provided the high-strength capability not availablewith aluminum-magnesium-copper alloys. Modificationsto the base alloy composition resulted in highertoughness (alloys 7175 and 7475) while the T7xxtempers alleviated stress corrosion and exfoliationproblems inherent with the T6 temper. Thecomposition of alloy 7050 was designed to reducequench sensitivity in thick-section T7xx products.Additional development has extended the ability ofaluminum alloys to reduce weight and increaseaircraft performance. This development continuestoday, with the T77 tempers being utilized withspecial alloy compositions to attain levels of

strength and corrosion performance not matched byprevious materials.

TWO-PIECE BEVERAGE CANWith nearly 200 billion produced worldwide lastyear, aluminum cans are probably the most recognizedconsumer package in the world. More than 1/3 of theU.S. market for flat-rolled products is can sheet,with 1.9 million tonnes shipped in 1999. The demandfor can sheet has driven continuous improvements in

all aspects of the sheet production process,including technology to make recycled cans apreferred and economical source of metal for newcans.

Commercial cans initially were produced by CoorsBrewing Company from impact-extruded 1xxx-O slugsand, later, from relatively thick 3xxx-O sheet. Thereal breakthrough, though, came when ReynoldsAluminum developed draw-and- iron technology for the

use of hard (H18 and H19) tempers.11

This technologyallowed for considerable reduction in metalthickness, and, therefore, more economical,

lightweight cans. The technological aspects of can-making are described inReference 11.

Continuous innovation on a number of fronts has kept the can competitive againstother materials. After draw-and-iron technology reduced the can weight, the lidand tab became lighter also. Although alloy development contributed to the weightreduction, the most dramatic changes resulted from advances in can design andforming technology.

Perhaps equal in importance to the development of draw-and-iron technology werethe alloy and process innovations associated with the can lid. The development ofhigh-strength alloy 5182 in 1967 reduced the lid thickness to help make the cost

Figure 3. Typical DC cast (a-top)extrusion logs and (b-bottom)sheet ingot used in themanufacture of modern aluminumwrought products.

Figure 4. Improvement in minimummechanical properties and typicalfatigue performance of alloys2024 and 2017 in the T4 tempermade possible largely by usingDC-cast ingot for the manufactureof wrought products.



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of aluminum competitive with steel.12 Aluminum pull tabs were introduced as earlyas 1961, followed by the invention of tabs that remained attached to the cans,

which prevented the litter associated with detached tabs.13

When the growth of the can market sparked the need to find economies of scale insheet production, the aluminum industry re-invented the rolling process. Four-

high and, later, six-high rolling mills were needed to provide the tightthickness tolerances necessary as cans became lighter in weight. Tandem rollingmills, with as many as six stands, were used to reduce the number of rollingpasses. Improvements in rolling lubricants and control technologies enabled themills to roll sheet more consistently, faster, and with fewer cobbles. Todaycan sheet mills are often highly streamlined, producing large volumes ofconsistent can-body or lid-stock product.

Several highly specialized 3xxx and 5xxx (aluminum-magnesium-manganese) alloyshave been developed to meet the demands of the can industry. While the body-stockalloy and microstructure were customized particularly for the wall-ironing

process, the 5xxx lid alloy was developed for higher strength and goodformability after thermal exposure during the coating process. The need forproduct consistency also drove metallurgists to understand the rolling process,particularly the recrystallization mechanisms that govern the texture and earingbehavior (i.e., anisotropy) of can sheet. The pursuit of anisotropy control incan sheet elevated the level of physical metallurgy of non-heat-treatable

aluminum alloys over the last 20 years.11

Recycling technology, too, has had to keep pace with the demand for metal unitsused in the can market. Can-collection, baling, shredding, delacquering, andmelting technologies have all combined to improve the quality and economics ofbeverage-can recycling. Recycled aluminum cans continue to be a major source ofmetal for new cans. In 1999, over 862,000 tonnes of aluminum canswerecollected

intheUnitedStates,14 representing a recycling rate of 63.9%.

ALUMINUM EXTRUSIONThe hydraulic-extrusion press dates to the early19th century, well before the Hall-Hoult processfor making aluminum. During the 1800s, the processwas proven for lead and copper products. Althoughattempts by J.W. Hoopes of Alcoa in 1902 1904 toproduce conductor wire by a vertical-extrusion

process were unsuccessful,15 his experiences led theway for extrusion to be used for other products.

In 1905, Alcoa bought an extrusion press and hiredLouis de Cazenove to run it. The first aluminumextrusions were done at Alcoa Massena operations,but the equipment was moved to the New Kensington,Pennsylvania works, where commercial extruded shapes

were available after several years ofexperimentation. In this process, the aluminum wassolidified in the extrusion chamber and forcedvertically downward through a die. As the product



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size and extrusion pressures increased, theextrusion process was changed to use a horizontalpress. By 1923, Alcoa was using horizontal presses

with preheated billets.16

Today, the 1.5 million tonne market for aluminum

extrusions includes applications from building andconstruction to aerospace components. Extrudedproducts, which encompass virtually all of the alloyfamilies, range in size from millimeter-sizedmicrovoid hollow sections for heat exchangers tolarge wing structures for airplanes. Extrusions arealso the feedstock for aluminum wire, drawn tubing,and rod and bar products. Figures 5a and 5b showexamples of extruded products made in todayaluminum industry.

CONTINUOUS MOLTEN METAL TREATMENTAs larger ingots were made possible by the DC-casting process, quality requirements became more stringent for a wide variety ofproducts. Products that would have been acceptable in the 1940s could not passnew, ultrasonic requirements or produce the surface finish required of polished,chemically treated products. As large 5xxx ingots were hot rolled, lower levelsof sodium and calcium were required to prevent edge cracking. Low hydrogen levelswere needed to prevent blisters in the heat-treated products of other alloys.

Typical early methods consisted of fluxing the furnace with chlorine to removehydrogen, then allowing the inclusions to settle before casting. These methodswere inefficient, ineffective, and environmentally unsound.Those factors drovethe need for better metal-treatment methods.

Deep-bed filtration (the Alcoa 94 process) used tabular aluminum balls and chatto trap oxide inclusions as the metal flowed from the holding furnace to thecasting pit. The Alcoa 181 process introduced argon into the bed filters to

assist hydrogen removal,17 but avoided the use of chlorine, which could clog thefilters with molten salts. One breakthrough came with the development ofinternally heated bed filters, which allowed the size of the units (and metal

flow rates) to be increased substantially. Also important was the introduction ofthe Alcoa 622 process, which used a spinning nozzle to inject a fine dispersionof argon-chlorine gas bubbles into the molten metalto remove impurities.Theprocess, which used very low percentages of chlorine (1 10%), was successful inreducing emissions while maintaining internal ingot quality.

An important side benefit of in-line metal treatment was the introduction ofcontinuously fed grain refiners. With large filter boxes, titanium-bearing grainrefiners could be fed in-line at the desired rate without settling out in thefurnace. Among the benefits of the continuous-grain-refiner additions werereductions in ingot cracking, more uniform ingot structures, and improved

forgeability. Another advance in metal filtration came with the introduction ofrigid, ceramic foam filters. Those filters allowed the metal to be cleaned justprior to casting and offered an inexpensive, smaller-volume alternative to thelarge, continuous bed filters.

Figure 5. A range of extrudedaluminum used in modern industry:(a-top) microvoid hollowextrusions for heat exchangers(shown in cross-section), (b-bottom) extruded aerospaceshapes.



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Some of the product benefits enabled by new, in-line metal treatments wereimproved fatigue performance of aerospace products, fewer pinholes in thinaluminum foil, fine aluminum wire, sheet that would not fracture during canforming, and higher surface quality in both as-fabricated and machinedconditions. The major processing improvements that resulted from higher-qualityingot were reduced edge cracking and blistering during hot rolling of 5xxx ingot.Today, many new and efficient methods are available for filtration and molten-metal treatment.These commercially available processes are selected based on acombination of cost, molten-metal flow rates, and customer requirements.

ALLOY 6061The first commercial aluminum-magnesium-siliconalloy (51S) was developed and brought to market by

1921.18 The introduction of alloy 61S (6061) in 1935filled the need for medium-strength, heat-treatableproducts with good corrosion resistance that couldbe welded or anodized. Alloy (62S) 6062, a low-chromium version of similar magnesium and silicon,was introduced in 1947 to provide finer grain sizein some cold-worked products. Unlike the harderaluminum-copper alloys, 61S and 62S could be easilyfabricated by extrusion, rolling, or forging. Thesealloysechanical properties were adequate (mid 40-45 ksi range) even with a less-than-optimum quench,enabling them to replace mild steel in many markets.The base composition was a ternary aluminum-magnesium-silicon alloy with small amounts of copperfor strengthening and chromium for recrystallizationcontrol.

Alloy 6061 evolved after its initial developmentuntil, in 1963, the alloy limits were broadened toeffect its combination with alloy 6062. In Europe,alloy 6082 is used more commonly than alloy 6061.Mechanical properties are similar, but, rather thanchromium, manganese is used for recrystallization

control.

The corrosion resistance of alloy 6061 even afterwelding made it popular in early railroad and marineapplications, and it is still used for a variety ofproducts. The ease of hot working and low quenchsensitivity are advantages in forged automotive andtruck wheels (Figures 6a and 6b.) Also made fromalloy 6061 are structural sheet and tooling plate

produced for the flat-rolled products market, extruded structural shapes, rod andbar, tubing, and automotive drive shafts.

ELECTRICAL CONDUCTORS

Figure 6. Typical forged (a-top)automotive wheels and (b-bottom)truck wheels produced from alloy6061 for the transportationmarket.



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The electrification of the United States just after the turn of the century cameat an ideal time for the aluminum industry to develop its first significantlarge-volume market. As smelter production increased and aluminum pricedecreased, its competitive position versus copper improved. At the same time,electrical-conductor cable became a viable product, with J.W. Hoopes

investigating ways to produce the new product in 1902. 19 After abandoning the

extrusion process, Hoopes developed alloys with sufficient conductivity but lowstrength. He solved the strength problem by reinforcing the soft aluminum wirewith steel. This aluminum conductor steel-reinforced (ACSR) wire outperformedcopper at a lower cost and withstood extremes in temperature. A patent for theproduct was granted in 1908 and by 1929, 482,803 km of aluminum conductor spanned

the United States.20

The development of the high-volume ACSR product was a critical technicalmilestone.19 Because of competition in this market, the aluminum product wassubject to continuous improvement in its conductivity and consistency. Hoopes andothers went on to develop processes to refine aluminum to 99.99% purity. Testing

methods and quality-assurance procedures were put into place to guarantee thatthe product would provide consistent electrical and structural performance. Laterrefinements to electrical conductor alloys have resulted in higher strengthlevels without significant losses in conductivity.

CONTINUOUS CASTINGThe development of continuous casters for aluminum products has been welldocumented over the past 50 years. While patents for continuous casters date backto the 19th century, the first commercial application of continuous casters can

be attributed to Properzi.21 The wheel/belt caster was used to produce low-costelectrical-onductor wire in 1948. One of the first slab casters, introduced byRigamonti in the early 1950s, cast narrow strip, roughly 100 mm by 20 mm thick.Other casters developed during the 1950s by Pechiney, Alcan, and Hunter Douglaswere also limited to narrow widths (250 mm) and produced small-volume nicheproducts. One notable high-volume application where width did not matter wasCoors use of the process to produce stock for impact-extrusion slugs for itsfirst generation of aluminum cans. Narrow casters of this type are still widelyused today for making impact-extrusion stock.

The most important developments in aluminum casters, though, were those that

enabled the manufacture of wider products. That capability made continuous-casterprocesses competitive with hot mills for foil and some common alloy products.Hazelett developed a twin-belt casting process that used mild steel belts andfast film water cooling to make a slab which was continuously hot rolled to coil.

One of the first successful Hazelett casters was installed by Alcan in 1959.22

A modified Hazelett caster at Alcan Arvida works in Canada began producingreroll coil from 1xxx, 3xxx, and 8xxx alloys in 1971. In 1981, the Hazelett unitwas replaced by a wider, twin-belt machine designed by Alcan.

The Hunter twin-roll caster, developed in the 1940s and commercialized in theearly 1950s, produces strip from two water-cooled steel rolls. Roll cast strip istypically 5 10 mm thick and continuous improvement by Fata-Hunter, SCAL(Pechiney) and others has resulted in commercial widths of more than 2,100 mm.



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Twin-roll casters are, by volume, the largest producers of continuously-castaluminum flat-rolled products, with more than 260 casters in productionworldwide. A typical roll caster in operation is shown in Figure 7.

Continuous casters have greatly changed thelandscape of the U.S. flat-rolled products industryby avoiding the high capital costs of conventionalingot/hot rolling facilities. The elimination of DCcasting, scalping, and much of the breakdownrolling costs typically lowers operating costssignificantly. In North America, nearly 25% of U.S.sheet and foil volume is produced by either roll orslab casters. The primary markets for continuous-cast sheet have been building products, householdfoil, fin stock, and formed containers. When hot-mill sources are not available or surfacerequirements are not as stringent, it has been used

successfully for sheet products such aslithographic sheet. To date, the use of continuous-cast products has been mostlylimited to low-solute alloys (typically 2.5% magnesium or less). Slab castershave produced some higher magnesium alloy sheet for tab or coated lid stock forbeverage containers.

Similar economies are seen where continuous casters have replaced the extrusionprocess. Redraw rod for making wire ranging from nails to screen wire is producedfrom bar casters similar to those developed originally by Properzi. Electrical-conductor wire is manufactured almost entirely with continuous-cast production,enabling larger and more consistent coils to be supplied to the customer. Alloys

produced on bar casters range from the electrical-conductor grade 1xxx series tohigher-solute alloys such as 5154 and 6061.

A more detailed review of equipment development and process parameters for abroad range of the early continuous casters is given in Reference 23.

SHAPE-CASTING ALLOY A356The sheer volume of aluminum shape castings used in the industry over the yearsmakes the development of alloys with good fluid-flow characteristics and usefulmechanical properties after heat treatment one of the most important innovationsof the aluminum industry. By 1921, Archer and Jeffries had developed alloy 195, a

heat-treatable sand-casting alloy suitable for a variety of uses.24 Many of thefirst applications for castings were for architectural spandrels used in buildingconstruction. One of the notable applications of castings produced at AlcoaCleveland works was for the exterior of the Empire State Building. Aluminum castpistons and aircraft engine blocks quickly came into use in the early 1920s. In1928, the 11,340 tonnes of heat-treated cast products also included washing-machine agitators, vacuum-cleaner bodies, and food-processing equipment.

The early casting alloys were based on achieving a given level of heat-treated

strength. A significant cast alloy improvement was the introduction of alloyA356. Lemon, Hunsicker, and coworkers25 reduced iron content to free more copperfor precipitation hardening and reduce insoluble constituent particle content.The cleaner microstructure improved ductility, corrosion resistance, and other

Figure 7. Continuously-cast stripexiting a twin roll caster.



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secondary properties, opening up a number of new structural markets for aluminum-cast products.

Today, more than 90 different compositions are registered by the Aluminum

Association for the production of aluminum castings.26 These alloys are tailoredto the end-use properties, economics, and casting method. While many of the cast

alloys are an important use for secondary (recycled) aluminum, some of the alloysrequire high levels of pure metal to achieve the desired product requirements.Die, permanent mold, and sand castings make up the vast majority of caststructural applications. Engines, transmissions, and cast wheels dominate the

tonnage of castings used for light vehicles.27

EXTRUSION PRESS QUENCHINGFacing competition from wood and plastic for the building-products market, theneed for an inexpensive aluminum product was paramount. Today largest market

for aluminum extrusions is in the building and construction market, where in1999, U.S. production was almost 635,029 tonnes.28 The marriage of market need,alloy, and process was critical for making aluminum extrusions successful in thismarket. Low extrusion pressures for soft 6xxx alloys make them ideal for complexshapes and hollows, which helps simplify customer joining and assembly. Thepress-quenching process eliminates the need for a separate solution heat-treatment step and is critical to making a low-cost product with reasonablestrength.

Press quenching at Alcoa had a thoroughly pragmatic origin in the early 1930s,unrelated to the building-products business. When it was necessary to make alloy

2117 extrusions that werelonger than existing heat-treatment furnaces, hand-heldhoses were used to water-quench the extrusions on the runout table. 29 At aboutthis same time, alloy 6053-T5 was introduced, meeting mechanical property limitsby cooling in ambient air on the runout table. As customers required larger-diameter products from this alloy, it was discovered that forced-air cooling onthe table was necessary to achieve the desired strength levels for the T5 temper.Alloy 6063 was introduced in 1944 for extruded products. Because it was a heat-treatable, low-solute aluminum-magnesium-silicon alloy, it could be extruded athigh rates, yet age-harden to adequate strengths. In addition, the alloy could beanodized and colored easily, and the corrosion resistance was superior to that ofalloy 6061. The low quench sensitivity of alloy 6063 insured press heat treatmentwith moderate cooling rates, enabling complex sections to be produced withminimal quench distortion.

Today market needs for extruded building and transportation products are met bya variety of alloys and processing methods. Alloy 6463, with low iron, issuitable for applications where a bright, anodized finish is required. An evenlower solute (and higher productivity) alloy 6060 is used where the strength ofalloy 6063-T5 is not needed. Extrusions may be quenched by air, mist, sprays,standing wave, or quench tank, depending upon the geometry and final productneeds. Low-copper 7xxx alloys are also commonly press quenched for a variety of

applications ranging from bridge decks to automotive bumpers.30 These alloysinclude 7005, 7003, and 7108.



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CONCLUSIONWhat conclusions and lessons for the future can we draw from the last 100 yearsof successful product and process developments?

The market will drive the selection of alloy, process, and product form to

the low-cost, functional alternative. Economic considerations will beparamount as aluminum products defend their territory or go after newmarkets against competitive materials. To this end, lower-cost metal units(recycling) and process alternatives will continue to be pursued.

For markets where material cost is not the primary driver, alloys andprocessing methods will likely become even more highly specialized. Uniquecombinations of product properties and attributes will be necessary forhigh-performance, likely low volume, applications.

Understanding the real functional advantages and limits that an aluminumproduct brings to the end customer will be essential for future innovation.A product solution can be successful by saving the customer assembly costs

or providing lower operating-life-cycle costs. Low density and product versatility have been keys thus far in expandingaluminum fast-growing transportation market. Future developments shouldexploit new design, joining, and finishing methods to combine the attributesof various mill products to meet the needs of the customer.

ACKNOWLEDGEMENTSThe author thanks the manyAlcoaemployees, present and retired, who contributedto this historical perspective either by direct conversation or by carefully

describing their research in internal or external reports. A particular gratitudeto a number of retired Alcoa employees whose service dates reach back as far as1937: Harold Hunsicker, John Hatch, John Jacoby, James T. Staley, and RonaldBachowski. Excellent detailed accounts of much of this history are found inReferences4, 16, and19.

References1. Aluminum Statistical Review for 1999 (Washington, D.C.: The AluminumAssociation, Inc., 2000).

2. C.C. Carr, Alcoa, An American Enterprise (New York: Rinehart and Company,Inc., 1952).3. W.T. Ennor, U.S. patent 2,301,027 (1942).4. J.D. Edwards, F.C. Frary, and Z. Jeffries, The Aluminum Industry, Vol. 2 (NewYork: McGraw-Hill, 1930).5. Harold Y. Hunsicker, Alcoa Technical Center (retired), personal communication.6. Z. Jeffries, wo Decades of Precipitation Hardening Alloys, Metals anAlloys, 1 (1) (1929), pp. 3 5.7. H.Y. Hunsicker and H.C. Stumpf, History of Precipitation Hardening, SorbyCentennial Symposium on the History of Metallurgy (New York: Gordon and BreachScience Publishers, 1965).

8. J.D. Edwards, F.C. Frary, and Z. Jeffries, in Ref. 4, p. 234.9. Harold Y. Hunsicker, Alcoa Technical Center (retired), personal communication.10. J.T. Staley, J. Liu, and W.H. Hunt, Jr., Advanced Materials and Processes,152, (4) (October 1997), pp. 17 20.



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11. W.F. Hosford and J.L. Duncan, he Aluminum Beverage Can, ScientificAmerican(September 1994), pp. 48 53.12. W.A. Anderson and J.K. McBride, lloy 5182, U.S. patent 3,502,448 (1970).13. E.D. Fraze,U.S. patent 3,273,744 (1966).14. Aluminum Statistical Review for 1999 (Washington, D.C.: The AluminumAssociation, Inc., 2000), p. 14.

15. M.B.W. Graham and B.H. Pruitt, R&D for Industry (New York: CambridgeUniversity Press, 1990), pp. 88 89.16. C.C. Carr, Alcoa, An American Enterprise (New York: Rinehart and Company,1952), p. 183.17. K.J. Brondyke and P.D. Hess, iltering and Fluxing Processes for AluminumAlloys, Transactions AIME(New York: AIME, 1964), p. 1553.18. J.D. Edwards, F.C. Frary, and Z. Jeffries, in Ref. 4, p. 245.19. M. B. W. Graham and B. H. Pruitt, R&D for Industry (New York: CambridgeUniversity Press, 1990), pp. 93 96.20. J.D. Edwards, F.C. Frary, and Z. Jeffries, in Ref. 4, p. 13.21. D.M. Lewis, Metall. Rev., 6 (22) (1961), pp. 143 192.

22. E.F. Emley, Int. Metall. Rev. (206) (June 1976), p. 102.23. Papers presented at the Continuous Casting Seminar (Washington, D.C.:Aluminum Association, 1975).24. Z. Jeffries, wo Decades of Precipitation Hardening Alloys, Metals anAlloys, 1 (1) (1929), p. 4.25.H.Y. Hunsicker and R.C. Lemon U.S. patent 3,161,502 (1964).26. Designations and Chemical Composition Limits for Aluminum Alloys in the Formof Castings and Ingot(Washington, D.C.: Aluminum Association, 1999 February).27. J.C. Benedyk, utomotive Aluminum Casting Trends and Developments, LightMetal Age, 58 (9 10) (October 2000), pp. 36 41.28. Aluminum Statistical Review for 1999 (Washington, D.C.: The Aluminum

Association, 2000), p. 24.29. R. Couchman, Alcoa (retired), unpublished work.30. R.F. Ashton, he Metallurgy of Press Heat Treatable Al-Zn-Mg ExtrusionAlloys (Paper No. 12, presented at the Int. Extrusion Technol. Seminar, NewOrleans, March 3 5, 1969.

Robert E. Sanders, Jr. is withAlcoa, Inc.

For more information, contact R.E. Sanders, Jr., Alcoa Inc., 100 Technical Drive,Alcoa Center, Pennsylvania 15069; (724) 337-2478; fax (724) 337-2044; [email protected] .Copyright held byThe Minerals, Metals & Materials Society, 2001

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