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A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 1 9 2 1 develop a continuous joining solution. But this decision had opened another door into the unknown. The concept took full advantage of aluminum’s capabilities, but neither Al- coa nor Audi had prior experience with automotive structural castings or ex- trusions. The metallurgical challenges to produce the needed aluminum parts were considerable, including the fact that structural die castings needed to be highly ductile without brittle fracture in a crash situation. Low Fe content and careful control of the metal treatment and casting processes were essential. The extrusions required by Audi called for high dimensional tolerances before and after forming, as well as ductile crash behavior. Extrusion productiv- ity required a relatively low-Mg alloy, a version of alloy 6060, and control of distortion dictated an air quench. The modified alloy developed by Alcoa met- allurgists was easily extrudable, not embrittled by the air quench, yet could still reach sufficient T6 properties after forming and aging. In the end, the spaceframe was the result of an extensive research and de- velopment effort, supported by 40 pat- ents and seven new alloys. Alcoa built a dedicated plant in Soest, Germany, to support the program and when the first components shipped to Audi’s Neck- arsulm plant, it represented the com- pletion of a 10-year journey. Audi built a dedicated new body shop for the A8, with limited automation and a capa- city of 80 cars per day. Each body in white (BIW) consisted of 334 parts joined by 1100 rivets, 500 spot welds, 178 clinches, and 70 m of metal inert gas welded (MIG) seams, with a total weight of 249 kg. Outer skins used 6016-T4, inner panels 6009-T4, and other difficult-to-form structural parts used 5182-O. Following assembly, each body was heat treated at 210 ° C for 30 minutes before the paint shop. When it went on sale in the sec- ond half of 1994, the A8 asserted Audi’s claim for a seat at the table of the pre- mium German brands. The Audi Space Frame (ASF) succeeded in making the BMW 7 Series and the Mercedes-Benz S-Class appear technically lame. But for Alcoa, it was bittersweet because with- out a production site for 6xxx sheet in Europe, aluminum sheet for the A8’s sleek body shell had been sourced to Alusuisse. Within two years, the A8 had outsold the Dyna Z, its long-ago French ancestor. With its new plant in Soest, Alcoa was now a Tier-1 supplier of body com- ponents and subassemblies, capable of offering value-added products with better margins than those of a raw ma- terial supplier. What’s more, its prod- ucts were part of the body structure, guaranteeing a more stable sales plat- form than supplying sheet for bolt-on components. For Honda and Audi, an aluminum body had been a strategic decision that offered a key marketing advantage with the added benefit that it would be diffi- cult for others to replicate quickly. For both, the aluminum body was a state- ment of technological superiority, Audi 1994 Audi A8. Courtesy of www.wheels.ae . 1991 Acura NSX. Honda NSX body in white.