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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 | N O V E M B E R / D E C E M B E R 2 0 1 8 1 5 1980 Lincoln Versailles featuring an aluminum hood. car companies with scrap-incompat- ible alloys. Ford pursued a uni-alloy approach using 2036 for both inners and outers. After trying Alcoa’s 5020 alloy, General Motors had settled on 2036-T4 for skins. But they were strug- gling to make the more complex inner panels such as decklids and turned to 5085, the best forming alloy on the market at the time, developed specif- ically for the auto body sheet market. Introduced in 1972, 5085 was a high Mg alloy with excellent formability in- tended for difficult parts. However, with 6.2% Mg, 5085 proved too costly and difficult for Alcoa to produce and was retired in 1977. Alcoa replaced it with 5182. Unfortunately, the market was now moving toward an incompatible mix of 2xxx and 5xxx alloys. At the 1977 SAE Congress, Eissing- er et al. summarized Ford’s efforts on developing aluminum sheet and noted in their introduction, “… the valuable scrap would have to be carefully sepa- rated from that of steel parts. The over- riding factor to all of this is cost” [2] . The battle for cost had three fronts. The first was a forceful pushback against any solution that would involve a materi- al cost increase. Therefore, the new al- loy would have to follow an economical production path and if different alloys were offered for outer and inner panels, they needed to be scrap compatible. The second was to focus on delivering the lowest part weight. The most direct solution was to use the thinnest gaug- es possible. To do that and still offer the same function meant delivering the highest possible strength on the fin- ished part. However, accommodating thinner gauges meant deepening the beam sections of the hood inner. Un- fortunately, both higher strengths and deeper sections created more difficul- ties for the stampers. And so, the third front was a frantic search to improve formability. The starting point for Alcoa’s next generation of body sheet alloys was 6151, whose strengthening response to the E-coat paint bake cycle had fig- ured prominently in their earlier com- parative testing [3] . They wanted an alloy with a significantly lower yield strength in T4 temper and all of the formabili- ty advantages associated with it, but one that could still achieve respect- able strength after paint. Because such a strong response was not found in 2xxx alloys, Alcoa’s researchers looked for ways to boost 6151’s low formabili- ty. To further improve their chances of success, they settled on a two-pronged approach: One alloy aimed to match 2036’s formability but with much high- er strength after paint, while the oth- er had formability closer to 5182 and strength similar to 2036 after paint. Cru- cially, they would be scrap-compatible with each other. Their approach was to keep enough excess Si to provide the hardening response, plus eliminate Cr and reduce Fe to improve formability. They differentiated between the two al- loys by adjusting the Si and Mg levels, tuning either for strength or formability. B oth Alcoa and Reynolds Metals Company (RMC) approached the automotive market by developing specific auto body sheet alloys, based on their best understanding of these new customers. Corporate strategies were competitive and there was no co- ordination within the aluminum indus- try to define a common approach to the challenges involved. The same scenar- io applied to the automakers, with each company intent on developing a compet- itive advantage. It was natural that the aluminum suppliers would offer propri- etary alloys andoften charged royalties to competitors who wanted to be a second supplier of their patented alloy. RMC’s of- fering, 2036-T4, had become the market leader, while Alcoa’s 5020 and 5085 had not fared well, necessitating develop- ment of a second generation of alloys. In a paper presented at the 1975 SAE Congress in Detroit, Alcoa’s Co- chran et al. made note of the positive impact of recycling aluminum on the overall life cycle equation of vehicles [1] . However, unlike the burgeoning alumi- num beverage can, the life cycle of a car is measured in years, not weeks. The industry could not depend on end-of- life recycling to subsidize aluminum’s greater material and energy costs. Even so, almost half of the auto body sheet sold is made available for recy- cling right away in the form of stamping scrap generated as parts are stamped and trimmed. The realization that aluminum scrap is easily worth eight times more than steel scrap made the separation of aluminum from steel low-hanging fruit for the stamping plants. For alumi- num, the successful recovery and resale of stamping scrap offers an immediate material cost reduction that can exceed 15%. However, mixing incompatible al- loys quickly cuts that value in half. With low production volumes of aluminum parts at that time, the simplest solution was to avoid incompatible alloy com- binations. Unfortunately, that’s exactly what had happened. SCRAP INCOMPATIBILITY In their competitive push to mar- ket, Alcoa and RMC had presented the