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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 | S E P T E M B E R 2 0 1 8 1 6 Panhard had a winner on its hands if they could only succeed in getting it into series production. However, by the end of 1954, one year into production, Chausson and Panhard were still strug- gling with unacceptable productivity. Ill-fitting parts and repeatedly fouling weld tips conspired against achieving reliable spot welds, causing repairs and low production yields. Lüders bands on the deeply shaped outer skins showed through paints, so the bodies required signif- icant surface finishing. To make mat- ters worse, the planners at Panhard had made a crucial mistake: Aluminum buying assumptions were based on part weights, not blank weights, so the invoices from Chausson were double what the company had been expecting. It alsomeant that no one had taken into consideration the resale of stamping scrap as an offset for the material cost. Panhard conducted a quick study comparing the weight and cost of the aluminum body to a steel version. The aluminum body weighed 117.5 kg (259 lb), at a cost of French francs (FF) 55,719 (about $159 in 1954 or $1500 today), while a steel equivalent would weigh 239.9 kg (528.9 lb), but cost only FF 15,578 (about $45 in 1954 or $420 today). CITROËN BUYS PANHARD 1954 was also the year of Dien Bien Phu, the French military catastrophe in Indochina, and the company was strug- gling with its military vehicles division, where an expensive contract for the French Army had been slashed. Bank- ruptcy loomed. Panhard first sought an alliance with Ford, but no deal could be worked out. The government in- tervened and prodded Citroën, then owned by tire maker Michelin, to step in. On April 6, 1955, Panhard ceased to exist as an independent company, and its progressive absorption into Citroën started. By September 1955, after two years of production and 25,580 all-alu- minum vehicles, the BIW was converted to steel; the closures would go by the next model year. The 1957 Dyna Z was all steel, lighter than its competitors by virtue of its advanced body engineering and powertrain, but no longer as quick or nimble as it had been. Citroën had come to Panhard’s rescue not out of kindness, but out of cold necessity. Its small model, the iconic 2CV, was France’s best seller and sales were constrained by a lack of capacity. Citroën was simultane- ously in the process of launching the radical replacement for its venerable Traction Avant, itself in production for more than 20 years. The DS is remem- bered for its many radical innovations and avant-garde styling, but few real- ize its significance for aluminum auto body sheet. Citroën had decided on an aluminum hood and decklid, as well as an aluminum or fiberglass roof de- pending on the trim option. The alumi- num decklid remained in production through 1957 and was then replaced by steel. Several other bolt-on parts were also to be stamped in aluminum. They selected Péchiney as the supplier, who offered the same alloy used on the Dyna Z, A-G3. A-G3, like all similar 5xxx alloys, had significant shortcomings. First, it was subject to Lüders bands after stamping, resulting in unacceptable surface quality and heavy metal finish- ing. Second, it had to be delivered in “O” temper to provide the necessary form- ability. As such, it offered only modest strength on the order of 90-100 MPa or roughly two-thirds the strength of mild steel, necessitating serious up-gauging to maintain denting performance. Both problems had beset Panhard since the beginning, but they were a small carmaker and did not hold much sway with metal suppliers. Also, as a 1954 Dyna Z full aluminumbody. Body in whites and closures delivered by Chausson.