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Austempered ductile iron (ADI) castings provide a unique combination of high strength and toughness coupled with excellent design flexibility for chassis applications. This paper describes the development of the upper control arm for the 1999 Ford Mustang Cobra as an austempered ductile iron casting. The full service development process used is described from initial design through finite element analysis (FEA), design verification, casting production, heat treatment, nondestructive evaluation and machining. To achieve significant weight savings, an austempered ductile iron casting was chosen for this application instead of an as-cast SAE J4341, Grade D4512 ductile iron casting or a steel forging. This is believed to be the first application of an austempered ductile iron casting for a safety critical, automotive chassis application.

For the new 4.7 L, V-8 engine, which was introduced in the all new 1999 Jeep Grand Cherokee, Chrysler product engineers found they needed a bedplate material that was significantly stronger and stiffer than gray iron to help meet engine weight requirements. The material also had to provide good NVH characteristics, be cost effective, and machinable. Intermet Corporation, the casting supplier, wanted a material that was significantly tougher than gray iron, would cast sound in complex sections, and which could be reliably produced on a cost effective basis. This paper presents an overview of the development, properties, casting practices, and engine validation of enhanced compacted graphite iron, a material specifically developed and tailored for the bedplate of the new 4.7 liter engine.