The use of aluminum automobile components is growing steadily from an average of 54 pounds (25 kg) per car in 1960 to 273 pounds (124 kg) in 2002, mainly to reduce weight and improve fuel economy. According to the Drucker Worldwide report, "Global Automotive Content Forecast Through 2010", it is projected that there will be 318 pounds (144 kg) of aluminum used in North American light vehicles by 2010 (Fig. 1).
Heat treatment processes typically require multiple heating and holding steps with intermediate cooling or quenching operations. The soak time at temperature required to achieve the desired properties is a function of alloy's ability to develop a homogeneous solid solution. Soak times can vary from less than a minute for thin sheet to as long as 20 hours for large sand castings.