The Properties and Characteristics of Two New Aluminum Automotive Closure Panel Materials 960164
The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing.
The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings. The modified process also lowers the temperature at which a strengthening response is obtained so that this new version of AA6111 can be effectively used with E coat lines operating at 160 to 170°C without compromising the dent resistance obtained today.
The modified production process is also applicable to other 6000 series alloys and has been applied, for example, to the development of a higher formability, reduced springback alloy that gives a paint response similar to today's AA6111 material.
This paper will describe the properties and characteristics of these two new materials and will illustrate their performance in automotive closure panels.