Processing, Mechanical Properties and Elevated Temperature Formability of Automotive AA6xxx and AA7xxx Sheet Materials with High Recycle Content

Abstract

In modern society, car manufactures are actively pursuing vehicle light weighting under both stricter government regulations due to environmental concerns and consumers’ demand for better fuel economy. Under such circumstances, OEMs are using more parts using aluminum alloys to replace parts made with steel. New forming processes are being developed to produce structural components to achieve higher in-service strength using higher strength aluminum alloys. Two of the commonly used high strength aluminum alloys, AA6111 and AA7075, are being considered for elevated temperature sheet forming applications. With more aluminum applications in vehicle and good recyclability of aluminum components, there is a concern of contamination from transition metals such as Fe, Mn and Cr from vehicle end of life scraps getting into aluminum scrap stream. Such impurity elements can have profound impact on aluminum alloy’s mechanical properties, performance and formability at room and elevated temperatures. This study is focused on variants of AA6111 and AA7075 alloys with increased recycling content, and thus higher amounts of the above transition metals. The objective is to investigate the effect of impurity alloying elements on final microstructure, mechanical properties and formability of the above sheet materials. Formability is studied in terms of sheet bendability and elevated temperature forming limit diagrams (FLDs) using a hot gas bulge tester.