PNNL

Abstract

The use of Aluminum 7075 in automobile structural applications is limited by factors such as its limited room-temperature formability in peak-aged condition (T6 temper) and the need for off-line artificial aging to regain high strength if it is formed in soft temper. In this study, two temper conditions have been established that enable 7075 blanks to be stamped at room temperature to create side impact beams that achieve T6 or near-T6 strength without the need of post-forming heat-treatment. The tempering process was conducted at ambient temperatures after solution heat treatment with no additional high temperature aging process after stamping. Both temper conditions on Aluminum 7075 enabled room temperature stamping of the beams with no fractures which showed good formability during stamping. The hardness was measured for both naturally aged alloys where the hardness levels in the lowest deformation regions were within 88% of a conventional T6 aged 7075 alloy. Paint baking of the tempered 7075 beam caused an over aging effect on the beam lowering its strength and ductility. Finite element three point bending simulations of both tempered Al 7075 and baseline boron steel beams showed an equivalent bending force before failure showing good promise for 7075 replacing steel beams in this application which would provide a weight savings of 38%. This study shows successful stamping of Aluminum 7075 alloys at room temperature after just low temperature tempering while having comparable strength to the 7075-T6 condition and equivalent bending force to boron steel beams.