The tensile behavior of AA6013 at room temperature and 240 °C

Automotive manufacturers are pursuing technologies, such as lightweighting, that improve vehicle fuel-efficiency and reduce emissions. High-strength aluminum alloys might provide performance equal to the current ultra-high-strength steels while decreasing vehicle weight. High-strength 6xxx-series aluminum alloys, such as AA6013, are candidates for lightweighting structural components of vehicles because of their high strength-to-weight ratios compared to steel. In the peak-aged condition, these alloys often lack the ductility necessary to form complex part geometries at room temperature. Forming at elevated temperatures increases the ductility but can reduce strength. Retrogression forming and reaging (RFRA) is a relatively new technology for warm forming parts in high-strength aluminum alloys and then recovering strength to equal the peak-aged condition. Previous studies on aluminum alloy AA6013 performed by Rader et al. demonstrated a significant response to retrogression and reaging. New data for AA6013 are presented from tension tests at room temperature and 240 °C, an appropriate temperature for retrogression of this alloy. The effects of different heat treatments on room temperature properties are investigated. The effects of temperature and time at temperature on plastic deformation are investigated using experiments at 240 °C. Retrogression from the T6 temper reduced room-temperature strength by 3.5%, but subsequent reaging restored strength to within 2% of the original T6 temper. At 240 °C, the yield stress was 25 to 30% lower and elongations after rupture were 42% higher than at room temperature for the T6 temper. Stress relaxation at 240 °C decreased stress by 32 to 43% at a fixed elongation within approximately three minutes. These results suggest that RFRA could be viable for forming complex components in AA6013-T6