Plastic Flow of AA6013-T6 at Elevated Temperatures and Subsequent Reaging to Regain Full Strength

Combining a retrogression heat treatment with simultaneous warm forming can increase the formability of peak-aged, high-strength aluminum alloys while allowing peak-aged strength to be recovered through a single reaging heat treatment after forming. This process is termed retrogression-forming-and-reaging (RFRA). This study investigates the applicability of RFRA to AA6013-T6 sheet material. Elevated-temperature tensile tests were performed at temperatures from 230 to 250 °C and strain rates from 3.2 × 10−3 to 10−1 s−1. Tensile tests were followed by reaging with a simulated paint-bake heat treatment. Flow stress at a true strain of 0.10 ranges from 230 MPa (250 °C and 3.2 × 10−3 s−1) to 290 MPa (230 °C and 10−1 s−1), significantly lower than the room-temperature yield strength of 360 MPa in the T6 condition. The average elongation to rupture and reduction in area from elevated-temperature tests are 22% and 56%, respectively, which are similar to the room-temperature values for the T4 condition. Elevated-temperature testing reduced material hardness compared to the original T6 condition. Subsequent reaging with a simulated paint-bake raised hardness to 96% of the T6 condition in un-deformed material, but slightly decreased the hardness of the deformed material. Recommendations for implementing RFRA of AA6013-T6 are presented.