Effect of heat treatment conditions on stamping deformation and springback of 6061 aluminum alloy sheets

The stamping deformation and springback of the 6061 aluminum alloy sheets under different heat treatment conditions were investigated by three-point bending tests. A validated reliable finite element (FE) model was used to further reveal the springback mechanism. It was found that the heat treatment conditions have great influence on the stamping deformation and springback of 6061 aluminum alloy sheets. The most severe local deformation occurred at the punch position of the T6-8 h alloy sheet, showing minimum bending radius and thickness. However, the bending radius and thickness of the homogenization treated (HT) alloy sheet were maximum, resulting from more materials participate in bending deformation. The HT and solution treated (ST) alloys exhibited higher stamping performance than that of the natural aged (NA) and T6 alloys. The material strength of the T6 alloys can be improved by aging time, motivating greater springback and neutral layer offset. The springback and neutral layer offset of the T6-8 h alloy sheet were the highest, while the HT alloy sheet was the lowest. Furthermore, the effect of material parameters on stamping deformation and springback of sheet was studied by combining with theoretical analysis and experimental results. The research showed that the bending radius and thickness of the sheet in the fillet region increase with the increase of strain-hardening exponent and elongation and with the decrease of yield ratio. After unloading, springback angle and radius increase with the increase of yield strength and strength factor and with the decrease of strain-hardening exponent. These achievements may serve as a guideline for enhancing stamping performance and reducing springback of the aluminum alloy sheet in bending process.