Investigating the quench sensitivity of high strength AA6082 aluminium alloy during the new FAST forming process

Abstract

Optimised manufacturing rates offer enormous cost saving benefits to industry. FAST (Fast light Alloys Stamping Technology) has been recently developed to rapidly and economically manufacture high-strength panel components from sheet metal alloys. For heat treatable aluminium alloys, artificial ageing is subsequently employed to strengthen the formed components. The diffusion-controlled precipitation response is dependent on the cooling rate. The temperature evolution during FAST quenching significantly affects the final strength. In the present research, the AA6082 specimens were heated to the target temperature at an ultra-fast rate and cooled by either air (providing different quenching rates) or water, followed by artificial ageing at 180°C. Hardness measurements were conducted to track the strength evolution of the specimens during thermal cycles. Transmission electron microscopy was also performed to characterise the microstructures under different cooling conditions. Based on the experimental results, quench sensitivity during FAST has been analysed in depth and modelled. This detailed quenching sub-model was incorporated in the post-form strength prediction model, for simulating strength of the components. A great agreement between experimental data and modelled results has been achieved with the deviation less than 7%. By identifying undesirable quenching methods, optimisation of the forming process is thus possible, improving the final strength of the formed parts.