Experimental Evaluation of the Quench Rate of AA7075 2014-01-0984

The aluminum alloy 7075-T6 has the potential to be used for structural automotive body components as an alternative to boron steel. Although this alloy shows poor formability at room temperature, it has been demonstrated that hot stamping is a feasible sheet metal process that can be used to overcome the forming issues. Hot stamping is an elevated temperature forming operation in which a hot blank is formed and quenched within a stamping die. Attaining a high quench rate is a critical step of the hot stamping process and corresponds to maximum strength and corrosion resistance. This work looks at measuring the quench rate of AA7075-T6 by way of three different approaches: water, a water-cooled plate, and a bead die. The water-cooled plate and the bead die are laboratory-scale experimental setups designed to replicate the hot stamping/die quenching process. The results verify that water is the most superior form of quenching, i.e. above 1000°C/s, the bead die quench rate is impressive at 525°C/s, and the water-cooled plate quench rate is marginal at 34°C/s. Consequently, the results also indicate a strong correlation between quench rate and final yield strength properties.