Investigation of Quench Sensitivity in 6xxx Aluminum Alloys

Quench trials were performed on AA6005A and AA6016 alloys to assess the sensitivity of their tensile properties as well as bendability to quench after solution heat treatment. Results indicate that the tensile properties in T4 and in the paint-baked state (2% pre-strain + 185 degrees C/20min) are hardly affected by quench rate as long as the exit temperature (T-exit) is sufficiently low. The bendability however, appears to be more sensitive to quench rate, and the sensitivity depends on the chemical composition of the alloy. The alloy with a higher excess Si content exhibits higher sensitivity to natural aging which in turn affects the bending and hemming performance of the material. Therefore, it is not only the quench rate which affects the bendability but also the temperature of the material at the end of quench. DSC analysis revealed how cluster formation proceeding the solution heat-treatment (SH) and quench provokes the quench sensitivity.