Effect of quenching rate on microstructure and mechanical properties of commercial AA7108 aluminium alloy

A commercial AA7108 aluminium alloy subjected to different quenching procedures from the solid solution temperature of 480 degrees C was considered. Both continuously cooling and quenching to intermediate temperatures (400, 300 and 200 degrees C) followed by different holding times were applied. All the materials were subsequently subjected to the same industrial two-step artificial ageing procedure to obtain a maximum strength (T6). Tensile testing of the different quenched materials in the T6 temper reveals a large deviation in strength dependent on the cooling/holding time, compared with the reference sample. A collection of the different quenched materials was chosen for further investigation of the precipitate structure by transmission electron microscopy (TEM) to explain the differences in mechanical properties.