The invention relates to a method for thermally treating an aluminium workpiece, comprising the steps of providing an aluminium workpiece, which is essentially in the T4 structural state, and exposing a first portion of the workpiece to a first precipitation hardening process by artificial ageing to change the structural state of the first portion of the workpiece, wherein a part of the workpiece is actively cooled during the first precipitation hardening process, so that a second portion of the workpiece essentially remains in the same structural state during the first precipitation hardening process. The invention further relates to an apparatus for thermally treating an aluminium workpiece and to an aluminium workpiece, especially producible with a method according to the invention.