I could able to find many heat treatment conditions (T6) in (time duration ranges) for A2219 alloy. But no papers or books mentioning about the optimum T6 conditions for the same alloy anywhere.
For any alloy, heat treatment mainly modifies the grain boundaries and the shape of the eutectic silicon, due to which the properties of the material is altered. In finding an optimum T6 condition first make sure which property you need to improve.