2024 is a precipitation-hardening alloy, with the main alloying ingredient being copper (4% or so, but I'm working from memory on that one). The strength comes by forming submicroscopic precipitates of the Cu-Al intermetallic; strength increases as these particles grow. The local straining gives the properly-treated alloy its strength. If they grow too large, they lose coherency with the surrounding aluminum and the strength decreases rapidly.
So--you must first dissolve the copper completely by holding at a high temperature for awhile; this is called solution treating. Then hold at a lower temperature, where the Cu-Al starts to precipitate. (A rough analogy: fog or rain forms when temperature drops below dew point). This is called precipitation hardening. But don't hold it too long, because it will then lose strength when the particles grow too large (called over-aging).
It is very empirical. A heat-treat shop will know exactly what temperature and time will give maximum strength. (The designations T3, T6, etc. refer to specific temperatures, times, and strengthening mechanisms that result).
Sorry for the long-winded discussion. It dredges up memories from a previous life and career, before I started disappearing frequently to go fly when dispatch called.