…constructed of some sort of aluminium alloy…
It’s almost certainly made of a precipitation hardened alloy (e.g. 2XXX, 6XXX etc.)
The problem you have is that it will currently be in its hardened state to make it strong. It’s unlikely to be be ductile enough to bend without cracking in this state. Heating (either to bend or through welding) will destroy the hardening and leave the metal little stronger than a wet noodle (I kid you not…).
To restore the strength, it would need to be heat treated – typically a high temperature followed by a quench to get all the alloying elements back into solution, then a lower temperature, longer duration ageing treatment to develop the strength (actually to allow finely dispersed precipitates to form inside the metal). Not impossible to do at home for something of that size, but to be confident, one would need to be pretty sure of the actual alloy it’s made of (also important for selecting the correct weld filler).
At the end of the day, how much do you like your teeth? 😀