It's more likely that it was poorly welded in the first place - low power machine and no weld prep, then it was ground flat to look nice leaving a tinfoil thick weld to hold it together.
That looks like alloy. If the temper of the alloy is high or the material type 5000 6000 or 7000 series the alloy will work harden and break on the outside of the bend. I have had this happen on 6000 series T6 when in a rolling machine. It will roll bend so far then just snap / tear on the outside of the bend. You can of course weld it back up and then grind it back smooth to hide the fracture
I don't believe it is welded, its been bent with a too tight / sharp bend, it looks like bright bar which doesn't bend too well done cold, I've seen this type of crack many times when cold forming bar, the only thing to do with that now is to weld it up, TIG would be ideal but a 2.5 mma electrode will also get the job done, vee it out a bit before welding to get some penetration.