Yes you can weld that bracket onto the axle tube.
Lots depends on the heat required to make a proper weld, how clean you can get the area to be welded, welder parts access, visual access.
The welding process will generate enough heat to warp the axle tube if a bead is run too long or too deep, so make preperations for abating the heat as much as possible.
The welding process may cause arcing through the bearings and gears of the rear end if everything is still together.
One way to help with this is to attach the ground as close to the weld bead area as possible, thus limiting the need for the current to pass through other areas of the rear end.
Get the area clean, REAL clean. Basically you can not overclean an area to be welded.
If you wire wheel off the grease and grim it will literally impact some of that grime into the metal, making it almost impossible to get a clean weld bead.
Do not use some cleaning solvents like brake cleaner to clean the area because when you heat the cleaner residue to weld temps it gives off poisionous gasses....no good!
Fit the bracket as nicely as possible to the axle tube for better results too.
This job can be done, and done well. Just take your time, clean things well, don't overheat, and fit things prior to making any sparks and you will probably do nicely.
