How To Weld Forged Aluminum. 7020 series can be fusion welded using TIG MIG and oxyfuel processes. The basic steps required are.
Hope this helps as I am not sure what you want to weld. Select a suitable filler I used a 4043 alloy but check with your local supplier what would be best. Clean your aluminum remove any oxide and file the edges that will be joined Avoid pulling while weldinginstead push at a 10 to 15 degree angle Use multiple pass straight beads to improve the overall appearance of the weld and help to avoid defects Use a heat sink which will absorb extra heat and allow you to weld slower.
For welding rods consider MG400 welding rods.
Hope this helps as I am not sure what you want to weld. Most of the wrought grades in the 1xxx 3xxx 5xxx 6xxx and medium strength 7xxx eg. Then bring your piece to the power hammer or a hydraulic press to join the weld. You can join your pieces together with metal wire until the main weld is formed.