Welding Birmabright Alloy. Series Land Rover body panels were made of the Birmabright alloy from the first Series I Land Rovers in 1948 to 1980 then the Birmabright works was shut down. It is not strengthened by heat treatment instead becoming stronger due to strain hardening or cold mechanical working of the material.
The constituents are 7 magnesium sometimes 1. Birmabright can be MIG and TIG welded using the appropriate aluminium wire and shroud gas. Gas welding of Birmabright is easier than that of pure aluminium and may be carried out autogenously using scraps of the same material as a filler rod.
If you are trying to spot weld it try upsetting the weld first with a punch.
Not sure about miging birmabright. It is a skilful procedure and best practised on scrap samples until the necessary degree of proficiency is acquired. Birmabright is best known as the material used in the body of the Land Rover and other classic British vehicles. The welding process typically alters the base metal and the composition of the filler rod is designed to compensate for that effect to result in the strongest weld possible.