A structure and a method of creating the structure in which relatively thin pieces of non-weldable aluminum alloy or other non-weldable material are welded together. First layers of a weldable material, such as a weldable aluminum alloy or other weldable material, having a total thickness of between 0.01 and 0.30 inches, are built up on a surface of the first piece using an ultrasonic or other solid state joining technique, and second layers of the weldable material having a similar total thickness are built up on a surface of the second piece using the same technique. The first piece is then welded to the second piece at the first and second layers of weldable material using a fusion welding technique. The resulting structure may be part of an aircraft, landcraft, watercraft, or spacecraft type of vehicle or may be used in other high-performance applications.