Pretty much EVERYTHING is ALUMINUM nowadays. If you drive a car newer than the 90s then there is a good chance parts of your engine is ALUMINUM and there is a LOT of ALUMINUM flying over your head everyday because I don't think they EVER made AIRPLANES out of much steel . About the only parts that are steel are the inner barrels of the shock struts and the actuating cylinders.
Crotchrocket frames are Aluminum for weight to HP ratio. The lighter it is the less inertia it takes to move it. A properly welded and heat treated aluminum M/C frame is as strong if not stronger than the OLD school bike frames. The older M/C frames are made from very THIN walled tubing and are not actually that strong compared to a new Sportbike frame made of ALUMINUM!!
Xnavylfr(CHUCK)
So when you spend $30,000 dollars for a state of the art Ducati, what is the frame made from? ....Steel tubing.
Yes you can make aluminum frames for motorcycles, but they will be throw away frames. If they get damaged they will have to be thrown away.
There are no airplane parts welded together except for very small parts. There are very few of those parts. I was a jet engine mechanic in the USAF.
The American Welding Society have articles in Welding Journal Magazine where tests were performed on 12 foot sections welded together for airplanes and they were not successful.
The idea was to eliminate all of the rivets in the airplane.
Instead the new 787 dreamliner uses a lot of carbon fiber parts riveted together.
But guess what happened. The rivets (special design) were installed in the first 3 planes by young men with not much experience and all three of the first test planes had to have 3,000 rivets replaced. You can go online and read about that.
Rivets in aluminum holding carbon fiber sections caused the carbon fiber to crack.