Aluminium use in car parts

[Sam-Q]

these guides and tips for welding 4130 are only to gain maximum theoretical strength. Parts welded normally and left that way are still very strong and can usually be trusted. I happen to know of a bicycle maker who doesn't post heat treat their frames and I have never heard of them having an issue.

[GT-R Glenn]

How many tig, d crmo rollcages have you seen that have been heat treated ? ,
I you want to fab bottom arms or any suspension parts like that use crmo tube , it is cheapenough when you only need a small amount , if you want to be really fussy you can heat tthe welded area to a dull cherry red and let cool naturally, but its overkill if its welded by a good fabricator / welder.
The problem with ally is there are so many different types and hardnesses you might as well go straight to crmo and no for sure its fit for purpose.

Or, what are all fabricated a arms made from ?