I guess I ment emt. I have never really considered what material it was, just figured it was aluminum...
Knowing your materials can be pretty important.

but then I have 2 decades of industrial design experience.
Your t-post to emt clamp is pretty cool! But why go through all the effort? Do you think you could have just gone to a 1.5 inch pipe and sank the emt directly? Maybe even go so far as to fill the pipe with sand or concrete? It seems to me like the only difference would be lift resistance from the plate on the t post, but is it needed for your application?
Not quite sure what you mean by this....sink 1.5" EMT as posts and bend for rafters?? Use standard 1.5" EMT couplers to join posts to rafters?
I think that would actually be harder
and more costly.
I could not have bent 1.5" EMT for the rafters, it took about all I had to bend the 3/4",
it was tricky to learn tho, made a few 'bad' ones before I figured it out.
Why's.
I did not want to dig holes for posts. Locating, plumbing, and pounding Tposts to the needed height is
much easier than setting posts in a hole. The plate on the Tposts is more for alignment of fence face sides of post than lift resistance and keeps the post from twisting as you pound it in. I also wanted something that was movable/removable, half the Tposts in the run were taken from an old garden fence project. Using Tposts is pretty easy in my soil, have been using, moving and reusing them for a long time.
The clamps were not that hard to make, cut 2" PVC to length, drill a couple holes using drill press, and done! It did take some time researching then dinking around to find a way to make them work, they started with the screw set idea from some commercial Tposts clamps.