What material is Iron Man's armor made of?

As I recall, a tank knocked Iron Man in the first MCU movie, but he survived (with some black spots on the armor).

AFAIK, Vibranium is in limited supply in the MCU (Captain America's shield). Tony created a new element in Iron Man 2, and that's also in limited supply.

So what material is Iron Man's armor made of? It doesn't look like iron to me.