Just to start with, for a few years now, off the top of my head most use Carbon Fiber on the Pro Tour, I meen pretty much all. I caught a very few glimses of written words indicating that a few bikes own by a team or two were composites.
These bikes were essentially aluminum alloys containing scandium, perhaps with CF stays, not sure (CF stayed frames, not scand.= compostite) I did not spot them as I was watching it on TV mind you nor can I say how many years ago it was that CF has NOT represented the vast majority of the Pro bikes.
It wasn't like an on 'n' off switch, through the '90s and beyond more and more teams went to CF. It WAS quite drastic of a change square at about '90. Prior to the very few bikes were not "steel". Even in '91 ('90) bikes that were CF were masked to resemble steel but moreso on account of brand sponser interests. Indurain came to make no secret of riding CF after winning the first or second tour.
Titanium wasn't used to my knowlegde and I've no idea to what extent AL. was.