"Vello" wrote:

Thank you all for making things clear! One more strange thing: russians have
a lot of titanium, they even built submarine hulls from that - strange
airframe builders in SU find so little use for titanium. Do anybody know the
reason?

Yes, the earlier varieties of Ti were extremely difficult to
handle and work. Minor contamination with Chlorinated solvents can
lead to rapid and catastrophic corrosion, for example. Many
specialized techniques had to be developed by Lockheed (and presumably
were similarly developed later for the Alfa subs), before Titanium
fabrication could be used for so much of the aircraft.