Dedicated to Akademik Professor N.N. Sirofn on thc occasion of his 75 th birthdayThe overall deformation behaviour between room temperature and 1000 K has been investigated by bending and uniaxial compression at small strains 5 0.1%. Ductile-tobrittle transition temperature was found at 44% of the melting point. Dislocations are generated mainly at surface irregularities. Whereas screw dislocations predominate a t the beginning 30" and 60" segments become more important after cross slip and interaction of different slip systems.