Orientation Relationships and Changes in the Composition of S2 Titanium Silicides in Titanium Pseudo-β-Alloy VT47

The orientation relationships between the β-phase and the S2 silicides (Ti, Zr)₆Si₃ (a = 0.7055 nm, c = 0.3673 nm) in titanium pseudo-β-alloy VT47 are studied. The distribution of the crystallographic directions on an inverse pole figure in the β-phase coordinates is presented. A large sample of silicides is studied, and absence of single orientation relationships between the β-phase and the S2 silicides in the alloy after rolling and annealing is inferred. Variants of nucleation of S2 silicides are considered on the basis of the theory of nucleation and of data on the Ti – Zr – Si system. Amechanism of the loss of β/S2 orientation relationships in the process of thermomechanical treatment of the alloy is suggested. The Ti/Zr proportion at a constant content of Si is shown to grow with the sizes of the silicides. The silicide particles affect the initial aging state of alloy VT47. They serve free surfaces for nucleation and growth of β-phase during aging and make its distribution more uniform.