Formation of the τ Phase during the Deformation in a Quenched Biocompatible Ti–26 at % Nb Alloy: An Effect on Properties

In situ X-ray diffraction studies of a hardened Ti–26 at % Nb alloy with an initial single-phase β structure sublected to tension allows studying the processes occurring upon application of deformation and correlating them to three intervals of strain values. The first range of values (up to 0.7%) is the region of elastic deformation of the bcc lattice of the β titanium solid solution. In the second interval (0.7–1.4%), the occurrence of the strain-induced β → τ transformation is recorded, and, as the strain increases to 1.4%, an increase in the c/a parameter of this lattice is observed. In the third strain range (1.4–2.2%), plastic deformation of the β and τ phases occurs. The resulting τ phase after the test remains quite stable. It is found that after tensile tests, the Young modulus of the hardened Ti–26Nb alloy decreases from 58 to 52–54 GPa, and the microhardness increases from 200 to 240 HV.