Phase Transformations and Mechanical Properties of Two-Component Titanium Alloys after Heat Treatment in the Two-Phase Region (α plus Intermetallic Compound) and High-Pressure Torsion

In this paper, we measure the nanohardness (H) and Young's modulus (E) of three alloys: Ti-2.5 wt % Ni, Ti-2 wt % Cr, and Ti-2.2 wt % Fe preliminarily annealed in the two-phase region of the phase diagram (alpha Ti + intermetallic compound) and then subjected to high-pressure torsion. The titanium alloy with the nickel addition showed the highest H and E values, they vary uniformly from the center to the edge of the sample, and the alloy after high-pressure torsion contains two phases: alpha and omega. The nanohardness of the alloy Ti-2.5 wt % Ni along the sample radius over the surface changes insignificantly: from minimal 4.8 to maximal 5.2 GPa, as does Young's modulus (from 121 to 155 GPa). The maxima of the H and E values fall in the middle of the sample radius. The alloy Ti-2.2 wt % Fe behaves differently: the presence of four phases alpha, beta, omega, and TiFe leads to a strong scatter in the measured H and E values: from 4.4 to 2.0 GPa and from 131 to 12 GPa, respectively. Processing the P-h diagrams allows the nanohardness of the material to be related to its creep behaviour.