MECHANICAL BEHAVIOUR OF Ti-15Mo ALLOY PRODUCED WITH ELECTRON-BEAM COLD HEARTH MELTING DEPENDING ON DEFORMATION RATE AND IN COMPARISON WITH OTHER TITANIUM ALLOYS

Ti-15(wt.%)Mo alloy is produced with conventional cast and wrought approach using double electron-beam cold hearth melting, 3D hot pressing, and subsequent rolling. Three batches of specimens are subjected to microstructure study and quasi-static tensile testing in the following states: (1) as-rolled, (2) partially recrystallized via annealing at 800 degrees C for 40 minutes, (3) annealed at 800 degrees C for 3 hours followed by water quenching to fix the beta-phase. The specimens in the second state (2) are chosen for more detailed study of mechanical behaviour upon both quasi-static and high strain-rate compressions. The obtained data on the mechanical behaviour are analysed from the standpoint of the effect of initial microstructure and crystallographic texture in three mutually perpendicular planes on the strain energy and the critical strain rate that results into fracture. A detailed microstructural study of the tested specimens reveals the influence of microstructure and texture on the deformation mechanisms at different strain rates. A strong effect of microstructural inhomogeneity and crystallographic texture formed during rolling is noted. The results are compared with those obtained earlier for other titanium alloys and some important structural materials tested under the same conditions. As shown, the Ti-15Mo alloy has a rather high mechanical characteristic. At high strain rates, this material corresponds to other single-phase titanium alloys in terms of strain energy; however, it is inferior to the two-phase alloys with a fine and homogeneous microstructure, e.g., Ti-6-4 or T110 (see list of acronyms in Appendix). Taking into account the specific weight of materials, the Ti-15Mo alloy is not inferior to such high-strength materials as the heat-hardened alloy B95, steels ARMOX 600T and Docol 1500M, and, in addition, is cheaper compared to other titanium beta-alloys.