Ti-15Mo alloy belongs to metastable β-Ti alloys that are currently used in aircraft manufacturing and Ti15Mo alloy is a perspective candidate for the use in medicine thanks to its biotolerant composition. In this study, Ti15Mo alloy was prepared by advanced techniques of powder metallurgy. The powder of gas atomized Ti-15Mo alloy was subjected to cryogenic milling to achieve ultra-fine grained microstructure within the powder particles. Powder was subsequently compacted using spark plasma sintering (SPS). The effect of cryogenic milling on the microstructure and phase composition of final bulk material after SPS was studied by scanning electron microscopy. Sintering at 750°C was not sufficient for achieving full density in gas atomized powder, while milled material could be successfully sintered at this temperature. Alpha phase particles precipitated during sintering and their size, as well as the size of beta matrix grains, was strongly affected by the sintering temperature.
Metastable beta titanium alloys are perspective materials for use in biomedicine due to their excellent mechanical and physical properties, which can be improved by severe plastic deformation by reducing grain size and inserting a high degree of deformation. Ti-15Mo alloy was subjected to 1-4 passes of equal channel angular pressing in a die with channels intersecting at an angle of 120 • at the temperature of 250 • C. The microstructure observed by means of electron backscatter diffraction showed deformed and highly twinned structure, but the deformation was not sufficient for achieving an ultrafine grained material. The microhardness increased with the increasing number of equal channel angular pressing passes. The Young modulus was measured by the methods of resonant ultrasound spectroscopy and also increased with the number of equal channel angular pressing passes. Significant increment of elastic modulus can be attributed to the formation ω-phase particles.
In this study, Ti-15Mo alloy powder was prepared by gas atomization and subsequent cryogenic milling in order to achieve ultra-fine grained microstructure. Both milled and non-milled powders were compacted by spark plasma sintering (SPS) at temperature of 800 °C for different sintering times up to 6 minutes. Sintering temperature and time affect porosity, microstructure and phase composition of the alloy. Milled powder can be sintered at comparatively lower temperature to achieve fully dense material. Sintering below β-transus temperature results in α+β-structure. Furthermore, amount of α-phase is higher in the material sintered from the milled powder due to increased oxygen content and also due to refined microstructure which facilitates α-phase precipitation. Mechanical properties are also affected by formation of ω-phase during uncontrolled cooling in the SPS machine.
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