| Titanium and titanium alloy films have great potential in the field of medical implant materials due to their good plasticity,excellent biocompatibility and high corrosion resistance,and are commonly used for surface modification of materials such as stainless steel,titanium alloys and magnesium alloys.In titanium alloy bulk materials,the phase composition of the titanium alloy changes from α to α+β phase and then to β phase as the content of β phase stabilising elements increases,with consequent changes in mechanical properties and corrosion resistance.In titanium alloy thin film materials,the phase composition still has a similar pattern of variation,but the mechanism of the effect of phase composition on mechanical properties and corrosion resistance is not yet clear.Ti-Mo alloy films are one of the more promising thin film materials for biomedical applications,the study of the microstructure and mechanical properties of Ti-Mo thin films and corrosion resistance not only has important theoretical value in revealing the mechanism of the mechanical properties and corrosion resistance of Ti-Mo alloy thin films,but also has extensive reference significance for the organization design and application of other titanium alloy thin film materials.In this paper,a series of Ti/Ti-Mo alloy films of different compositions were prepared by varying the Mo target current using magnetron sputtering technology with high-purity Ti and Mo monolithic targets and sequential deposition of multiple targets,and the effects of Mo content on the microstructure,mechanical properties and corrosion resistance of Ti-Mo alloy films were systematically investigated.The main findings of this paper are as follows:(1)The variation of Mo content on the phase composition of Ti/Ti-Mo alloy films was clarified.The experimental results show that the phase composition of the films changes from a phase→α phase+β phase→β phase with the increase of Mo content:Pure-Ti films have a single α phase;Ti-Mo alloy films have α+β phase when the Mo content is between 7 wt.%and 20 wt.%;When the Mo content is 24 wt.%and above,Ti-Mo films have a single β phase.(2)The variation of Mo content on the mechanical properties of Ti/Ti-Mo alloy films was investigated.With the increase of Mo content,the hardness of the film showed a trend of first increasing and then decreasing:when the Mo content was 7 wt.%～14 wt.%,the hardness of the film was the highest,which was about 7.5 GPa.At this time,the phase composition of the film was α+β phase,and a large number of α/β interfaces were introduced in the microstructure,which produced pegging and blocking effects on dislocation movement and increased the hardness;with the increase of Mo content,the yield strength of the film The yield strength of pure Ti films is about 3100 MPa,the yield strength of films with Mo content of 7-14 wt.%is about 3400 MPa,the proportion of a phase in films with Mo content of 14-28 wt.%decreases,the α/β interface gradually decreases until it disappears,the phase composition gradually changes to a single βphase,and the yield strength is about 2500 MPa.The α/β interface is the key factor affecting the strength of Ti/Ti-Mo alloy films.With the increase of Mo content,the wear resistance of the films first increases and then decreases:the specific wear rate of Ti-14Mo is the smallest,reaching 1.08×10-12m3/Nm,while the specific wear rates of other films do not exceed 2.5×10-12m3/Nm,which is about 1/4 of the specific wear rate of pure Ti bulk materials,indicating that the alloy films have better wear resistance than the bulk materials.(3)The influence of Mo content on the corrosion resistance of Ti/Ti-Mo alloy films was obtained.With the increase of Mo content,the corrosion resistance of Ti-Mo alloy films showed a trend of first decreasing and then increasing,among which Ti-20Mo had the worst corrosion resistance.the corrosion potentials of Ti/Ti-Mo alloy films were all around-0.15V,and the corrosion current densities were all around 1.0×10-6A/cm2,whose corrosion potentials were higher than that of 316L stainless steel,and the corrosion current densities were smaller than that of 316L stainless steel.The impedance arc radius of Ti/Ti-Mo alloy films is 1.27×105～3.26×105Ω/cm2 and the low frequency impedance modulus is 2.13×105～2.94×105Ω/cm2,which is in the same order of magnitude as pure titanium and TC4 bulk,and one order of magnitude higher than 316L stainless steel,The low frequency phase angle of the TC4 bulk is all around 80°,which is more than 10° greater than that of 316L stainless steel.The Ti/Ti-Mo film therefore maintains the corrosion resistance of pure titanium and TC4,which is superior to that of 316L stainless steel. |
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