| In recent years,Ti-Nb alloys have gained substantial attention in aerospace,shipbuilding and biomedical fields due to their high strength,good corrosion resistance and low elastic modulus.However,the mechanical properties of titanium alloys are relatively sensitive to the deformation parameters such as strain rates and temperature,research of mechanical properties under static-dynamic deformation of Ti-Nb alloys can provide a theoretical basis for the processing parameters and product quality.Besides,Ti-Nb alloys may exhibit poor contact friction characteristics in service environment,research of contact friction properties of Ti-Nb alloys are also of great significance for practical application.In this paper,the mechanical properties of Ti-5Nb,Ti-10Nb and Ti-15Nb alloys under static-dynamic deformation were studied,the microarc oxidation coatings were prepared on the surface of the alloys,and the contact mechanical properties of the coating-substrate system were studied.The results of this paper are as follows:(1)The mechanical properties of Ti-5Nb,Ti-10Nb and Ti-15Nb alloys under static-dynamic compression were investigated by SHPB device and Gleeble-3800 thermal mechanical simulator,the effects of temperature,strain rate and Nb content on the mechanical properties of Ti-Nb alloys are studied and the constitutive equations of Ti-Nb alloys at high temperature were constructed.The results show that Ti-Nb alloys belong to a class of metal material which is sensitive to strain rates at high temperatures,the yield stress of Ti-Nb alloys increases with the increase of strain rate and the decrease of temperature.With the increase of Nb content in Ti-Nb alloys,the yield stress has been gradually increased and the plasticity has been gradually decreased.Under high temperature quasi-static compression,the recovery mechanism of Ti-5Nb is mainly dynamic recovery at 800°C,0.001s-1 and dynamic recrystallization under other conditions,the recovery mechanism of Ti-10Nb is mainly dynamic recovery at 760°C,0.001s-1 and dynamic recrystallization under other conditions,the recovery mechanism of Ti-15Nb alloy is mainly dynamic recrystallization.Based on the Arrhenius function,the high temperature flow stress constitutive equations of Ti-5Nb,Ti-10Nb and Ti-15Nb alloys including temperature and strain rate effects are constructed.(2)The contact friction characteristics of Ti-5Nb,Ti-10Nb,and Ti-15Nb alloys were studied by using nano-indenter and ball-disk friction tester,and the effect of Nb content on the contact friction behaviors of Ti-Nb alloys were discussed.The coatings were formed on the surface of Ti-Nb alloys by micro-arc oxidation method,the phase composition and surface morphology of the coatings were characterized,and the contact friction behaviors of the coating-substrate system were studied.The results show that the micro-arc oxidation coatings formed on Ti-Nb alloys are mainly composed of Ti O2,and the content of Nb element has poor effect on the number and size of micropores.The hardness of the substrates increases with the rise of the Nb content in Ti-Nb alloys,but the difference of elastic modulus is small.The hardness and elastic modulus of the micro-arc oxidation coatings are smaller than substrates.The friction coefficient of Ti-Nb substrates increase with the increase of Nb content,and the frictional deformation mechanism is mainly abrasive wear.The friction coefficient of Ti-5Nb and Ti-10Nb coatings is similar to substrates,and the frictional deformation mechanism remains abrasive wear,the anti-friction effect is not obvious.But the friction coefficient of Ti-10Nb coating is significantly lower than substrate,and the frictional deformation mechanism has changed from abrasive to adhesive wear,which provides a good anti-friction effect. |
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