Effects Of Mn On The Microstructure And Properties Of Biomedical Ti-(Mo,Nb,Ta) Alloys

In biomedical materials,TC4,Ti-6Al-7Nb and other biomedical titanium alloys are applied most widely.But Al,V and other toxic elements contacting with human body fluid in the long term cause secondary damage to human body.The elastic modulus of these alloys is larger,which causes stress shielding with human bone tissue interactions.So the low modulus,non-toxic ? phase titanium alloys become the main direction of research in recent years.Ti-Mo?Ti-Nb ? Ti-Ta alloys have excellent biocompatibility,super elasticity and shape memory property,and have a great application potential for biological material.In the paper,the effects of Mn elements on the microstructure,mechanical properties and corrosion resistance properties of Ti-(Mo,Nb,Ta)alloys were systematically researched,the influence mechanism was discussed,which provides theoretical and experimental basis for obtaining biomedical Ti-(Mo,Nb,Ta)-Mn alloys with excellent comprehensive properties by alloying.The main results of the research are as follows:Ti-8Mo alloy is mainly composed of tiny needles ?" martensite phase.With the increase of Mn content,the ?" martensite gradually disappear and ? phase increase.When the amount of Mn is 1wt.%,? phase is almost retained at room temperature.But? phase appeared in Ti-8Mo-1Mn alloy.When the amount of Mn is added to 3wt.%,? phase is retained at room temperature.For Ti-8Mo-1Mn alloy,stress induced ?-?" martensite transformation occurred,and the phenomenon of "double yield" appeared,and with the increase of Mn content,a single yield appeared.The plasticity of the alloys increases after adding a small amount of 1wt.%Mn.When the Mn content is 7wt.%,the yield strength and tensile strength of the alloy are the largest.The microhardnesses of alloys with Mn are higher than that of the alloy without Mn.The elastic modulus of Ti-8Mo-1Mn alloy containing ? phase is the highest.The elastic modulus of the other alloys containing Mn is 76-87 Gpa,close to that of human bone.In Green solution,the corrosion tendency of Ti-8Mo-7Mn is the least,Ti-8Mo-3Mn is the most easily passivated,forms the passive film and easily is changed from the active state to the passive state.Ti-24 Nb alloy is composed of ? " + ? phases.With the increase of Mn amount,the ?" martensite disappears and the ? phase is retained at room temperature.The Ti-24Nb-1Mn alloy has the best plasticity and strength,and the "double yield" phenomenon appears in the drawing process.The microhardness of all alloys with Mn is high and the microhardness of Ti-24Nb-1Mn alloy is the highest,354 HV.The elastic modulus of Ti-24Nb-3Mn alloy is the highest,up to 167 GPa.The elastic moduluses of the other alloys containing Mn are 78-85 Gpa,close to that of human bone.In the Green solution,the corrosion tendency of Ti-24 Nb alloy is maximum,that of Ti-24Nb-5Mn alloy is minimum,passivation is the fastest,the passive film stability is the highest,most easily changes from an active state into passivation state,the corrosion resistance is the best;while the passivation range of Ti-24Nb-3Mn alloy is maximum.The corrosion resistance of binary Ti-24 Nb alloy without Mn is the worst in all alloys studied.Ti-20 Ta alloy is composed of tiny needles ? " martensite phase.With the increase of Mn content,it gradually evolves into a double phase structure composed of ?" and ? phases.When the amount of Mn is 7wt.%,the alloy is composed of a single ? phase.The tensile strength and microhardness of Ti-Ta-Mn alloys are increased with the increase of Mn content,the tensile strength and microhardness of Ti-20Ta-7Mn alloy are the highest.The elastic modulus of all the alloys containing Mn is larger than that of Ti-20 Ta.The addition of Mn can increase the elastic modulus of the alloys.In the Green solution,the corrosion tendency of Ti-20Ta-1Mn is the smallest and it most easily changes from the activation state to the passive state,and the corrosion tendency of Ti-20Ta-1Mn and Ti-20Ta-3Mn is less than TC4.Ti-20Ta-0Mn alloy has the lowest density and the lowest corrosion rate.The potential width in the primary passivation state of Ti-20Ta-1Mn alloy is maximum and the transition from passive state to active state is more difficult than other alloys.