High Temperature Deformation Behavior And Microstructure And Properties Of Biomedical Beta Ti-12Mo-3Nb-1.5Cu Alloy

The titanium alloys are widely used in biomedical implants due to its comprehensive mechanical properties and biocompatibility.However,the bacterial adhesion and proliferation on the surfaces of traditional biomedical titanium alloys with poor antibacterial performance are likely cause bacterial infection and failure of surgery,and bacteria are easily attached to their surfaces,causing infections.So the development of a new type of titanium alloy with antibacterial capacity has become the current hot spots.In this paper,the?-type titanium Ti-12Mo-3Nb-1.5Cu alloy was prepared as research object,with the adjunction of Cu element because of its excellent antibacterial properties,the use of a long time and low cost advantages.The result shows that microstructure of as-cast Ti-12Mo-3Nb-1.5Cu alloy is?phase grain.The hot compression test was conducted under the 800°C⁹00°C of temperature and 0.01s^-11s^-1of strain rate.The results of hot compression test show that the peak flow stress of Ti-12Mo-3Nb-1.5Cu alloy is sensitive with the deformation parameters:negatively related to the deformation temperature,and positively related to the deformation rate.The thermal activation energy of Ti-12Mo-3Nb-1.5Cu alloy is 259.280KJ/mol.The dynamic recrystallization level of the alloy increases with the deformation temperature,and decreases with the deformation strain rate.The discontinuous dynamic recrystallization mechanism of Ti-12Mo-3Nb-1.5Cu alloy is as follows:with the inhomogeneity of deformation between grains,the grain boundary lead to form the "bent bow.",then strain-induced subgrain boundary changes from small angle to large angle grain boundary,and the protrusion of grain boundary is directly nucleated to form new.According to the experimental results of single and multi-pass thermal deformation simulation,the optimal parameters of plate rolling were determined.The microstructure and mechanical properties of the alloy plate were tested.The results show that the microstructure of the alloy plate after rolling is equiaxed?-stable grains with a large number of small-angle grain boundaries inside the grains.After the solution treatment at 900°C,the microstructure changes to dislocation-free?grains.The tensile test shows that the original plate has higher strength?1206.09MPa?and higher elastic modulus?80.55 GPa?but lower plasticity?elongation6.24%?;the sheet after solution treatment has a lower strength?854.60 MPa?,lower elastic modulus?68.63 GPa?but higher elongation of 35.56%.Tensile fracture shows that the fracture mechanism of the alloy original plate is a mixed fracture with high strength;while the plate after solution treatment is ductile fracture,there are a large number of dimples on the fracture,the plasticity is better but the fracture strength is lower.The results of the heat treatment of the alloy show that the precipitates of primary?phase after solution treatment in the two-phase region at 750°C,and the primary?phase disappears with the solution temperature rises to single-phase region.On the other hand,after the aging treatment at 500°C for 8h,the alloy will precipitate a needle-shaped secondary?phase.The microhardness of the alloy has microstructure sensitivity:the microhardness of the alloy after solution increases first and then decreases as the temperature increases,and the alloy after aging further increased to 496.8 HV due to the precipitation of secondary?phase.After solid solution in the two-phase region,the distribution of Cu is manily enriched in the?phases while depleted in primary?.After aging treatment at 500°C,eutectoid reaction occured:??Ti₂Cu+??secondary?,and thus copper-rich Ti₂Cu grain structure is formed.