Room Temperature Deformation Characteristics And Elastic Behavior Of Medical Near-? Type TLM Alloy

Titanium alloys are widely used in biomedical materials due to their excellent biocompatibility,corrosion resistance and comprehensive mechanical properties.Recent research results show that ?-titanium alloy in titanium alloy has been widely recognized because of its low elastic modulus,easy-to-regulate microstructure and certain superelastic properties.However,the existing research on ?-type titanium alloy still has certain problems,such as the strength,plasticity and elastic modulus does not reach the excellent matching,and the relationship between the microstructure,deformation characteristics and elastic properties of the material there are few studies.Therefore,based on the key projects of Shaanxi Province,this paper studies the TLM near-?-type titanium alloy with low modulus and excellent mechanical properties developed by the Institute of Biological Research of Northwest Nonferrous Metals Research Institute,and the relationship between micro structure,deformation characteristics and elastic properties was discussed.A TLM alloy ingot is prepared by a vacuum consumable melting furnace,and is subjected to blank forging,hot rolling,and straightening to obtain a bar of a specification size.The alloy bar is subjected to heat treatment under different conditions,and the microstructure property is tested to analyze the influence of heat treatment on the structure and properties.The microstructure of the sample after tensile deformation was examined,and the deformation characteristics of the material were analyzed by comparison with the micro structure before deformation.The stress-loading unloading test was used to characterize its superelastic properties and analyze its association with microstructure.Finally,the effect of different deformation conditions on the microstructure and properties of swaging was discussed.The main conclusions of the experiment are as follows:The effects of heat treatment on the microstructure and properties of TLM alloy were analyzed.The results show that the microstructure consists of a,? phase and quenching ?"phase in the solution treatment of the two-phase zone.In the singlephase zone solution treatment,the structure is mainly composed of equiaxed ? phase and quenched?" phase..The tensile strength of the single-phase zone solid solution alloy is 550 MPa,the elongation is 44%,and the two-phase zone solid solution alloy is strengthened by the fine a phase of the grain boundary,the tensile strength is increased to 620 MPa,the elongation is reduced to 28%.After 750? solution treatment,the secondary a phase in the ? crystal precipitated and gradually grew with the increase of aging temperature.When the aging temperature is 300?,the isothermal ? phase precipitated in the ? phase,which significantly increased the tensile strength.With the aging time prolonged,the isothermal ? phase gradually increases,the tensile strength of the sample gradually increases,but the plasticity is decreases.The room temperature deformation characteristics of materials with different heat treatment conditions were analyzed.The results show that the solid solution TLM alloy in single-phase zone has a work hardening rate of 1100 MPa in the uniform plastic deformation zone.This high SHR value and excellent strength plasticity matching is usually accompanied by a high incidence of twins and the occurrence of induced martensitic transformation to coordinate deformation.For the alloy samples treated in the single-phase zone with solid solution and low temperature aging for different time,there is ?" induced martensite phase and deformation twins in the microstructure of the deformed specimen for aging 30 min.With the extension of aging time,the martensitic transformation stress is gradually increased,so the phase transformation is difficult to occur.During the deformation process,deformation twins and dislocation slip are used to coordinate the deformation.The effects of different microstructures on the superelastic properties of the materials were analyzed.The results show that the superelastic properties of the twophase region solid solution alloys are better than the single-phase region.The singlephase region solid solution alloys has more quenching ?" phase,which is prone to plastic deformation,so the martensite phase is less induced under small strain conditions and the superelastic properties are poor.During the aging process,the superelastic properties of the material gradually decrease with the aging time prolongs,which is because the ? phase precipitated in a short period of time is relatively small.When the loading strain is 2%,the maximum recoverable strain is 1.9%.The effects of different conditions of swaging deformation on the microstructure and properties of the material were analyzed.The results show that the cold swaged specimen has uniform microstructure and the deformation produces many fine grains and substructures.When the deformation is 40%,the strength reaches 1000 MPa,the elongation is 14%.The deformation structure of the 300? warm swaged is not uniform,and there are many fibrous deformation zones in the deformation zone.When the deformation is 40%,the strength reaches 844 MPa,and the elongation is 19%.Compared with the solid solution alloys,the superelastic properties of the alloy after swaged deformation are significantly improved.The presence of fine grains and substructures in the microstructure after deformation helps to improve the superelastic properties of the material.