Studies of Microstructures and Mechanical Properties for Ti, Zr-Based Biomedical Alloys
|School||Beijing University of Technology|
|Course||Condensed Matter Physics|
|Keywords||Ti-Ta-Nb alloy Zr-Ta-Nb alloy Precipitate phases Transmission electron microscopy Electron diffraction indexing the strain-induced martensite|
Biomedical Materials are aimed at medical treatment; they can be used for the diagnosis, treatment, rehabilitation or replacement of human tissues or organs to enhance their functions. As biomedical materials, metallic materials come into use more earlier than other materials. In particular, among them Ti and Ti-based alloys have been widely used in transplant surgical due to their good mechanical properties, good biocompatibility and excellent processing performances. In recent years, the development of newβ-type biocompatible Ti-based alloys which have better biocompatibility and lower modulus has become a most attractive research field. It is very important to clarify the characteristics of various phase transformation and related microstructural variations inβ-type Ti-based alloys in order to obtain valuable information for improvement of mechanical properities and development of newβ-type Ti-based alloys.In the present study, we started with an effort to develope new biocompatible alloys. With the aid of the d-electron theory for Ti alloys together with Kβparameter calculations, we designed and prepared aβ-type Ti-25.6Nb-19.4Ta(wt%) alloy for biomedical applications.Mechanical properties testing has been conducted to this new biocompatible alloy and compared with other prepared Ti-based alloys with different compositions. The results show that Ti-25.6Nb-19.4Ta alloy has relatively low elastic modulus. The Ti-25.6Nb-19.4Ta alloy has a good aging response, and its hardness, strength and plasticity can vary significantly due to suitable ageing treatments. . By means of X-ray diffraction and transmission electron microscopy techniques, the effects of aging treatments on microstructures of the Ti-25.6Nb-19.4Ta alloy have been studied, through which the precipitation behaviors related to the variations of mechanical properties for the alloy aged at 400℃for different periods of time have been clearly revealed.Subsequently, the biocompatible and aging-hardenable Zr65Ta12Nb23 (at%) alloy of theβ-type has also been studied in this paper. On the basis of electron diffraction simulations and indexing analysis, the nano-sized precipitate formed in the early stage of aging treatmeat, named asαx phase, has been identified to have a hexagonal structure and its lattice parameters determined to be a = b = 0.362nm, c = 0.764nm,α=β=90o,γ=120o, respectively. Unlike the equilibriumα-phase, theαx phase orientationally related to itsβ-matrix through Pistch-Schrader relationship in stead of Burgers relationship.In addition, the compressive deformation structure of the suction-cast Zr65Ta12Nb23 alloy has been examined by transmission electron microscopy observations. A kind of strip-shaped phase was found to form due to the deformation. Through electron diffraction calculation and indexing analysis, this strip-shaped phase has been identified to be a strain-inducedα′martensite, and its lattice parameters determined to be a=b=0.3307nm,c=0.4765nm,α=β=90o,γ=120o, respectively.