| The materials, used for the replacement of hard tissues such as artificial bones, artificial joints and artificial dental implants have become the research hotspot in any country with its widely application and huge requirement. With the excellent biocompatibility, corrosion resistance and near-bone elastic modulus, pure titanium and its alloys are becoming more and more widely used in medical fields and creating huge social benefit and economic value.According to exploitation status quo and existing flaws of titanium alloys for surgical implants, a new near β titanium alloy Ti-29Nb-13Ta-4.6Zr for surgical implants is designed and fabricated. The mechanical properties and microstructure of Ti-29Nb-13Ta-4.6Zr alloy have been studied systematically with different working processes(two forging temperatures above β -phase transition temperature), solid solution treatments(40~ 50 ℃ above β -phase transition temperature), cooling rate (water quenching), aging treatments(two aging temperatures and different aging time). The processes resulting in the lower elastic modulus, higher tensile strength, toughness and their influential factors have been investigated. The main results are summarized as follows:The cast Ti-29Nb-13Ta-4.6Zr alloy has a few gas holes and shrinking holes. After forging and solution treatment, the structure of alloy is single metastable beta phase. The strength and elastic modulus are low. After aging treatment at two different temperatures, the strength and elastic modulus increase with the decrease of elongation.With the increase of aging temperature, the tensile strength decreases . with the increase of elongation. The direct reason for the change of mechanical properties of the alloy is size, quantity and distribution of alpha phase in the matrix. With aging temperature raised, the alpha phase becomes thicker and longer along with longer distance between the precipitations during the test process so that the strengthening action of the alpha phaselessens which cause the lower strength and higher elongation of the alloy. Meanwhile, the dispersion degree of alpha phase decreases with the increase of aging temperature. All these factors make the strengthening effect better under lower aging temperature (350℃) treatment.With the increase of aging time, the alpha strengthening phase become more in number and bigger in size gradually. At the same time, with the increase of aging time, the alpha phase become thinner and longer with the shorter distance between precipitation phase. These alpha phases mainly distribute in equilibrium beta phase matrix and coexist with beta phase. With the increase of aging time, the tensile strength and elongation decrease obviously under aging treatment at 350℃ .For the alloy treated by age at 450℃, the effect of aging time on mechanical properties is opposite to the effect of aging temperature on mechanical properties. With the increase of aging time, the strength of the alloy increases with the decrease of elongation.According to the necessity of the mechanical biocompatibility for biomedical Titanium alloys, the optimum matched mechanical properties of Ti-29Nb-13Ta-4.6Zr alloy can be required when the studied alloy was solution treated under( β )phase temperature and then water quenching, then was aging treated at 450℃ for 194.4ks, which shows the result: σ 0.2=448MPa, σ b=520MPa, δ =3.1%, E=59Gpa... |
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