| Titanium alloys of bioengineering have been widely used as hard tissue repairing and replacing materials, such as body skeletons and teeth etc, due to their high strength ,high contrast- strength and excellent corrosion resistance. However, there are many shortages in titanium alloys used in bioengineering, toxicity of alloying element such as Al and V, and high moduli of elasticity. Otherwise, many researches have been done on the investigation and exploitation of β titanium alloys ,because of their low moduli of elasticity and upstanding integrate mechanical properties,comparing with α and α + β titanium alloys. But little investigation has been done about the effect of elements Ta and Zr on microstructure and mechanical properties. We investigate the effect of element Ta and Zr, basing on Ti-20Nb alloys, and offer the theoretic foundation, aiming at these issues.A new β titanium alloy, Ti-20Nb-10.5Tα-13Zr, was designed for bioengineering application. Microstructure , moduli of elasticity, mechanical properties and corrosion resistance(in body fluid) of the alloy were investigated in this paper.After solution treatment, long needle-like α " martin formed in the base of β and grew up with the increasing of element Ta, for the Ti-20Nb-Ta series alloys contained 8 ～ 15.5% Ta. After aging treatment, metastable α " decomposed to α+β , which developed with the increasing temperature of aging. The strength of Ti-20Nb-Ta series alloys were improved and plasticity still kept high level, comparing with Ti-20Nb alloy. The modulus of elasticity of alloy increased then decreased, and next increased again. When alloy contained 10.5% Ta, E value achieved low level: after solution treatment E=60GPa, after aging treatment E=65GPa. When Ta exceeded 13%, E obviously increased.After solution, β +α " microstructure formed in the Ti-20Nb-10.5Ta-Zr series alloys, contained 5～17% Zr. After aging, metastable α " decomposed...
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