Abstract
Ti-(5–20)Nb-(0.5–1)O alloys (mass%) were investigated for developing low-cost biomedical α+β-type Ti alloy. Ti-(5, 10, 15, 20)Nb-(0.5, 0.75, 1)O alloys (mass%) were arc-melted and forged into bars. The forged alloy bars were heat-treated at 873 to 1373 K for 3.6 ks in an Ar atmosphere and quenched in iced water. β transus (Tβ) of the Ti-Nb-O alloys decreased with increasing Nb content. An increase in the oxygen content led to an increase in Tβ. After quenching, the formation of α′ martensite was observed in Ti-5Nb-yO alloys. An increase in the Nb content to 10 mass% led to the formation of α′ and α″ martensites. A further increase in the Nb content to 15 and 20mass% resulted in the formation of more α″ martensites. The boundary temperature for the formation of α′ and α″ martensite in the Ti-10Nb-yO alloys increased with increasing oxygen content, because oxygen enhances the Nb distribution to the β phase. The ultimate tensile strength of the Ti-xNb-0.75O alloys heattreated to obtain the α-phase fraction (fα) of 0.5 was over 1000 MPa, except for the Ti-15Nb-0.75O alloy. The total elongation decreased with increasing Nb content. The Ti-5Nb-0.75O alloy exhibited excellent strength-ductility balance as a low-cost α+β-type biomedical Ti alloy.
Highlights
Ti and its alloys have several applications, such as artificial joints, bone plates, and dental implants, as biomedical materials because of their excellent corrosion resistance, mechanical properties, and biocompatibility.[1]
The α+β-type Ti alloys exhibit a wide range of mechanical properties, which are achieved by the tailoring of volume fraction and grain size of the equiaxed α phase through thermomechanical processing.[2]
It is well known that the production cost of Ti and its alloys is high, and the utilization of ubiquitous elements has been suggested as an effective method of cost reduction for Ti alloys.[3]
Summary
Ti and its alloys have several applications, such as artificial joints, bone plates, and dental implants, as biomedical materials because of their excellent corrosion resistance, mechanical properties, and biocompatibility.[1]. [9,10] V is a β-isomorphous-type element and does not form any intermetallic compounds with Ti. Our previous work investigated the microstructure and mechanical properties of α+β-type Ti-(0–10)V-(0.5–1)O alloys (mass%) using oxygen as an alloying element.[9] Among them, the Ti-4V-0.6O alloy (mass%) exhibited an excellent strength–ductility balance without the formation of athermal ω. We focused on Nb as an alloying element of low-cost biomedical α+β-type Ti alloy. Nb is a β stabilizer and β-isomorphous element with high oxygen solubility It is used as an alloying element for biomedical β type Ti alloys. To develop biomedical α+β-type Ti-Nb-O alloys, the effect of Nb and oxygen on the microstructure and mechanical properties was investigated
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