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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.45  No.7 (2004)  >  pp.2449-2455

MATERIALS TRANSACTIONS
<<Previous article Vol.45  No.7 (2004)   pp.2449 - 2455 Next article>>

Microstructures and Mechanical Behaviors of Ti-30Nb-1Fe-xHf Alloys

Yen-Huei Hon1), Jian-Yih Wang2) and Yung-Ning Pan1)
1) Department of Mechanical Engineering, National Taiwan University Taipei
2) Materials & Electron-Optics Research Division, Chung-Shan Institute of Science and Technology


Effects of iron (1 mass%) and hafnium (1—7 mass%) on the microstructure and mechanical properties of Ti-30Nb base alloys were investigated in this study. Experimental results indicate that the addition of 1 mass% Fe to the Ti-30Nb alloy transforms the original α + β + ω structure into a single β phase structure. Accompanying the structure change, both the tensile strength and 0.2% proof stress were reduced by some 15%, while the elastic modulus was reduced from 80 GPa to 68 GPa. Regarding the effect of Hf, precipitation of sporadic ω phase in the otherwise complete β phase structure can be detected when hafnium is added. An addition of just 1 mass% Hf to the Ti-30Nb-1Fe alloy increases the tensile strength and 0.2% proof stress by 32% and 27%, respectively, while slightly decreasing the elastic modulus by some 10%. The Ti-30Nb-1Fe-1Hf alloy has relatively high strength (∼914 MPa T.S.), reasonable ductility (∼10% El), and an elastic modulus of around 62 GPa. Consequently, the ratio of 0.2% proof stress to elastic modulus increases moderately. The ratio of 0.2% proof stress to elastic modulus of Ti-30Nb-1Fe-1Hf was found to be 1.39 × 10−2, which was around 1.8 times higher than Ti-6Al-4V (0.78 × 10−2), and around 3.5 times higher than c.p.Ti (0.4 × 10−2). Hafnium content exceeding 1 mass% gives no further improvement in the ratio of 0.2% proof stress to elastic modulus. From the results obtained here, Ti-30Nb-1Fe-1Hf alloy has excellent potential for orthopedic implant applications.


Keyword:
Titanium-niobium-iron-hafnium alloys, microstructure, mechanical properties

Received: March 18, 2004
Accepted: June 01, 2004 , Published online: June 24, 2005
Copyright (c) 2005 The Japan Institute of Metals

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