Microstructure, Mechanical Properties, and Springback of Ti-Nb Alloys Modified by Mo Addition
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Microstructure, Mechanical Properties, and Springback of Ti-Nb Alloys Modified by Mo Addition Qiang Li
, Ran Zhang, Junjie Li, Qiang Qi, Xuyan Liu, Masaaki Nakai, Mitsuo Niinomi, and Takayoshi Nakano
(Submitted January 31, 2020; in revised form June 16, 2020; published online August 12, 2020) A series of Ti-(38-2x)Nb-xMo (wt.%) alloys are designed using 1% Mo to replace 2% Nb in order to gradually increase the b stability and obtain a low springback. The a¢¢ phase is exhibited in Ti-38Nb and suppressed with an increasing Mo content. The Ti-38Nb and Ti-34Nb-2Mo alloys show stress-induced a¢¢ martensite transformations during cold rolling and double yielding behavior in tensile tests. The Ti-30Nb4Mo and Ti-26Nb-6Mo alloys exhibit nonlinear deformation owing to the metastable b phase. With an increase in the Mo content, Youngs modulus increases slightly from 68 GPa in Ti-38Nb to 73 GPa in Ti26Nb-6Mo, owing to the increase in b stability. Mo shows a solution strengthening effect that gradually increases the tensile strength. Although a higher Youngs modulus was not observed to be induced through deformation in Ti-(38-2x)Nb-xMo alloys, low springback was obtained according to the three-point bending loading–unloading test. In particular, the Ti-38Nb and Ti-34Nb-2Mo alloys with stress-induced a¢¢ martensite transformations exhibit low yielding stress and are thus easily deformed. The deformed a¢¢ phase hardly reverts to the b matrix after unloading, and therefore, the plastic deformation is maintained. Keywords
biomaterials, cold rolling, springback, Ti alloys, Youngs modulus
1. Introduction Ti and its alloys are widely used as biomaterials owing to their excellent biocompatibility, high corrosion resistance, specific strength, and low Youngs modulus (Ref 1-4). Although commercial pure Ti (C.P.-Ti) and Ti-6Al-4V ELI (extra low interstitials) are widely used in clinical applications, they are not perfect candidates. C.P.-Ti exhibits low strength Qiang Li, Ran Zhang, Qiang Qi, and Xuyan Liu, School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, Peoples Republic of China; Junjie Li, CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics & Chemistry, CAS; Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, U¨ru¨mqi 830011, Peoples Republic of China; Masaaki Nakai, Department of Mechanical Engineering, Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashiosaka, Osaka 577-8502, Japan; Mitsuo Niinomi, School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, Peoples Republic of China; Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980–5377, Japan; Department of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871, Japan; Department of Materials Scien
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