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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.58  No.2 (2017)  >  pp.271-279

MATERIALS TRANSACTIONS
<<Previous article Vol.58  No.2 (2017)   pp.271 - 279 Next article>>

Effects of Mo Addition on the Mechanical Properties and Microstructures of Ti-Mn Alloys Fabricated by Metal Injection Molding for Biomedical Applications

Pedro Fernandes Santos1), Mitsuo Niinomi2) 3) 4) 5), Ken Cho3), Huihong Liu6), Masaaki Nakai7), Takayuki Narushima1), Kyosuke Ueda1), Yoshinori Itoh8)
1) Graduate School of Engineering, Tohoku University 2) Graduate School of Science and Technology, Meijo University 3) Graduate School of Engineering, Osaka University 4) Institute of Materials Research, Tohoku University 5) Materials and Systems for Sustainability, Nagoya University 6) Joining and Welding Research Institute, Osaka University 7) Department of Mechanical Engineering, Faculty of Science and Engineering, Kindai University 8) Hamamatsu Technical Support Center Industrial Research Institute of Shizuoka Prefecture

Ti-Mn alloys fabricated by metal injection molding (MIM) show promising performance for biomedical applications, but their low ductility (caused by high O content and the presence of pores and carbides) requires improvement. Previously, the addition of Mo to cold crucible levitation melted (CCLM) Ti-Mn alloys efficiently improved the ductility of those alloys by promoting mechanical twinning. In the present study, Mo was added to Ti-Mn alloys fabricated by MIM. Unlike fabrication by CCLM, fabrication by MIM can produce alloys with a smaller grain size, and also introduce microstructures such as pores and Ti carbides. Thus, in order to investigate how Mo addition interacts with these typical MIM features, four alloys for biomedical applications were fabricated by MIM: Ti-5Mn-3Mo (TMM-53), Ti-5Mn-4Mo (TMM-54), Ti-6Mn-3Mo (TMM-63), and Ti-6Mn-4Mo (TMM-64). Their microstructures, mechanical properties, and tensile deformation mechanisms were evaluated. Their hardness values range from 312–359 HV, and their Young's modulus values range from 84–88 GPa; both the Vickers hardness and Young's modulus show little variation among the alloys. Although the alloys show fracture features associated with a predominantly ductile fracture mode and Mo addition successfully promotes mechanical twinning in TMM-54, the elongation of these alloys is still critically low. Compared to the TMM alloys fabricated by CCLM, the TMM alloys fabricated by MIM show slightly lower hardness and Young's modulus, and comparable tensile strength, with their low elongation remaining inadequate for such applications. In particular, TMM-63 shows the best combination of mechanical properties among the present alloys, with an elongation of 4% and an ultimate tensile strength of 1145 MPa.




Keyword:
titanium-manganese-molybdenum alloys, β-phase, mechanical properties, deformation mechanisms, metal injection molding

Received: August 18, 2016
Accepted: November 21, 2016 , Published online: January 25, 2017

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