Microstructure and mechanical properties of Ti-Mo and Ti-6Mo-X-Y alloys

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Abstract

In this study, we investigated the microstructure, hardness, Young's modulus, and tensile behavior of binary Ti-4∼9 mass% Mo alloys, quenched from a temperature of 1223 K. Among the solution-treated binary Ti-Mo alloys, the lowest Young's modulus was observed in the case oftheTi-6Mo alloy, which was the border composition of α′ /α′. When the rolling deformation of 2%reduction was carried out, the Young's modulus of Ti-Mo alloys having less than 6 mass% Mo increased, whereas that of higher than 6 mass.% Mo reduced. The Young's modulus ofthe 6Mo alloy hardly changed with the rolling deformation. Ti-6Mo-X-(Y) alloys, where X and Y are 1 mass% of Al, Sn, Cr, and Fe, were prepared in order to investigate the influence of additional elements on the microstructure and mechanical properties ofthe 6Mo alloy. The phase constitution of quenched Ti-6Mo-X-Y alloys mostly corresponded with the value of the Mo equivalency (Moeq); however, Ti-6Mo-l Al-lFe (MAF) and Ti-6Mo-lFe (MF) exhibited slightly more β-rich structures for their respective Moeq values. The lattice parameters "a" and "b"of the α"-structure in the Ti-6Mo-X-Y alloys changed with Moeq in a manner similar to that in the Ti-Mo alloy; however, "c"exhibited a different behavior. The mechanical properties of Ti-6Mo-X-Y alloys except for the MF alloy were similar to those of Ti-Mo alloys corresponding Moeq. However, the Young's modulus of the Ti-6Mo-X-Y alloys was greater than that of the 6Mo alloy. The tensile properties of the MF alloy having β+ω structure were extremely unstable with respect to the fracture elongation. This peculiar behavior is attributed to the occurrence of deformation-induced β+ωα′ transformation. The formation of the α′ structure caused significant softening and local intense deformation in the α′ phase resulted in a brittle fracture. On the other hand a successive α′ formation induced by work hardening would result in good ductility. It was suggested that the unstable elongation inthe MF alloy resulted from competition between the reverse effects.

Original languageEnglish
Pages (from-to)752-757
Number of pages6
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume73
Issue number9
DOIs
Publication statusPublished - Sep 1 2009

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Keywords

  • Stress induced transformation
  • Tensile property
  • Young's modulus
  • α′-martensite
  • α″-martensite
  • ω-phase

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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