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Microstructures and Hardness Properties for b-Phase Tie24Nbe4Zre7.9Sn Alloy Fabricated by Electron Beam Melting

J. Hernandez1), S.J. Li2), E. Martinez1), L.E. Murr1), X.M. Pan3), K.N. Amato1), X.Y. Cheng2),F. Yang2), C.A. Terrazas4), S.M. Gaytan4), Y.L. Hao2), R. Yang2), F.Medina4), R.B. Wicker4)   

  1. 1) Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA
    2) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 11016,China
    3) School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
    4) W. M. Keck Center for 3D Innovation, The University of Texas at El Paso, El Paso, TX 79968, USA
  • Received:2013-06-18 Revised:2013-09-19 Online:2013-11-30 Published:2013-11-06
  • Contact: L.E. Murr

Abstract:

Atomized, pre-alloyed Ti–24Nb–4Zr–7.9Sn (wt%) powder was used to fabricate solid, prototype components by electron beam melting (EBM). Vickers microindentation hardness values were observed to average 2 GPa for the precursor powder and 2.5 GPa for the solid, EBM-fabricated products. The powder and solid product microstructures were examined by optical and electron microscopy. X-ray diffraction analyses showed that they had bcc β-phase microstructure. However, it was found by transmission electron microscopy that the EBM-fabricated product had plate morphology with space ∼100–200 nm. Although the corresponding selected area diffraction patterns can be indexed by β-phase plus α″-martensite with orthorhombic crystal structure, the dark-field analyses failed to observe the α″-martensite. Such phenomenon was also found in deformed gum metals and explained by stress-induced diffusion scattering due to phonon softening.

Key words: Biomedical titanium alloy, α″-Martensite, Electron beam melting, Hardness, Optical and electron microscopy