| 1 | Microstructures and Hardness Properties for β-Phase Ti-24Nb-4Zr-7.9Sn Alloy Fabricated by Electron Beam Melting显示文摘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 a'-martensite.Such phenomenon was also found in deformed gum metals and explained by stress-induced diffusion scattering due to phonon softening. | J.Hernandez S.J.Li E.Martinez L.E.Murr X.M.Pan K.N.Amato X.Y.Cheng F.Yang C.A.Terrazas S.M.Gaytan Y.L.Hao R.Yang F.Medina R.B.Wicker | 2013 | Journal of Materials Science & Technology2013，29，11： | 8 |
| 3 | Tuning thermal expansion by a continuing atomic rearrangement mechanism in a multifunctional titanium alloy显示文摘As to multifunctional titanium alloys with high strength and low elastic modulus, thermal training is crucial to tune their thermal expansion from positive to negative, resulting in a novel linear expansion which is stable in a wide temperature range. Aided by the high-order Hooke's law of elastic solids,a reversible atomic rearrangement mechanism was proposed to explain the novel findings which are unexpected from typical shape memory alloys. To confirm this continuous mechanism, a Ti-Nb based alloy, which possesses a nanoscale spongy microstructure consisting of the interpenetrated Nb-rich and Nb-lean domains produced by spinodal decomposition, was used to trace the crystal structure change by in-situ high energy synchrotron X-ray diffraction analyses. By increasing exposure time, the overlapped diffraction peaks can be separated accurately. The calculated results demonstrate that, in the nanoscale Nb-lean domains, the crystal structure parameters vary linearly with changing temperature along the atomic pathway of the bcc-hcp transition. This linear relationship in a wide temperature range is unusual for first-order martensitic shape memory alloys but is common for Invar alloys with high-order spin transitions. Furthermore, the alloy exhibits smooth DSC curves free of transformation-induced heat peaks observed in shape memory alloys, which is consistent with the proposed mechanism that the reversible transition is of high-order. | D.L.Gong H.L.Wang E.G.Obbard S.J.Li R.Yang Y.L.Hao | 2021 | Journal of Materials Science & Technology2021，，21： | 0 |
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