Y. C. Lei

Harbin Institute of Technology, Charbin, Heilongjiang Sheng, China

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Publications (4)5.04 Total impact

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    ABSTRACT: The Ti49Ni46.5Ce4.5 alloy thin film was prepared by direct current (DC) magnetron sputtering system for the first time. Crystallization kinetics, phase composition and the behaviors of martensitic transformation were studied. The results by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) demonstrated that the primary second phase of TiNiCe alloy thin films was Ce2Ni7 phase, apparent activation energy was determined to be 510 kJ/mol at the continuous heating process, Avrami exponents for different isothermal temperature were in the range of 1.1–1.88 between 713 and 730 K, one-step martensitic transformation was observed in the crystallized Ti49Ni46.5Ce4.5 alloy thin films. The influence of thermal process on martensitic transformation temperature was investigated with non-isothermal and isothermal crystallization. The reason behind the transformation temperature change was also discussed.
    Vacuum. 01/2010; 84(9):1138-1141.
  • H. B. Wang, C. Liu, Y. C. Lei, W. Cai
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    ABSTRACT: The Ni55.6Mn11.4Fe7.4Ga25.6 high temperature shape memory alloy thin film was deposited onto silicon substrates by using radio-frequency (R.F.) magnetron sputtering technique. Surface morphology, crystallographic structure, martensitic transformation and microstructure were systematically investigated by means of scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that the film has columnar structure and an excellent surface quality. The film has seven-layered modulated orthorhombic structure with typical self-accommodated morphology at room temperature. The martensitic transformation start temperature of the film is up to 439K, much higher than room temperature, displaying the promising application as high temperature actuator material.
    Journal of Alloys and Compounds 01/2008; 465(1):458-461. · 2.73 Impact Factor
  • Y. C. Lei, W. Cai, X. An, L. X. Gao
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    ABSTRACT: The crystallization kinetics of amorphous thin TiNi films deposited on SiO2 (or NaCl)/Al foils substrates were investigated. A dramatic acceleration of the crystallization rate was observed for amorphous attached-substrate films. The acceleration originated from the presence of the thin film/middle-wafer interface which served as a two-dimensional nucleus for the growth of the crystalline phase. In the process of non-isothermal annealing by DSC, apparent activation energies for two kinds of underlying thin TiNi films were determined to be 352.96 and 403.69kJ/mol, respectively, which was lower than those free-standing films studied in previous works. For the process of isothermal annealing, the crystallization kinetics parameters had remarked drop, reflected from the lower Avrami exponent n (the range of 1.35–2.11) and shorter incubation time τ (the range of 0.1–0.4min) between 758 and 775K.
    Journal of Non-crystalline Solids - J NON-CRYST SOLIDS. 01/2008; 354(40):4572-4576.
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    ABSTRACT: In the present work, 1 at% Y was added to Ti-50.7at%Ni alloy to prepare Ti-50.2Ni-1Y alloy and the effects of rare earth Y addition on the microstructure and martensitic transformation behavior of Ti-50.7at%Ni alloy was investigated by optical microscope, scanning electronic microscope (SEM) X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show the microstructure of Ti-50.2Ni-1Y alloy is different with that of Ti-50.7at.%Ni alloy, and its microstructure consists of B19′martensite and the Y-rich phase, which may be YNi phase. One-step martensitic transformation occurs in Ti-50.2Ni-1Y ternary alloy. The phase transformation temperatures increase rapidly with Y addition, and the increase of Ms is about 85°C.
    Journal of Materials Science 01/2007; 42(14):5791-5794. · 2.31 Impact Factor