Papers by Author: Ying Liu

Abstract: WC-Ni-Cr composite cladding is fabricated on the Q235 steel by infiltration brazed in a vacuum furnace. Microstructure of interface and welding specimen's longitudinal section of alloy coating are investigated by CMM-88E metallographic microscope and FEI Quanta200 scanning electron microscope. Element diffusion and distribution along the longitudinal section are tested by the Energy Disperse Spectroscopy (EDS), produced by Oxford Corporation; Influencing factors of the coating's brazed interface are analyzed. The results show that when nickel base coating powders are used for infiltration brazed, the BNi-2 solder is appropriate and the appropriate temperature should be in 1120~1140 °C. The welding interface of vacuum brazing compact very well and the existence of element diffusing forms the metallurgy welding contact surface.

Abstract: A series of Ti/TiN multilayer films were prepared by reactive DC magnetron sputtering onto Si(111) substrates. The resistivity and optical reflectance of these thin films were measured as a function of the modulated, multilayered thickness and the number of layered structures. The resistivity decreased with increase in the number of layers in the film up to 4 layers. The reflectance in the near infrared region increased with increase in layer thickness but after a certain thickness, the change in reflectance was minimal. An optimum thickness of 25 nm for the modulated film realized a maximum of 0.829 in the near infrared reflectance. With the number of layers greater than 15, an interfacial layer of Ti2N was observed.

Abstract: A series of Ti/TiN multilayer films was deposited on Si substrates by DC reactive magnetron sputtering process. The influence of sputtering current density and substrate temperature on cycle membrane structure and its electrical properties was investigated in this study. The results show that: when the current density is 0.4A, the sheet resistance and electrical resistivity of the film are of the minimum value. The sheet resistance and electrical resistivity of the film decrease with an increase of substrate temperature. Therefore, sputtering current density should be controlled between 0.3-0.4A, while the substrate temperature should be above 400°C. For a given modulation period and modulation ratio, with the change of number of cycles the films can present a unique set of colours, and its electrical resistivity decreases with an increase in the number of cycles. When the number of cycles is greater than 4, the sheet resistance is significantly reduced, and when the number is greater than 15, the prepared films come off. To keep the number of cycles at five and change the modulation period, it is shown that a minimum electrical resistivity exists.

Abstract: Butt welding of 0.2mm thick TiNi shape memory alloy sheet was successfully realized by using micro impulse laser whose average power is 80W and the microstructure of welded joint was study in this paper. The results show that, the welded joint of micro laser welding can be divided into four zones according to grain size and microstructure. The microstructure in base metal zone is rolled structure and the grains are coarse and heterogeneous. The microstructures of welded seam center zone are fine equiaxed crystals and the microstructures of both lower surface and upper surface edge zone are columnar crystals. There is almost no obvious coarse grain heat-affected zone at the edge between welded seam and base metal. There is obvious segregation layer in local area of welded seam because the content of Ti and Ni elements is changed and different with base metal during the crystallizing course of welding pool.

Abstract: Two-dimensional micro mix driven by electroosmotic flow was studied by finite element simulation and mixes speed of microchannels with unified zeta potential of the wall surface and the polar opposite one was contrasted. Relation between the section shape of the microchannels and the speed of mixing is cleared when the wall surface has the polar opposite zeta potential. The results show that section mixing speed of microchannel whose wall surface with unified zeta potential is lower than the one with polar opposite wall surface zeta potential. The ratio of width to height in microchannels of homolographic rectangle section and the height of microchannels with isosceles trapezoid section also have influence on mixing speed. When former increases or later decreases the mixing speed rapidly increases and then drops slowly. The mixing speed arrived at maximum value when the former and the later are 1.44 and 10μm, respectively.