Papers by Author: Yue Sun

Abstract: Yttria Stabilized Zirconia (YSZ) films were prepared by electron beam physical vapor deposition (EB-PVD) technique with a high deposition rate up to 1μm/min. An improved sin2ψ method was employed to analyze the residual stress of films by means of grazing incidence X-ray diffraction (GIXRD). The result of residual stress measurement reveals that residual stress of YSZ film is compressive stress and keeps a linear relationship with the deposition temperature, which is induced mainly by the thermal expansion mismatch between the film and substrate. The XRD result of films, prepared with different incident angles, demonstrates that the films show preferred orientation evidently. Furthermore, a parameter ωhkl was introduced from the inverse polar figure measurement theory to reveal the degree of preferred orientation clearly. The calculating result of ωhkl value indicates that the preferred orientation of different specimens changes with the incident angles, which is due to columnar growth pattern of films prepared by EB-PVD. In order to characterize the crystallographic texture visually, XRD with 2D detector system was used to analyze the texture of films. The result shows that Debye rings appear asymmetric intensively, which denotes the existence of preferred orientation directly and agrees with the calculating result of ωhkl value.

Abstract: The process of Electron Beam-Physical Vapor Deposition (EB-PVD) preparing SiC coating by Electron Beam evaporating 3C-SiC ingot on stainless steel (SS) substrate was firstly discussed as a preliminary estimation from thermodynamic viewpoint. The results show that, with the temperature increasing from 2500 to 3400 K, the purity of SiC coating increases from 0.58 to 0.734.

Abstract: Large-sized Fe-based ODS (Oxide Dispersive Strengthen) high-temperature alloy sheets were successfully synthesized by EBPVD (Electron Beam Physical Vapor Deposition) technique. The sheets were about 120μm thick, and having a diameter of 1000mm, whose surface roughness was less than 1μm (Ra<1μm). The microstructures were examined by SEM (Scanning Electron Microscope). The grain size was 1-4μm. When the substrate temperature was 600°C, the sheet had sharp irregular polyhedral grain, and when the substrate temperature was 700°C the sheet had quite regular grains. The morphological orientation angle increased with the distance from the center of the sheet. During the first period of deposition, the sheet was growing in a G-L-S mode, which corresponded with the corn-like microstructure in the cross-section. While during the final period, the sheet changed into a G-S growing mode, which corresponded to the smooth columnar microstructure.

Abstract: Large scale Ni-based alloy sheets are prepared by electron beam physical vapor deposition with and without tungsten added into melting pools respectively. Addition W increased vapor rate and decreased compositional transformation during deposition. Chemical constitution of the sheet prepared through tungsten is more similar to that of the ingot. Microstructure of two alloy sheets is observed by scanning electron microscope (SEM) and atom force microscope (AFM). The results show that both of the sheets consist of columnar grains, whose major axes are almost parallel to the normal direction of the sheet. However, the average diameter of grains of the sheet through tungsten is larger than that of the sheet not through tungsten in minor axis direction. Mechanical properties and failure mechanisms of both sheets are studied. Tensile tests are conducted on a number of specimens. Strength, strain-to-failure are estimated under loading condition. The results show that the sheet prepared by EB-PVD through tungsten has a superior strength and an elongation percentage than that of the one prepared without tungsten.

Abstract: In the process of preparation of high silicon steel by EB-PVD, the effect of distance between ingot and substrate on the weight percent of silicon in the silicon steel was investigated through specially designed experiment. Energy dispersive spectroscopy (EDS), optical microscope (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD) were used to characterize the weight percent of silicon, microstructure, crystal grain size and phase of the high silicon steel. The experimental results show that the weight percent of silicon in the silicon steel decreases with increasing of the distance between ingot and substrate, when the distance is about 415 mm, high silicon steel can be fabricated by EB-PVD. The microstructure of the high silicon steel was composed of columnar crystal grain, the size of the crystal is about 25-50 μm. The material back to the substrate side is composed of B2 and exhibits strong {400} texture.

Abstract: This study concerned with the optimum design, microstructure and mechanical properties analysis of a multi-layered metal/intermetallic materials consisting of Ti and Ti3Al prepared by the electron beam physical vapor deposition (EB-PVD) technology. Based on fracture mechanics and numerical simulation method, the optimized microstructure of Ti-Ti3Al multi-layered materials has been obtained by analyzing the relation curve between structural parameters and work of fracture of materials, then dual-target evaporating method was used to evaporate Ti and Ti-47Al bar alternately to form Ti/Ti3Al thin sheet about 0.12mm thickness. Pattern and phase analysis by SEM and XRD showed that there was homogeneous and continuous interface between layers and the intermetallic layers were made up of α2 phase alloy. The tensile curve of Ti/Ti3Al microlaminates represented the characteristic of multi-layered materials and the maximal extensibility of sample as deposited reached 5.83% and the fracture appearance showed ductile rupture feature.