Yin Qun Hua

Influence of High Temperature Processing on the Substructure of Laser Shock Processed Titanium Alloy

The paper aims to study the influence of high temperature processing on the substructure of laser shock processed titanium alloy. The titanium alloy specimens were first treated by laser shock processing (LSP), then treated at 700°C for three hours and air cooled to the room temperature to investigate the influence of the high temperature processing. To evaluate such influence, the hardness and substructure on the surface were investigated by micro hardness tester and transmission electron microscope (TEM), respectively. Results show that after three times LSP, the hardness of TC11 alloy was improved by 30.9%. The cause of such an improvement in hardness is that the crystal grains in the surface layer under the shock wave stress were strongly deformed, causing a dynamic recrystallization. The substructure is mainly twin crystals, highly tangled and dense dislocations. After high temperature processing in vacuum, the average hardness is decreased by 12% compared to that of the specimens after LSP. And the substructures are mainly small dislocation, nanocrystalline.

Study on the Property of Bi2(Mg2/3Nb1.1833Sn0.15)O7 Dielectric Ceramics Doped with Li2CO3

(Bi2-xLix) (Mg2/3Nb1.1833Sn0.15)O7 piezoelectric ceramics were prepared by conventional solid state reaction method. The microstructure and dielectric properties of dielectric ceramics were studied which was doped by different amount of Li2CO3. The experiment results showed that the density of the ceramics would decrease, but have little effect on the microstructure of the ceramics when the amount of the Li2CO3 doped increases. With the increasing of Li2CO3 doped, the dielectric constant(εr) and dielectric loss(tanδ) of dielectric ceramics first decreases and then increases. When tested in 1MHz frequency, the piezoelectric ceramics display the optimum properties tanδ is 0.00009, εr is 163 while Li2CO3 doped amount is 0.05 mol%.

Mechanism of Improving Mechanical and Electrical Properties of Fe40NiCrSiAl Alloy Induced by Laser Shock Wave

This paper explores the properties of Fe40NiCrSiAl alloy treated by different methods. The hardness, elastic modulus and resistivity are tested. The results indicate that: after LSP to rolled Fe40NiCrSiAl alloy, the hardness increased 25.22%, the elastic modulus increased 7.17% and the resistivity decreased 39%. TEM photographs demonstrated that there appeared dislocations, martensite transformation and twin crystals inside the material after being treated by LSP. Twin crystals are the main reason attributing to the improvement of material electrical properties.

Study of Structure and Optical Properties of Magnetron Sputtered ZnS Thin Films by Annealing

Nanocrystalline ZnS thin films were deposited on glass substrates at 300W and 0.6Pa by using radio frequency magnetron sputtering, and then annealed at different temperatures. This work investigated the influence of ZnS buffer layer on different annealing temperature, analysed structural, surface topography, and optical properties of ZnS films by using X-ray diffraction (XRD), UV-spectroscopy measurements and scanning electronic microscope (SEM) analysis techniques. Findings showed that the film annealed at 300°C was uniformity and compact, which was zinc blende cubic structure. The film exhibited the optical transparency as high as 85% in the visible region, and its optical band gap was calculated to be 3.56 eV.

Structures and Properties of ZnO-Based Ceramic Films for Low-Voltage Varistors by the R.F. Magnetron Sputtering

ZnO-based ceramic targets with 50mm in diameter and 3mm in depth were prepared by the traditional solid-state sintering process. ZnO-based ceramic films were deposited on Au/Si substrates by R.F. magnetron sputtering using ZnO-based ceramic target. The films have been characterized by X-ray diffraction, energy dispersive X-ray spectroscopy and scanning electron microscopy. The ZnO-based ceramic films, with thickness close to 1 μm, show a good c-axis orientation, corresponding to vertical growth with respect to the substrate. The surface of the films looks very smooth and dense, and the films are the same composition as the ZnO ceramic target composed of Zn, Bi, Sb, Co, Cr and Mn. The ZnO-based ceramic films with nonlinear coefficient of 6.4, nonlinear voltage of 1.6V and the leakage current density 0.3μA/mm2 could be achieved.

The Research on the Action Modes of Laser Shock Wave Affected by Different Confinement Overlays

The liquid confinement medium (LCM) and the free confinement medium (FCM) made by ourselves were used as confinement overlays of laser shock processing (LSP) respectively, stainless steel 304 was shocked by Nd:Glass laser. The parameters of LSP are the wavelength of 1.06μm, the pulse duration of 20ns, and output energy of 35~40J. The laser was focused on a spot of Ф5mm. Firstly, the profiles of shocked regions of samples were measured by Taylor Hobson admeasuring apparatus, in which two different confinement mediums are used by LSP. Secondly, the ruinous behavior of the free confinement overlays induced by laser shock wave is observed and analyzed. Analyzed and compared with the experiments results, it is discovered that the effects of LSP are different with using different confinement mediums.

Research on ZnS Buffer Layer by RF Magnetron Sputtering for Cu(In,Ga)Se2 Solar Cells

Nanocrystalline ZnS thin films are prepared on glass substrates under various deposition conditions (radio frequency power, and sputtering pressure) using radio frequency magnetron sputtering at room temperature. Through optimization of deposition process, very thin and uniform ZnS layer was deposited to minimize the light blocking effect in short wavelength region. This paper investigates the influence of ZnS buffer layer by magnetron sputtering,and analyses structure,surface topography,and optical properties of ZnS films by using X-ray diffraction (XRD), UV-spectroscopy measurements and scanning electronic microscope (SEM) analysis techniques. Findings show that the high-quality ZnS thin films with a good crystallinity and optical properties, which is zinc blende cubic structure with a preferred orientation, can be grown by sputtering at 300W and 0.6Pa. The films exhibit the optical transparency as high as 80% in the visible region, and the resultant ZnS thin films have a high crystallinity, low defect concentration and good optical properties with the band gap of 3.50eV.

Experiment and Simulation of TC4 Alloy Rods Subject to Laser Shock Processing

In order to improve the fatigue strength of TC4, Nd:Glass pulse laser was used to impact the surface of cylindrical specimens, X-ray stress analyzer was used to test the residual stress distribution of treated area, the laser shock processing on different ratio (η) between the diameter of specimens and laser spot were simulated with ANSYS at the same time. The numerical simulation results were well agreement with experimental data. The results indicate that the different η mainly affect residual stress distribution along the circumferential direction. Contrarily, it has few effects on longitudinal direction and in-depth direction.

Research on Characteristic Microstructure and Properties of Fe20Ni3Mn Alloy Induced by Laser Shock Processing

Fe20Ni3Mn alloy is treated by LSP. The hardness, residual stress and microstructure in the strengthened zone are studied. The results show that the hardness of the strengthened surface is increased about 15% and the surface compressive residual stress is reached about -469MPa. There exist martensite transformation and dislocation within 1mm depth from the specimen surface. Some martensitic structures have obvious trend of growth in steps. Specially, the twin crystals in martersite induced by LSP have important application.