L. W Zhang
,
R.S. Wang
,
J. Th.M.De Hosson
,
Y.L. Xia and F. G. Wang 1) The State Key Lab. for Materials Modification by Laser
,
Ion and Electron Beams
,
Dalian University of Technology
,
Dalian 116023
,
China 2) Department of Applied Physics
,
University of Groningen
,
The Netherlands
金属学报(英文版)
A three-dimensional transient heat transfer model for laser transformation hardening process has been developed in this paper. The finite size of the laser treated sample, the surface heat loss of the sample, the latent heat of phase transformation and the temperature dependence of thermal properties of materials were considered. The heat source was considered as a moving Gaussian heat flux with a constant velocity. Three-dimension unequally spatial grid explicit finite difference equations, alternating direction implicit finite difference equations and implicit finite difference equations were deduced respectively. Three programs to calculate the temperature field were developed using Fortran language. The transient temperature fields of C22, 42CrMo, C60 steel samples during laser transformation hardening process were calculated using these programs, and the widths and depths of laser transformation hardening zones were also predicted. C22, 42CrMo, C60 steel samples were treated by CO_2 laser,the widths and depths of laser transformation hardening zones of these samples were also measured experimentally. The calculated widths and depths of laser transformation hardening zones are in good agreement with the experimental results.
关键词:
temperature field
,
null
,
null
材料科学技术（英文）
Changes of surface morphology following XeCl excimer laser irradiation were investigated for three engineering ceramic materials (Al2O3, Al2O3-SiC nanocomposite and Si3N4) Al2O3 and Al2O3-SiC nanocomposite samples exhibit a smooth rapid melt layer on the surface, and the formation of the metastable gamma-Al2O3 was observed. A silicon-rich layer on the surface was formed after laser irradiation of Si3N4. The toughness K-1c of the materials was measured by the indentation fracture method. After laser irradiation, the toughness of Al2O3, Al2O3-SiC nanocomposite and Si3N4 was improved to various degrees: Al2O3-SiC nanocomposite, 60% (max.); Al2O3, 40% (max.); Si3N4, 12% (max.).
关键词:
alumina
Qinyuan ZHANG
,
Zhonghong JIANG
材料科学技术（英文）
Two kinds of new Ormosil xerogels derived from GPTMS (3-glycidyl propyl trimethoxisilane) and TEOS (tetraethoxysilane) or GPTMS and Ti(OBu)4 (tetrabutoxytitanate) were synthesized via the sol-gel method as dye laser host. Their optical properties, microstructure characteristics and surface laser damage thresholds have been reported. The effects of dye matrix combination on the fluorescence emission, slope efficiency, photostability and tunable bandwidth were examined. Laser oscillation was easily achieved near 620 nm with a slope efficiency of 29% from DCM doped SiO2-Ormosil pumped by a frequency-doubled radiation from a Q-switched Nd:YAG laser. The laser wavelength was tunable over 59nm, and the laser output energy had only a 10% reduction after 2.5×104 pulses at a pump repetition rate of 1 Hz and a pump intensity of 1 J/cm2.
关键词:
TAO Zengyi WANG Aihua ZHU Beidi DENG Shijun CHENG Xudong FU Jiangmin Huazhong University of Science and Technology Wuhan
,
430074
,
ChinaWuhan Research Institute of Material Protection
,
Wuhan
,
430000
,
China
材料科学技术（英文）
An alumina coating was developed on mild carbon steel by plasma spraying and then modified by laser remelting.Some characteristics of plasma sprayed ceramic coating before and after laser remelting,such as microstructure,wear resistance, heat shock resistance,hot corrosion property and bond strength,have been investigated in this paper.
关键词:
plasma spraying
,
null
,
null
Transactions of Nonferrous Metals Society of China
Several coatings including RE mere treated by Laser Rapid Solidification Processing (LRSP). The RE content in the melted surface layer and the surface properties modified by RE and laser treatment on steel were studied. The experimental results show that oversaturated RE was dissolved into the steel surface layer and the steel surface treated by combining RE and LRSP has even higher wear resistance and oxidation resistance than that treated by only LRSP.
关键词:
rare earth;laser treatment;surface modification
Weidou ZHU and Haicheng GU(Dept. of Materials Science and Engineering
,
Xi'an Jiaotong University
,
Xi'an
,
710049
,
China)
材料科学技术（英文）
Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.
关键词:
Journal of Solid State Chemistry
A serial of samples in Y2O3-Ga2O3-Tm2O3 pseudo-ternary system are prepared by solid-state chemical reaction method. The range of solid solution in (Y1-xTmx)(3)GaO6 is 0 < x < 0.384. Powder X-ray diffraction shows that the compounds crystallize in Gd3GaO6 (Cmc2(1))-type structure. The solid solubilities of Y3+xGa5-xO12 (x = 0-0.77) and Tm3+xGa5-xO12 (x = 0-0.62) are 37.5-47.11 at% Y2O3, and 37.5-45.26 at% Tm2O3, respectively. PL spectra of Tm-doped Y3GaO6 show that there is a sharp blue emission at similar to 456 nm from the D-1(2) -> F-3(4) transition at room temperatures with two lifetimes (similar to 5 and similar to 15 mu s) and a narrow saturation range of PL intensity for the Tm3+ content from x = 0.005 to 0.03. The sharp emission and long lifetime of (Y1-xTmx)(3)GaO6 indicate that Y3GaO6 is a potential phosphor and laser crystal host material. (c) 2005 Elsevier Inc. All rights reserved.
关键词:
Tm3+ -doped Y3GaO6;Y2O3-Ga2O3-Tm2O3 system;(Y1-xTmx)(3)Ga5O12 solid;solution;luminescence;crystal-structure;luminescence;phosphor;cations;ions;tb3
