Q. Y Pan
,
WD. Huang
,
YM. Li
,
X. Lin
,
YH. Zhou and X.C. Yan( State Key Lab. of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China ( Laser Processing Center
,
Tianjin College of Textile Technology
,
Tianjin 300160
,
China )
金属学报(英文版)
A novel wide-band laser cladding system, with high rate of cladding, has been developed in the present work. The system mainly consisted of a 5kW CO2 laser, an automatic Fowder feeder and a wide-band scanning rotative polygon mirmr which can produce a linear or rectangular focused laser beam. Using this system, a Ni-Cr-Si-B alloy powder was cladded on the sudece of tgpe 321 austenitic stainless steel in onder to improve its wear and cormsion resistance. The pitting cormsion, high temperuture oxidation and wear tests were conducted in onder to evaluate the propertles of the laser cladded layer. The results demonstrated that the cladded layer can significantly improtte the adhesive wear and pitting cormsion resistance of the substmte. Moreover,the cladded layer exhibited good oxidafion resistance, which is almost the same as that of GMR-235D N-based superalloy.
关键词:
austenitic stainless steel
,
null
,
null
,
null
郑树起
,
闵光辉
,
邹增大
,
王效志
,
韩建德
金属学报
系统研究了利用La2O3和B4C粉制备LaB6粉末的反应合成工艺.La2O3-B4C系反应热力学分析表明反应产物的气体分压对LaB6的形成有重要影响,减小气体分压可以明显降低LaB6的合成温度,结合DTA测定结果,确定了LaB6粉末的合成温度.利用X射线衍射分析了不同温度和保温时间条件下所生成粉末的相组成,并分别用扫描电镜和化学分析方法分析了所生成LaB6粉末的颗粒尺寸、形貌及纯度.实验结果表明,La2O3-B4C系制备LaB6粉末的优化工艺是真空度133 Pa,1673 K保温2.5 h,所合成的LaB6粉末颗粒比较规整,大多呈近似圆球形,平均直径3μm,纯度达98.2%.
关键词:
La2O3
,
null
,
null
,
null
,
null
郑树起
,
闵光辉
,
邹增大
,
王效志
,
韩建德
金属学报
doi:10.3321/j.issn:0412-1961.2001.04.018
系统研究了利用La2O3和B4C粉制备LaB6粉末的反应合成工艺.La2O3-B4C系反应热力学分析表明反应产物的气体分压对LaB6的形成有重要影响,减小气体分压可以明显降低LaB6的合成温度,结合DTA测定结果,确定了LaB6粉末的合成温度.利用X射线衍射分析了不同温度和保温时间条件下所生成粉末的相组成,并分别用扫描电镜和化学分析方法分析了所生成LaB6粉末的颗粒尺寸、形貌及纯度.实验结果表明,La2O3-B4C系制备LaB6粉末的优化工艺是真空度133 Pa,1673 K保温2.5 h,所合成的LaB6粉末颗粒比较规整,大多呈近似圆球形,平均直径3μm,纯度达98.2%.
关键词:
La2O3
,
B4C
,
反应
,
合成
,
LaB6
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
The microstructural evolution during solidification and subsequent solid-state transformation of AISI 304 stainless steel is studied by directional solidification and quenching methods in this paper. The phase transformation sequence in the steel directionally solidified is that the precipitation of primary ferritic dendrites, ferrite-austenite eutectic reaction, and the direct formation of austenite occur in sequence during the directional solidification of the austenitic stainless steel. At the eutectic reaction stage, plenty of columnar and cellular eutectic colonies composed of the coupled growth of lamellar ferrite and austenite take place. During the course of subsequent solid-state transformation, austenite grows into ferrite gradually, resulting in the disappearing of eutectic colonies and thinning of primary ferritic dendrites, and dendrite cores of primary ferrite are retained as the final skeletal ferrite in the final microstructure. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
austenitic stainless steel;directional solidification;eutectic colony;austenitic stainless-steel;cr-ni alloys;sequence;welds
D.Q.Tang
,
Y. Wang
,
E.Y.Jiang
,
C.Zhao and F.L.Sun Department of Applied Physics
,
Tianjin University
,
Tianjin 300072
,
China
金属学报(英文版)
CN x films were made by a facing targets sputtering ( FTS) systemon the Si(100) substrate under different N 2 partial pressure. XRD, XPS, FTIR and Raman Spectroscopy( RS) were measured to investigate the structure and the binding state of the film. The films are amorphous and the N/C increases with the N 2 partial pressure increasing and reaches 0 46 when the N 2 pressure is 100%. The N incorporated C forms N sp 2C and N sp 3C mainly and there is a small amount of C≡N.
关键词:
Wenjing Yao
材料科学技术（英文）
The liquid-solid transitions of (Co2Si+CoSi) and (CoSi+CoSi2) eutectic alloys were realized in drop tube and the rapid eutectic growth mechanism of intermetallic compounds was examined. The experimental and calculated results indicate that with increasing Co content, the intermetallic compound prefers nucleating primarily. The eutectic microstructures experience the transitions of `lamellar-anomalous-divorced' eutectic with undercooling. In undercooled state, the growth of CoSi intermetallic compound always lags behind others, and no matter how large the undercooling is, this intermetallic compound grows under the solutal diffusion control. The calculated coupled zone demonstrates that (Co2Si+CoSi) eutectic can form within certain undercooling regime, when the composition is in the range from 23.6% to 25.4% Si. And the calculated coupled zone of (CoSi+CoSi2) covers a composition range from 40.8% to 43.8% Si.
关键词:
Liquid-solid transition
Journal of Alloys and Compounds
La1-xSrxCrO3 (x=0.0 similar to 0.5) samples were prepared by the sol-gel method. The crystal structures of La1-xSrxCrO3 at room temperature all are of the othorhombic perovskite GdFeO3-type. XPS analysis indicates that chromium ions are in mixed valence state. The introduction of Sr2+ into the lattice is compensated by the oxidation from Cr3+ to Cr6+ With x increasing, the amount of Cr6+ increases. The presence of the Cr6- is one of the key factors that affect the electric conductivity of La1-xSrxCrO3. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
rare earth;perovskite La1-xSrxCrO3;high-temperature conductivity;interconnector;XPS
Journal of Applied Physics
The structure and transport properties of Sm1-xCaxMnO3 with 0.4less than or equal toxless than or equal to0.8 were investigated. With decreasing temperature from 350 K, cooperative Jahn-Teller (JT) distortion develops, leading to the formation of a charge ordered (CO) state and anomalies in the lattice parameters and resistivities. At low temperature the magnetoresistance effect originates from the polarization of the localized t(2g) spins under the magnetic field and decreases with the increase in Ca2+ content x, whereas the stability of the CO state at the CO transition temperature T-CO strongly depends on both Ca2+ content and cooperative JT distortion. These interesting phenomena sufficiently confirm the close relationship among charge, lattice, spin, and orbital degrees of freedom. (C) 2004 American Institute of Physics.
关键词:
metal-insulator-transition;magnetic phase-diagrams;double exchange;manganites;field;magnetoresistance;la1-xcaxmno3;diffraction;bandwidth;x=0.25
Applied Physics a-Materials Science & Processing
The Seebeck coefficient is a function of carrier concentration and configurational entropy. In this report, we semi-theoretically investigate the Seebeck coefficient of Ln (x) Ca(1-x) MnO(3) (Ln=Rare-earth) perovskites based on the electronic structure of the 3d orbitals of Mn ions, using the developed Heikes model, Boltzmann transport model, and diffusion model. The results show that the Seebeck coefficient of such a strongly correlated electron system in paramagnetic state is remarkably affected by site degeneracy. As temperature decreases, the evolution of the spin and orbital degrees of freedom together with the change in phonon scattering mode describes the Seebeck coefficient behavior satisfactorily. The phonon drag effect at low temperature is also discussed.
关键词:
high-temperature;thermoelectric-power;thermal-conductivity;transport-properties;single-crystals;electron;thermopower;manganites;oxide;heat
