材料期刊网

SIMULATION PROCESS IN LASER WELDING Ⅱ

Y. P. Kathuria (Laser X Co. Ltd. Chick - shi Aichi - ken 472 , Japan)

金属学报(英文版)

With the established technique of laser in science and industry, its applications hare become diversified in the automotive welding.Two potential lasers CO2 and Nd - YAG operating in the i. r. region hare been applied in various demains covering different spectrum of welding,ranging from dissimilar matal to aluminium alloy welding.These lasers considered as thermal processing tools offers an advantage of the keyhole welding offered by the electron beam where the energy is transferred from the surface by the keyhole formation. with the incorporation of these lasers as a flexible thermal processing tool,it has become essential to use them optimally through feedback with planning and constructional rules.Based upon the modulation and duty cycle variation,a simulation technique is demonstrated which enable us to estimate the processing results and determine the characterisitcs of the fabricated part. From the giv- en provess parameters such as haer power, focus radius,processing speed /interaction time and materi- al characteristics, one can optimize the welding condition etc. through the simulation process. In the present work the laser simulation process in welding were carried out with Al- alloy A 5052 of various thickness by using a multiwave high power Nd - YAC lasers.The simulated weld conditions resulted in better utility of the lasers with increased efficiency and better quality. The use of simuation method helped in the designing and prediction of welding technology, which reduced the rejection rate as well as the cost of production.

关键词: easer beam welding , null , null , null

Laser surface cladding of ZM5 Mg-base alloy with Al+Y powder

Transactions of Nonferrous Metals Society of China

The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+Y powder. Laser cladding was carried out with a 5 kW continuous wave CO2 laser by melting the preplaced powder mixture of Al and Y. Following laser cladding, the cladding zone was characterized by a detailed microstructural observation and phase analysis. Moreover, the microhardness and element distribution were evaluated in detail. The surface modified layer consists of Mg-17 Al-12 and Al-4 MgY phases, while alpha-Mg and Mg-17 Al-12 in the substrate. The microhardness of the cladding zone was significantly enhanced as high as HV122 - 180 as compared to HV60 - 80 of the substrate region. The maximal hardness about HV224 is in the interface due to the formation of intermetallic Mg-17 Al-12 phase. The microstructure is refined and Mg diffuses into the cladding material which leads to the formation of Mg-17 Al-12.

关键词: laser cladding;ZM5 Mg base alloy;rare earth;Al plus Y powder;microstructure;magnesium;microstructures;behavior

Doping-Induced Metal-Insulator Transition and the Thermal Transport Properties in Ca(3-x)Y(x)Co(4)O(9)

Journal of Physical Chemistry C

We report the electrical, thermal, magnetic, and thermoelectric properties of Y-doped Ca(3)Co(4)O(9) from 300 down to 5 K. The results indicate that with Y doping, the increase of resistivity originates from the decreases of carrier concentration and mobility, while the increase of Seebeck coefficient is caused by the reduction of carrier concentration together with the enhanced electronic correlation. Point-defect scattering, is the dominant thermal transport mechanism in this system. Due to the considerable difference in mass between Y(3+) and Ca(2+), thermal conductivity is observably suppressed by doping. The substitution of Y also disturbs the interlayer ferrimagnetic coupling. The ground state of this System converts front ferrimagnetism to paramagnetism gradually. The alteration of transport properties of Ca(3-x)Y(x)Co(4)O(9) reveals two Crossovers: the transition from Fermi-liquid-like metal to thermally activated semiconductor occuring at x approximate to 0.25, and the transition from thermally activated semiconductor to two-dimensional variable range hopping semiconductor occurring at x approximate to 0.5. The optimal thermoelectric response In Ca(3-x)Y(x)Co(4)O(9) is found to exist only at the critical state after which the doping-induced metal-insulator transition takes place. Oil the basis of these experimental results, a possible phase diagram for Ca(3-x)Y(x)Co(4)O(9) is proposed.

关键词: temperature thermoelectric properties;giant magnetoresistance;solid-solutions;conductivity;electron;system;ca3co4o9+delta;thermopower;crystals;behavior

Study on Laser Transformation Hardening of HT250 by High Speed Axis Flow CO2 Laser

Yunxia YE , Yonghong FU , Yongkang ZHANG

材料科学技术（英）

In this article, laser transformation hardening of HT250 material by high speed axis flow CO2 laser was investigated for first time in China. Appropriate laser hardening parameters, such as laser energy power P(W), laser scanning rate V m/min), were optimized through a number of experiments. The effect of the mentioned parameters on the hardened zone, including its case depth, microhardness distributions etc ., were analyzed. Through the factual experiments, it is proved that axial flow CO2 laser, which commonly outputs low mode laser beam, can also treat materials as long as the treating parameters used are rational. During the experiments, the surface qualities of some specimens treated by some parameters were found to be enhanced, which does not coincide with the former results. Furthermore in the article, the abnormal phenomenon observed in the experiments is discussed. According to the experimental results, the relationship between laser power density q and scanning rate V is shown in a curve and the corresponding formulation, which have been proved to be valuable for choosing the parameters of laser transformation hardening by axial flow CO2 lasers, was also given.

关键词: Laser transformation hardening , null , null , null

WC-x%Co films prepared by arc ion plating

International Journal of Refractory Metals & Hard Materials

WC-x%Co films (x = 0, 4, 15) were obtained by are ion plating (AIP). The deposition rate of the process and the surface microhardness of the films were measured. The microstructure of the films was analyzed by examining cross sections by scanning electron microscopy (SEM). It is demonstrated that the deposition of WC-x%Co films can be obtained by means of the proposed process. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词: coatings

The oxidation of Co-Y binary alloys at 600-800 degrees C in air

Corrosion Science

The oxidation of pure Co and two Co-Y alloys containing 2 at.% and 5 at.% Y has been studied at 600-800 degrees C in air. The oxidation of pure cobalt at all temperatures followed the parabolic rate law. The oxidation of the two alloys approximately followed the parabolic rate law at 800 degrees C, but was closer to cubic behavior at 600 and 700 degrees C except Co-5Y at 600 degrees C, which deviated from the cubic and parabolic rate law. The corrosion of both alloys at the three temperatures produced an external scale containing Co oxides (Co3O4, CoO) and Y2O3 and an internal oxidation region where Co17Y2 was converted into Co and Y2O3. The distribution of Y2O3 closely followed that of the intermetallic compound (Co17Y2) in the original alloy. The corrosion mechanism of the alloys is examined. (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词: Co;Y;oxidation;high-temperature oxidation;possible scaling modes;internal oxidation;oxidant pressures;h-2-h2s mixtures;sulfidation;oxygen

Magnetic, electronic transport and magneto-transport behaviours of (Co1-xMnx)(2)P compounds

Journal of Physics D-Applied Physics

Magnetic, electronic transport and magneto-transport behaviours of (Co1-xMnx)(2)P (0.55 <= x <= 0.675) compounds have been systematically investigated. A typical metallic-conductivity behaviour is observed in the ferromagnetic compound (Co0.45Mn0.55)(2)P. The increase in the Mn concentration gives rise to dramatic changes in magnetic, electronic transport and magneto-transport behaviours. With increasing temperature, a first-order phase transition from antiferromagnetism to ferromagnetism takes place at about 145 K, 185K and 240K for x = 0.60, 0.625 and 0.65, respectively. (Co0.4Mn0.6)(2)P and (Co0.375Mn0.625)(2)P compounds experience a metal-insulator transition (Anderson transition) with decreasing temperature. An external magnetic field of 5 T strongly influences the Anderson transition, lowering the transition temperature from 80 to 55K for (Co0.4Mn0.6)(2)P and from 115 to 70K for (Co0.375Mn0.625)(2)P. In contrast with this metal-insulator transition, an insulating behaviour appears in the temperature range from 10 to 300K for (Co0.35Mn0.65)(2)P and (Co0.325Mn0.675)(2)P compounds. Below the antiferromagnetic-ferromagnetic transition temperature TAF-F, a metamagnetic transition can be induced by an external magnetic field. The metamagnetic transition is accompanied by a maximum magnetoresistance ratio of -7%, -6.3% or -3.7% at 5 T in the (Co0.4Mn0.6)(2)P, (Co0.375Mn0.625)(2)P or (Co0.35Mn0.65)(2)P compound at 10 K. The mechanisms of magnetoresistive behaviours are discussed in terms of the formation of a super-zone gap in the antiferromagnetic state.

关键词: metamagnetic-transition;solid solutions;resistivity;systems;magnetoresistance;anomalies;alloys;field

Co-precipitation synthesis and photoluminescence properties of (Ca(1-x-y),Ln(y))MoO(4): xEu(3+) (Ln = Y, Gd) red phosphors

Journal of Alloys and Compounds

(Ca(1-x-y),Ln(y))MoO(4): xEu(3+) (Ln = Y, Gd) red phosphors were prepared by co-precipitation method with NH(4)HCO(3)-NH(3)center dot H(2)O system as the precipitating agent. X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), and energy-dispersive X-ray spectrometer (EDS) were used to characterize the structure and composition of the phosphors. The synthesized (Ca(1-x-y),Ln(y))MoO(4): xEu(3+) have scheelite structure with pure phase. FT-IR spectra show strong absorption peaks between 914 and 730 cm(-1) which are assigned to the vibration of O-Mo-O in MoO(4)(2-) tetrahedron. The EDS analysis reveals that the red phosphors have been successfully prepared by co-precipitation method according to theoretic ratio. Photoluminescence spectra show a red emission around 614 with 394 and 464 nm excitation, which is match well with the output wavelength of commercial ultraviolet and blue LED chips. The luminescent intensity of (Ca,Ln)MoO(4): Eu(3+) is obviously higher than that of CaMoO(4): xEu(3+). Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

关键词: Co-precipitation;Red phosphor;Photoluminescence;(Ca(1-x-y),Ln(y))MoO(4): xEu(3+) (Ln = Y Gd);hydrothermal synthesis;camoo4;eu3+;luminescence

Magnetocaloric effect and size-effect related thermal hysteresis reduction in MnAs(1-x)P(x) compounds

Physica Status Solidi a-Applications and Materials Science

In MnAs(1-x)P(x) compounds (x = 0.006 and 0.01), prepared by mechanical alloying, the thermal hysteresis is greatly reduced from about 10-30K in MnAs-based compounds, prepared by conventional melting, to 2K for x = 0.01 (or 4K for x = 0.006). Such obvious hysteretic reduction is ascribed to the grain-size effect, largely due to the preparation method of mechanical alloying. Meanwhile, a maximum value of the magnetic-entropy change Delta S(M) of 11.3 J/kgK for a field change of 2 T is obtained at 294.5K for MnAs(0.994)P(0.006). The study on the MnAs(1-x)P(x) system and also the effect of the preparation technology may be beneficial for the realization of magnetic refrigerants for application at room temperature. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词: magnetocaloric effect;mechanical alloying;thermal hysteresis;gd-5(si2ge2);transition;mnas

Si和Co含量对快淬LaFe13-x-y SixCoy合金凝固行为的影响

董中奇 , 涂赣峰

材料与冶金学报 doi:10.3969/j.issn.1671-6620.2008.04.014

采用熔体快淬的方法研究了Si,Co含量对LaFe13-x-ySixCoy合金凝固行为的影响.应用XRD和SEM分析了合金显微组织、结构和相组成.结果表明:Si,Co含量对合金的凝固行为有很大的影响,当合金中x=O,Y=0-0.4时合金显微组织由α-Fe相和La+α-Fe相组成;当x=0.5～1.0,Y=0～0.4时合金显微组织由α-Fe相和La(Fe,Co)Si相组成;当x=1.0,y=0.6时合金显微组织中出现La(Fe,Co,Si)13相.

关键词: 稀土 , 熔体快淬 , IaFe13-x-y合金 , 凝固行为