Electron Beam Deflection When Welding Dissimilar Metals

1990 ◽  
Vol 112 (3) ◽  
pp. 714-720 ◽  
Author(s):  
P. S. Wei ◽  
T. W. Lii
Keyword(s):  
Electron Beam ◽  
Incident Angle ◽  
Electrical Contact ◽  
Beam Deflection ◽  
Beam Power ◽  
Dissimilar Metals ◽  
Electrical Contact Resistance ◽  
Energy Beam ◽  
Relative Magnetic Permeability ◽  
The Difference

High-intensity electron beam deflection due to thermoelectric magnetism generated during the welding of dissimilar metals is systematically and analytically investigated. A simple thermoelectric model is proposed and the temperature field, penetration depth of the fusion zone, magnetic field, and motion of an electron are determined. Deviation of the fused zone from a joint is affected by the incident angle of the energy beam, the difference in Seebeck coefficients of workpieces, relative magnetic permeability, beam power, welding speed, thermal and electrical conductivities, and the effective electrical contact resistance. Their effects are clearly interpreted in this study. Analytical results for the deviation of the fused zone from the joint between the materials to be welded show good agreement with available experimental data.

Three-Dimensional Electron-Beam Deflection and Missed Joint in Welding Dissimilar Metals

1997 ◽  
Vol 119 (4) ◽  
pp. 832-839 ◽  
Author(s):  
P. S. Wei ◽  
F. K. Chung
Keyword(s):  
Electron Beam ◽  
Electrical Contact ◽  
Three Dimensional ◽  
Electron Gun ◽  
Beam Deflection ◽  
Beam Power ◽  
Dissimilar Metals ◽  
Electrical Contact Resistance ◽  
Paraboloid Of Revolution

Three-dimensional deflection of the electron beam resulting in a missed joint due to thermoelectric magnetism generated while welding dissimilar metals is systematically investigated. The incident energy rate distribution is assumed to be Gaussian and the deep and narrow welding cavity induced is idealized as a paraboloid of revolution. With a three-dimensional analytical solution for the temperature and by solving Maxwell’s electromagnetic equations, thermoelectric currents, magnetic flux densities, and deflections of the beam are found. The predictions agree with available experimental data. The results find that missed joints can be reduced by increasing the dimensionless accelerating voltage-to-Seebeck e.m.f. parameter, Peclet number, and effective electrical contact resistance parameter, and decreasing dimensionless beam power, magnetic permeabilities, and electrical conductivity ratio between metals 1 and 2. Tilting workpieces and shifting the electron gun from the joint line are also feasible. A three-dimensional analysis is required for a successful determination of beam deflection.

Fusion Zone Shapes in Electron-Beam Welding Dissimilar Metals

2000 ◽  
Vol 122 (3) ◽  
pp. 626-631 ◽  
Author(s):  
P. S. Wei ◽  
Y. K. Kuo ◽  
J. S. Ku
Keyword(s):  
Electron Beam ◽  
Fusion Zone ◽  
Electron Beam Welding ◽  
Beam Power ◽  
Strong Mixing ◽  
Width Ratio ◽  
Dissimilar Metals ◽  
Measured Concentration ◽  
Joint Plane ◽  
The Difference

Experiments on welding dissimilar metals, such as aluminum or copper to iron with an electron-beam welder, are conducted. It is found that the observed depth-to-width ratio of the fusion zone in aluminum can be greater than unity while that in iron is around unity. The former is attributed to the formation of a cavity resulting from a high vapor pressure. The difference in depths increases with beam power. The observed depth-to-width ratios of fusion zones in welding copper to iron can be greater than unity. A unique maximum depth is near the joint plane, as a result of strong convective mixing and high incident flux, even though the melting temperatures are different. Strong mixing is confirmed by measured concentration profiles across the fusion zones of dissimilar metals. To a first approximation fusion zone depths with depth-to-width ratios greater than or identical to unity are determined from scale analyses of heat conduction equations in welding the same metals with a high and low-power-density beam, respectively. The propositions are verified by experimental results. [S0022-1481(00)00103-1]

3-D Observation of Cu Particles Precipitated in Si by High-Angle Hollow-Cone Dark-Field Transmission Electron Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 479-480
Author(s):  
Hiroshi Kakibayashi ◽  
Kuniyasu Nakamura ◽  
Ruriko Tsuneta
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Incident Angle ◽  
Random Access ◽  
Dark Field ◽  
Beam Deflection ◽  
High Angle ◽  
Hollow Cone ◽  
Transmission Electron

The performance of electronic devices, such as dynamic random access memories, is degraded by contamination due to impurity atoms as well as crystalline imperfections created during processing. The evaluation of those degradation causes is generally done using an analytical transmission electron microscope. The information obtained, however, is limited to two-dimensional images of the specimen as seen from a single direction. Advanced semiconductor devices with finer-pattern structures are expected to exhibit larger fluctuations in device performance due to the spatial distribution of the faults. A new method has thus been examined to determine the atomic species and to reconstruct three-dimensional (3-D) images of the specimen structure by using high-angle hollow-cone dark-field transmission electron microscopy (HADF-TEM).A incident angle controller was added to a conventional TEM to control the electron-beam deflection coils. This enables the incident electron beam to be inclined and rotated, providing hollow-cone illumination of the specimen, as shown in Fig. 1.

The Impact of Charging on Low-Energy Electron Beam Lithography

2004 ◽  
Vol 10 (6) ◽  
pp. 804-809 ◽  
Author(s):  
Lau Kien Mun ◽  
Dominique Drouin ◽  
Eric Lavallée ◽  
Jacques Beauvais
Keyword(s):  
Electron Beam ◽  
Electron Beam Lithography ◽  
Low Voltage ◽  
Beam Deflection ◽  
Time Interval ◽  
Direct Write ◽  
Energy Beam ◽  
Surface Charging ◽  
Adjacent Structures ◽  
The Impact

A major issue in low voltage lithography is surface charging, which results in beam deflection presented as uneven exposure between adjacent structures. In this study, charge-induced pattern distortions in low-voltage energy beam lithography (LVEBL) were investigated using a silicide direct-write electron beam lithography process. Two methodologies have been proposed to avert charging effects in LVEBL, namely, pattern randomizing and lithography using the crossover voltage. Experimental results demonstrated that these methods are effective in significantly reducing the problems associated with charging. They indicate that charging on a sample is a function of time interval and proximity between line structures. In addition, the optimum time and distance between exposures for no charge-induced pattern distortion were determined. By using the crossover voltage of the material for lithography, charging effect can be significantly minimized.

The Interplay of Nanocontact and Electrical Properties of ZnO and InP Nanowires and Polyaniline Nanofibers

2009 ◽  
Vol 1198 ◽  
Author(s):  
Yen-Fu Lin ◽  
Wen-Bin Jian
Keyword(s):  
Electron Beam ◽  
Electrical Properties ◽  
Contact Resistance ◽  
Ohmic Contacts ◽  
Electrical Contact ◽  
Schottky Contacts ◽  
Specific Contact Resistance ◽  
Electrical Contact Resistance ◽  
Polyaniline Nanofibers ◽  
Current Voltage

AbstractThe interface problems in nanomaterial based electronics play important roles. We have learned that the nanocontact, due to its reduced contact area, could give a high electrical contact resistance and a nonlinear current-voltage behavior though the specific contact resistance is in the same order of magnitude as that of macroscopic contacts. Through the current-voltage and temperature behaviors, the nanocontact properties could be categorized into Ohmic and Schottky types. The electrical properties of the nanowire based two-probe devices could be rationalized as two Ohmic contacts, one Ohmic and one Schottky contacts, and two back-to-back Schottky contacts. Moreover, the nanocontact could be treated as a one-dimensional disordered electron system for further studies. After the intrinsic nanowire and contact resistances are separated from each other, the electron transport and the carrier concentration of native doping in ZnO and InP nanowires can be determined. The nanowires are determined to have low carrier concentrations, implying a high sensitivity to light and gas. The contact and nanowire dominated two-probe devices are exposed to light and gas to identify the contact effects. In addition to the inorganic nanowires, the organic nanomaterials, the HCl-doped polyaniline nanofibers, can be analyzed by using the same approach. The dielectrophoresis technique is implemented to position nanofibers into an electron-beam lithographically patterned nanogap. To shine the electron-beam on contact areas, the organic/inorganic nanocontact resistance is reduced so as to probe the intrinsic electrical property of a single polyaniline nanofiber.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

1990 ◽  
Vol 48 (1) ◽  
pp. 198-199
Author(s):  
Ryo Iiyoshi ◽  
Susumu Maruse ◽  
Hideo Takematsu
Keyword(s):  
Electron Beam ◽  
Tungsten Wire ◽  
Local Heating ◽  
Electron Gun ◽  
Original Position ◽  
Beam Power ◽  
Radius Of Curvature ◽  
High Brightness ◽  
Beam Focusing ◽  
Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

scholarly journals Influence of Beam Power on Young’s Modulus and Friction Coefficient of Ti–Ta Alloys Formed by Electron-Beam Surface Alloying

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1246
Author(s):  
Stefan Valkov ◽  
Dimitar Dechev ◽  
Nikolay Ivanov ◽  
Ruslan Bezdushnyi ◽  
Maria Ormanova ◽  
...  
Keyword(s):  
Electron Beam ◽  
Young’S Modulus ◽  
Coefficient Of Friction ◽  
Young's Modulus ◽  
Beam Power ◽  
Surface Alloying ◽  
Surface Alloys ◽  
X Ray ◽  
The Coefficient Of Friction ◽  
Beam Surface

In this study, we present the results of Young’s modulus and coefficient of friction (COF) of Ti–Ta surface alloys formed by electron-beam surface alloying by a scanning electron beam. Ta films were deposited on the top of Ti substrates, and the specimens were then electron-beam surface alloyed, where the beam power was varied from 750 to 1750 W. The structure of the samples was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Young’s modulus was studied by a nanoindentation test. The coefficient of friction was studied by a micromechanical wear experiment. It was found that at 750 W, the Ta film remained undissolved on the top of the Ti, and no alloyed zone was observed. By an increase in the beam power to 1250 and 1750 W, a distinguished alloyed zone is formed, where it is much thicker in the case of 1750 W. The structure of the obtained surface alloys is in the form of double-phase α’and β. In both surface alloys formed by a beam power of 1250 and 1750 W, respectively, Young’s modulus decreases about two times due to different reasons: in the case of alloying by 1250 W, the observed drop is attributed to the larger amount of the β phase, while at 1750 W is it due to the weaker binding forces between the atoms. The results obtained for the COF show that the formation of the Ti–Ta surface alloy on the top of Ti substrate leads to a decrease in the coefficient of friction, where the effect is more pronounced in the case of the formation of Ti–Ta surface alloys by a beam power of 1250 W.

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