Advanced Materials Research Vol. 629

Abstract: The influence of heat treatment on damping capacity of (Fe₈₃Ga₁₇)_99.5B_0.5 wires was investigated using a computer-controlled automatic inverted torsion pendulum. The measurements have been carried out as a function of strain amplitude in free-decay mode. The microstructures of (Fe₈₃Ga₁₇)_99.5B_0.5 wires were also investigated to clarify the effects of heat treatment on the damping capacity. The results show that the annealing temperature affects the damping capacity of (Fe₈₃Ga₁₇)_99.5B_0.5 wires by varying the grain size. With increasing annealing temperature, the damping capacity is enhanced and becomes more sensitive to strain amplitude. There is no obvious difference in the structure of (Fe₈₃Ga₁₇)_99.5B_0.5 wires with different cooling rate which indeed affects the damping properties. Large cooling rate will help to get higher damping capacity. The Fe-Ga alloys show certain damping capacity and are worth paying close attention to enhance this property so as to get access to the field of unwanted noise and vibration reduction applications.

Abstract: The new technology of superalloy vacuum-electromagnetic casting was developed and the feeding mathematical model melt in vacuum-electromagnetic casting was established. The availability of mathematical model was approved by the experiments of the IN100 superalloy. The experimental results indicate that the feeding capacity of melt in vacuum casting can be greatly increased by imposing the 50Hz, 60A rotating electromagnetic stirring, which can decrease the central shrinkage cavity in superalloy ingots, so the quality of the superalloy ingots can be wide-range improved.

Abstract: In order to achieve high quality superalloy ingots, an investigation of applying linear electromagnetic stirring to the superalloy vacuum casting solidifying process has been put into effect with electroprobe microanalysis and optical microscope. The results indicate that an one sided, upward linear electromagnetic stirring with 50Hz frequency and 140A current can effectively refine the isometric crystals and shorten the ratio of central shrinkage cavity in superalloy ingots.

Abstract: Increases in the penetration depth of laser welding has gained undoubted interest, especially in the aerospace, power station, ship building, and other heavy industries. Gas-jet-assisted keyhole laser welding is a prospective method for improving the penetration of conventional laser welding. A series of experiments using this method were conducted with different parameters of the assisted gas jet and the welding speed. The microstructures of weld joints were observed using optical microscopy, and microhardness was also measured. The investigation results showed that the penetration depth of this laser welding increased by more than 20%, with a maximum increase of approximately 26%, at different welding speeds, while the weld width was significantly reduced compared with that of conventional laser welding. The key factor affecting the penetration increase is the interaction between the assisted gas jet and the plasma. The penetration increase was determined by the distribution and amplitude of the assisted gas jet at the position of the keyhole orifice. The grain in the heat-affected zone (HAZ) and weld seam of gas-jet-assisted keyhole laser welding was finer, and the number of columnar grains was also significantly reduced. The microhardness of the HAZ for the assisted gas jet was much lower, and more pearlite and less martensite were observed this zone. This was caused by the reduced maximum temperature of the molten pool, reduced high-temperature residence time, increased cooling rate, and diminished temperature gradient with the introduction of the assisted gas jet.

Abstract: Resonant pattern in ellipsoidal microwave cavities were analyzed systematically in this article. Electric field distribution in cavities with different sizes was calculated by the finite difference time-domain method (FDTD). The results of the simulation show that, the microwave fed in though antenna, two different transmission patterns be formed in the microwave cavities, when the R and Z were properly chosen．In the first case, only one strong electric field area was formed at the bottom of the ellipsoidal cavity. For the second case, two main strong electric-field areas around the focal points, resonant series “TM_0mn” mode were also found, the size of ellipsoid resonant cavities reveals obvious regularity in the resonant series, the electric-field shape of a resonant mode is similar with each other except that the intensity of the two main strong electric-field areas. In the same resonant mode, z has a good linear correlation with r. the research results of the ellipsoidal microwave cavities with two main strong electric-field areas will provide more choices for design new plasma reactors.

Abstract: Thermal–mechanical treatment is widely utilized by steelmakers to optimize the properties of high–strength cold drawing eutectoid steel wires. This paper presents the influence of industrial thermal–mechanical treatment utilized in practical manufacturing on microstructure and mechanical properties of drawn pearlitic steels. After post thermal–mechanical processing, drawn pearlitic steel features lower residual stress and improved yield/ultimate tensile strengths, and exhibits a more perfect fiber texture characteristic. Nevertheless, the torsion test of treated steel wire demonstrates that delamination occurs during torsional deformation, which implicates that the studied thermal–mechanical treatment is whereas not the optimum process for manufacturing the high–performance steel wires. The sequential TEM observation shows the remarkable different structure of pearlite lamellae in drawn and treated wires. The local stress concentration resulting from the separately granular cementite precipitation may attribute to the delamination of steel wire after post drawing.

Abstract: Three groups of commercial 1050 Al alloy were subjected to equal channel angular pressing (ECAP) at room temperature using route A, route C and route Bc, respectively. Mechanical properties and fracture modes of as-annealed and ECAPed samples were investigated. The microhardness of 1050 Al fabricated by ECAP increases by a factor of about 1.5 compared to the as-annealed state. The ultimate tensile strength (UTS) increases significantly after ECAP, while the elongation decreases. But they are strongly dependence on the number of ECAP passes and the pressing route. The UTS and elongation of the samples processed by route Bc are best, consequently, the static toughness U of the samples is enhanced. Besides, all specimens subjected to ECAP deformation failed in a ductile manner.

Abstract: In this paper, the initial residual stress field for titanium alloy monolithic component blank is simulated and analyzed by applying a sequentially coupled thermal and mechanical procedure based on finite element method. The control equation of heat conduction of annealing process is studied, and the boundary condition and fundamental equations of simulation are given. The research results show that the initial residual stress field for titanium alloy monolithic component blank radiates from the center region to outside, the center region being the maximum value, then decreases gradually, until a minimum value is attained at the corner.

Abstract: InP/In_0.82Ga_0.18As/InP heterostructure used for infrared detector were grown on (100) S-doped InP substrates using two-step growth technique by low temperature metal-organic chemical vapor deposition. The growth was performed using TMIn, TMGa, AsH₃, and PH₃ as growth precursors in a horizontal reactor. The substrates on a graphite susceptor were heated by inductively coupling RF power, their temperatures were detected by a thermocouple, and the reactor pressure was kept at 10000 Pa. The growth structure of detector included In_0.82Ga_0.18As buffer with the thickness of 100 nm, In0.82Ga0.18As absorption layer with the thickness of 2.8 μm, and the InP cap with the thickness of 0.8 μm. The planar type of p-i-n detector was fabricated by Zn diffusion. The properties of In_0.82Ga_0.18As detector were studied, the curves of the I-V characteristics, the range of response spectrum, and the detectivity (D*) were obtained.

Abstract: Conducting ring is an electric transmission device to achieve current, video, data signal and power transmission between two relatively slewing mechanism, so it has been widely used in all kinds of precision turntable and inertial navigation equipment. The slip ring and brush wire of conducting ring are connected to other equipment by copper wire or copper transfer metal plates. Currently, Eutectic 63Sn-37Pb solder and electric iron manual welding are often used. But for gold alloy, when SnPb solder is used, gold element will dissolve in solder because Au dissolves in Sn easily, and brittleness intermetallic was produced at the interface during cooling, which embrittled the joint. This paper analyzed the solderability of gold alloy and copper, summed up the research status of soldering technology of gold alloy and copper in China and abroad. It pointed out that it is necessary and urgent to develop soldering technology of gold alloy with copper.