应力作用下电流退火对钴基非晶薄带的巨磁阻抗效应的影响研究

采用应力作用下的直流电流退火处理Co68.2Fe2.3Mo2Si12.5B15非晶薄带,详细讨论了应力退火前后Co基薄带的巨磁阻抗效应的变化,以及退火时间对巨磁阻抗效应的影响,研究表明：应力作用下的电流退火有利于巨磁阻抗效应的提高,并可以通过控制退火时间控制阻抗与外场变化关系曲线形状。     

The effect of the processing parameters on the fabrication of auxetic polyethylene

Auxetic (negative Poisson's ratio) ultra high molecular weight polyethylene has been fabricated by a novel thermal processing route consisting of three stages-compaction, sintering and extrusion. In this paper, the sintering stage is examined in detail, the processing window investigated and the optimum conditions to produce the microporous microstructure necessary for a negative Poisson's ratio are identified. The effects of varying the processing parameters are also studied.     

The effect of processing parameters on the environmental stability of YBaCuO superconductor

The effect of processing parameters on the environmental stability of YBaCuO superconductor was studied by exposing the pellets to a constant level of relative humidity for periods up to 2000 h. Various annealing treatments and compaction pressures, including hot pressing, were utilized to fabricate the pellets. T _c measurements, Auger electron spectroscopy, energy-dispersive X-ray analysis, scanning electron and optical microscopy were employed to characterize the degradation. Samples coated with a polyimide material were also included in the study to determine its utility as a moisture barrier. Results indicated that a slow anneal (41 h) in flowing oxygen produces samples that are far more stable compared to the ones annealed rapidly (9 h) in air. The pellet compaction pressure does not appear to significantly affect the degradation characteristics of the material. The hot-pressed samples showed considerable degradation within 800 h of exposure. The polyimide was found to be ineffective in inhibiting the attack of the humid environment.     

GMAW焊接熔池的流场及其对熔池形状的影响

采用数值分析方法研究了ＧＭＡＷ焊接熔滴状,射流过渡时焊接池的流场,分析了流场对熔池形状的影响。实验表明,焊缝尺寸的计算值和实测值吻合良好,建立的数值分析模型可精确地模拟ＧＭＡＷ焊接熔池的流场,这对控制焊接成形,提高焊接质量具有重要意义。     

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co₆₉Fe_4.5Al_1.5Si₁₀B₁₅ amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.     

The effect of processing parameters on the mechanical properties of auxetic polymeric fibers

Auxetic polymeric fibers have been produced using a melt-spinning technique. The effect of the processing parameters on the fibers has been examined. It was found that the auxetic effect occurs over a very tight temperature window with screw speed, take-off speed and die geometry affecting homogeneity and auxeticity. This is an important finding as it provides a method of producing more homogeneous auxetic fibers with tailored values of Poisson’s ratio.     

Substrate geometry effect on the uniformity of amorphous carbon films deposited by unbalanced magnetron sputtering

A chromium doped amorphous carbon (a-C) film was deposited by an unbalanced magnetron sputtering. A special designed double-V shaped stainless steel model in simulating a plastic injection mold gateway was used as the substrate to investigate the geometric effect on the uniformity of the film. It was found that, on both the side wall and bottom plane of the double-V shaped substrate, the film properties strongly depended on a geometric parameter, geometric aspect ratio, defined as the depth over width of the simulated gateway at the points under measurement. With the increase of the aspect ratio, i.e. approaching to the narrow end and/or closer to the bottom plane of the gateway, the film thickness and hardness decreased and the intensity ratio of the Raman sub-bands D over G increased. With the increase of the aspect ratio, the micro hardness of the a-C film decreased far more significantly on the side wall than that on the bottom plane. With increasing working gas pressure, the film thickness decreased consistently, and the hardness uniformity on both the side wall and bottom plane was improved. When the substrate negative bias voltage was changed from −70 to −100 V, the film uniformity (for both the thickness and hardness) was improved on the bottom plane, but degraded on the side wall.     

The effect of processing parameters on the mechanical properties of kenaf fibre plastic composite

This paper investigates the effects that processing parameters, including temperature and speed, have on the mechanical properties of kenaf fibre plastic composite. Kenaf fibre was used to fabricate a composite material along with polypropylene (PP) as a binding material. The composite was manufactured using a newly developed compression moulding machine. Tensile and impact tests were performed on the PP/kenaf composite to characterise its mechanical properties. The tensile properties of PP/kenaf composite increased by 10% after the addition of unidirectional kenaf fibre (UKF). However, its impact properties simultaneously deteriorated. Dynamic mechanical analysis (DMA) was carried out to examine the material properties. Results show that the storage modulus (E′) and loss modulus (E″) increase with the addition of UKF. However, its addition decreases the tan δ amplitude. The fracture surface of PP/kenaf composite was investigated by SEM. The newly invented compression moulding machine illustrates a new trend in processing parameters of long kenaf fibre plastic composite.     

工艺参数对低温燃烧合成钛酸钡粉体的影响

低温燃烧合成(LCS)钛酸钡粉体的工艺是一种能够直接在低温合成四方相纳米钛酸钡粉的方法。在硝酸盐和柠檬酸体系中,以推进剂化学为理论依据,实验得出各反应物间的最佳摩尔配比,考察了前驱体溶液pH值等对反应过程和最终产物的影响。应用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)等对粉体的结构、形貌进行了分析。结果在300℃点火生成晶粒度在100nm左右无杂质相的四方相钛酸钡粉。     

The influences of processing parameters on forming characterizations during laser rapid forming

Laser rapid forming experiments were carried out with 316L stainless steel and nickel-base alloy to investigate the influences of the processing parameters on forming characterizations systematically. It is found that the height of a single cladding layer was very important for fabrication accuracy and forming stability of components of laser rapid forming because it was affected by almost all processing parameters and was quite difficult to precisely control. For the system with lateral powder feeding pattern, the powder injection point was the most important factor to the height control of single layer. The variation of the width of single clad, which was mainly affected by laser power, spot diameter and scanning velocity, was similar to that in laser surface melting. The surface quality was another important characterization for laser rapid forming and was remarkably affected by oxidation and the powder adhesion. In order to improve the surface quality, the flow flux of shielding gas should be 10 l min⁻¹ and the powder stream cannot be injected to the tail part of the melt pool. Based on the investigation, some metal components were fabricated.     

Evolution of the main intermetallic phases in Al-Si-Cu-Mg casting alloys during solution treatment

The effect of the copper content and the processing route in the solution treatment of four Al-Si-Cu-Mg alloys was studied. The solidus temperature of each alloy was obtained through differential scanning calorimetry (DSC) and compared with Thermo-Calc calculations. This temperature was between 509–510°C in all cases. In consequence, three temperatures were chosen for the solution treatment: 480, 490 and 500°C. An alternative two-step solution treatment finishing at 535°C was also adopted for the alloy with the lowest copper content. Solution times up to 24 h were considered. The dissolution of the intermetallic phases was measured using both, metallographic analysis and from the evolution of the DSC peaks. The results from the two methods were in good agreement. Thermo-Calc calculations helped explaining the changes in volume fraction of the main intermetallic phases observed during the solution treatments.     

微量稀土La掺杂对FeCuNbSiB非晶带材压磁性能的影响

采用单辊快淬法成功制备了微量稀土La掺杂的Fe73.5Cu1Nb3Si13.5B9非晶带材,并讨论了测试频率、测试温度和退火温度对带材掺杂La前后的压磁性能影响。研究表明,在相同条件下,与未掺杂La的带材相比,掺杂La后的带材的压磁效应增大,对微应力更敏感,且其热稳定性也增强。当测试频率在1kHz～1MHz内,带材的阻抗变化随着频率的增大而增大。当压应力在0～0.2MPa时,带材的ΔZ值随着压应力的增大而急剧增大,而在0.2～1.2MPa内,则趋于稳定。当测试温度在20～50℃内,带材的ΔZ值随着温度的升高而增大,且掺杂La的带材的温度稳定性得到明显改善,其温度系数αT由1.3×10-3Ω/℃变为2.68×10-4Ω/℃。在对带材进行退火处理后,其压磁性能有着较大的提高。     

The effect of condensation coefficient on the parameters of flow in problems on strong re-condensation

One-dimensional plane, cylindrical, and spherical flows are considered, which arise in the case of strong re-condensation of gas in the limit of small values of Knudsen number. The effect of the value of condensation coefficient α on the flow is considered. The effect of α on the boundaries of the regions of subsonic, mixed, and supersonic flows is investigated. It is demonstrated that the decrease in the ratio of “hot”-to-“cold” surface radii causes a significant decrease in the effect of the difference of α from unity on the pattern of recondensation flow. The effect of polyatomicity of gas is considered.     

The effect of processing parameters in the carbothermal synthesis of titanium diboride powder

The mechanism of the carbothermal method for synthesizing titanium diboride (TiB₂) powder has been studied. Mixtures of TiO₂, H₃BO₃ and carbon were heated in an argon atmosphere at 1000–1600 °C. The effect of the molar ratio and holding time on the phase evolution was studied by X-ray diffraction. The products were also characterized by scanning electron microscopy observations and particle size measurements.For a composition with a molar ratio of TiO₂:H₃BO₃:C = 1:2.4:5 heated for 1 h, the simultaneous presence of TiC and TiB₂ phases at 1100 °C and the transformation of TiO₂ to Ti₂O₃ at 1200 °C and higher confirms that TiB₂ synthesis is based on a TiC formation mechanism, in which TiC may be formed from a reaction between TiO₂ or Ti₂O₃ and carbon. Then TiC may react with liquid B₂O₃ and/or gaseous B₂O₂ to form the TiB₂ phase. The reaction is completed at 1500 °C. Also by increasing the molar ratio of boric acid to 3, the impurities decreased considerably and pressing of the material had an obvious effect on decreasing the impurities, due to an increase of the surface contact of particles, which causes an effective inhibition of boron escape from the reaction chamber. Under these experimental conditions, a relatively narrow size distribution of TiB₂ particles was produced. When the reaction time increased to 1.5–2 h, grain growth of particles occurred. Therefore, a wider distribution of particle size was obtained.     

Experimental investigation of the planar flow casting process: development and free surface characteristics of the solidification puddle

Planar flow casting (PPC) is one of the most promising processes for the manufacture of thin metal sheets and high performance rapidly solidified alloys, but very little experimental information is available about this process. We have therefore developed an experimental installation that enables us to study the dynamic behavior of the PFC solidification puddle. We have in particular used high speed video recordings to analyze casting runs conducted for various values of the most important parameters. The size and shape of the puddle have been quantified, and the effect of variations in flow rate, gap, and wheel speed on the puddle shape has been studied. We have also investigated the dynamics of the development of the puddle immediately after melt ejection. Both digitized results and high speed photographic sequences of solidification puddles are shown and discussed in this article.