铝氧比对含铝炸药水下爆炸载荷及能量输出结构的影响

为了系统地研究铝氧比对含铝炸药水下爆炸载荷及能量输出结构的影响,在验证数值模型有效性的基础上,针对铝氧比分别为0、0.16、0.36、0.63的RDX基含铝炸药,利用耦合欧拉-拉格朗日方法模拟了其水下爆炸连续的全过程,考虑了冲击波载荷和气泡载荷之间的耦合作用,从冲击波、气泡和能量输出结构三方面对影响效应进行评估。计算结果表明:随着铝氧比的增大,含铝炸药水下爆炸冲击波衰减时间常数、冲击波冲量、气泡脉动周期、气泡最大半径以及比气泡能都增大;铝氧比为0.36时,冲击波峰值压力、冲击波能流密度和比冲击波能达到最大。铝粉的加入对气泡能的提高相对于冲击波能更加显著。     

RDX基含铝炸药在混凝土中爆炸的实验研究

为了研究含铝炸药在混凝土介质中的毁伤效果,对不同含铝量的3种炸药进行了70g药量小尺寸混凝土爆炸实验,重点研究了铝粉含量和炸药埋深对毁伤效应的影响,利用高速摄影机拍摄了混凝土靶毁伤过程。结果表明:炸药埋深对炸药的毁伤效果有着重要的影响,埋深为30cm时的毁伤效果要远大于10cm时,当炸药的埋深为10cm时含铝量为15%的炸药毁伤效果最佳;铝粉含量越高,火光面积越大,持续的时间越长。     

含铝炸药水下爆炸性能的实验研究

对RS211、HL-1、HL-2这3种含铝炸药和TNT炸药进行了水下爆炸实验,测量了4种炸药水下爆炸冲击波压力剖面和气泡脉动周期,获得了4种炸药水下爆炸冲击波的峰值超压、冲量、能量和气泡能。实验结果表明,在所研究的范围内,与TNT炸药相比,含铝炸药的冲击波能量有明显增加,约为TNT炸药的1.20～1.35倍,气泡能有显著增加,约为TNT炸药的1.50～2.30倍,表明在炸药中加入铝粉对于提高炸药水中爆炸威力是有益的。     

铝纤维炸药水下爆炸性能研究

将纯铝用熔喷法制成铝纤维添加到炸药中,得到新型非理想混合炸药,通过水中爆炸实验,测试不同位置铝纤维炸药的压力时程曲线。对压力时程曲线进行分析,计算得到水下不同位置铝纤维炸药的冲击波压力峰值、冲量、冲击波能和气泡能。结果表明:铝纤维炸药的压力时程曲线可采用指数函数与双曲线函数进行分段描述,而用正态分布函数拟合气泡脉动压力曲线的效果不理想;铝纤维炸药水下爆炸比气泡能与总能量的比值为52%~58%,说明向基体炸药RDX中添加铝纤维对总能量有影响;总能量与爆热的比值为75%~85%,小于理论近似值(100%),说明铝纤维炸药爆炸时铝纤维反应不完全且破碎铝纤维消耗了一定的能量。     

快速凝固高强铝合金粉的爆炸烧结

 本文介绍了高强铝合金粉的爆炸烧结试验，通过试验，现已能用爆炸法烧结成Φ20×60 mm的无中心孔且质量均匀的棒材，密度超过了理论密度的98%，金相组织分析表明：绝大部分粉末颗粒边界连接得很好，颗粒内部保持粉末材料的固有特性。     

含铝炸药水中爆炸冲击波相似律适应性探索

针对含铝炸药非理想性显著的特点,探索其水中爆炸后远场冲击波相似律的适用性。实验在8 kg当量TNT的爆炸水池中进行,在距离爆心不同位置处测量了冲击波压力剖面曲线,得到了峰值压力和压力衰减时间,结合量纲分析方法和含铝炸药的特点,对冲击波相似律适用性问题进行了探讨。实验结果表明,对于含铝炸药来说,存在着峰值压力相似而时间常数不太相似的特点,这与铝粉的二次反应放能有关。     

铝粒径及成型压强对Al/PTFE冲击反应的影响

采用模压烧结法制备了不同成型压强下铝粉粒径分别为10、30和200μm的Al/PTFE试件,基于分离式霍普金森压杆(SHPB)试验装置进行冲击引发试验,试验过程中通过高速摄影装置记录活性材料的反应情况。试验结果表明:随着成型压强增大,试件的冲击反应速度阈值均呈现先增大后减小的趋势。铝粉粒径为10和30μm时,较高成型压强的试件能够于点火延迟时间1000～1100μs处发生反应,使试件冲击反应速度阈值骤降;铝粉粒径为200μm时,活性材料点火延迟时间均在600μs附近。在相同成型压强下,试件的冲击反应速度阈值随铝粉粒径增大而升高。活性材料的冲击点火反应与材料的微观缺陷、应力波在SHPB装置中的传播、应力脉冲幅值以及材料的破坏过程等因素相关。     

沉积在液体衬底上连续铝薄膜的微观结构

研究了沉积在硅油衬底表面的连续铝薄膜的微结构及其表面形貌.与沉积在单晶硅表面的铝薄膜相比,两种铝薄膜均属颗粒结构,但硅油表面的铝薄膜具有颗粒尺寸较小、大小不均匀,表面起伏较大等特点,而且在该铝薄膜边缘的下表面,有一明显的波纹状楔型结构,其斜率仅为10^-4—10^-5.实验结果表明：这一现象是由于液体衬底的热膨胀行为引起的.此外对样品的晶态也进行了研究. 关键词： 铝薄膜 液体衬底 微观结构     

不同包套材料对MgB_2超导线材性能影响

采用原位粉末套管法(in-situ PIT)制备了不同包套材料的MgB2线材,前驱粉末按照Mg:B=1.1:2的比例将Mg粉和B粉混合均匀,分别装人低碳钢、316L不锈钢以及Monel管中,均拉拔至直径1mm,然后800℃保温10min.对烧结后的线材进行微观形貌、相成分以及超导电性的分析检测.结果表明,MgB_2/Monel线材内部粉体中生成MgNi_2相,使其临界电流密度减弱;MgB_2/SS线材由于MgB_2粒径较大,使其高场下的J_c值较差;MgB_2/Fe线材的超导电性最好,在10K,0T时J_c高达5.3×10~5 A/cm~2.     

铝粉点火微观机理的光谱研究

 铝粉是一种含能高的材料，它被广泛地添加到含能材料中。利用3台单色谱仪和OMA谱仪等多种谱仪技术，研究了铝粉在几种不同环境下的快速反应微观特性。研究表明：铝粉冲击波点火的临界条件和铝粉的物理状态相关。微米铝粉点火的临界温度为2 100 K，它接近Al₂O₃的熔化温度。它表明，在空气中容易氧化的微米铝粉点火，必须使铝粉表面的氧化层熔化。在气相反应中，微米铝粉和氧的反应是主要的；和水的反应是次要的。减小微米铝粉的颗粒尺寸，可以明显提高快速反应温度。 含铝复合燃料中的液体燃料反应后的铝粉才能参与反应；铝粉添加至气相反应介质后将明显提高反应温度。     

爆炸压实制取W-Cu纳米复合材料的实验研究

采用机械合金化法制备了W-Cu合金粉末。将制备出的W-Cu合金粉末置于爆炸压制成型的装置中进行爆炸压实,得到了最高致密度达98%的W-Cu合金。利用X射线衍射(XRD)分析了W-Cu混合粉末的合金化过程,研究了W-Cu合金粉末的还原温度对压实坯致密度的影响。通过电子探针微量分析仪(EPMA)观察了样品内部的成分与元素分布,利用扫描电子显微镜(SEM)对样品断口形貌进行了观察,并对样品的维氏硬度和电导率进行了测量。结果表明,W-Cu合金化粉末在爆炸冲击波作用下能够结合成高致密体,复合材料具有高硬度、组织均匀、晶粒细小的特点。     

Development of ultrafine-grained tungsten-based materials for applications under conditions of high-velocity impact

The effect of green porosity of powder specimens and dispersion of nanostructured tungsten powder specimens on the density of sintered alloys of the tungsten – nickel system is investigated. It is shown that the maximum density of the alloys is achieved during liquid-phase sintering of powder compacts for one hour irrespective of their initial porosity within the range from 30 to 65 vol.%. Dispersion of the nanostructured tungsten powders also affects the final porosity. Using the calculations and experimental studies, the effective penetration of cylindrical striker bars made from the WNi-91 tungsten-nickel alloy into steel plates is investigated.     

Preparation of Fe–Si–B–Nb amorphous powder cores with excellent high-frequency magnetic properties

FeSiBNb amorphous powder cores were prepared with the amorphous powder by gas atomization and subsequent hot pressing of resulting powder after creating oxide layers on the amorphous powder. Fully amorphous FeSiBNb powders with good soft magnetic properties were successfully obtained in the particle size range below 100 μm. FeSiBNb amorphous powder cores exhibit stable permeability up to 10 MHz, showing excellent high-frequency characteristics.     

电极感应熔化气雾化制粉技术中非限制式喷嘴雾化过程模拟

电极感应熔化气雾化(electrode induction melting gas atomization, EIGA)是一种制备超洁净无夹杂物的先进制粉技术,本文以粉末高温合金的氩气雾化过程为研究示例,对现有用于实际生产的国内某厂家提供的EIGA用非限制式喷嘴进行建模,采用商用计算流体力学软件FLUENT,分布采用欧拉-欧拉VOF(volume of fluid)多相流方法与欧拉-拉格朗日DPM (discrete phase model)离散相方法,对非限制式环缝喷嘴主雾化与二次雾化过程进行了数值模拟.通过对主雾化过程中多相流大涡模拟速度流场,主雾化过程中不同阶段高温熔体云图模拟以及二次雾化过程中TAB (Taylor analogy breakup)模型速度流场及TAB模型粒度分布的模拟研究,实现了对EIGA制粉技术中非限制式喷嘴雾化过程的全过程模拟,并预测了雾化后的粉末粒度分布.在此基础上,采用本文模拟使用的非限制式环缝喷嘴,设定与模拟条件一致(进气压力4 MPa,液流直径约4 mm)的实验条件,制备的粉末大部分颗粒的直径大小在100μm左右,该实验结果与模拟得到的粉末直径D50=100μm大小一致,进一步验证了模拟数据的合理性.该方法也适用于非限制式喷嘴里,其他金属或合金的雾化过的模拟研究.     

Powder compaction,sintering, and rolling of ultra high molecular weight polyethylene and its composites

The applicability of powder compaction and sintering techniques to the processing of ultra high molecular weight polyethylene (UHMWPE) powder is demonstrated. With proper processing procedure and type of UHMWPE powder, the mechanical properties obtained are nearly equivalent to those obtained by conventional melt processes. The properties were optimized by selection of a sintering temperature just above the melting point and by close control of particle size and distribution. The processability of UHMWPE is dependent on the morphology of the powder. Only those powders with a fibrous morphology provided good mechanical properties after sintering. The mechanical properties of powder compacts can be improved by several techniques. Liquid sintering with added normal molecular weight polyethylene, with close control of particle size and distribution and amount of the second component, yielded improved properties. Composites of UHMWPE, with short glass and graphite fiber reinforcement, processed by powder compaction and sintering resulted in increased modulus. The properties of these composites depended upon the amount of fibers, fiber length, fiber-matrix bonding, and fiber orientation. Rolling the powder-processed UHMWPE oriented the structure and improved the mechanical properties, although it decreased the mechanical properties of the glass and graphite fiber composites because of debonding between fiber and matrix. The properties of carbon black—UHMWPE mixtures were improved by rolling because of a more uniform distribution of carbon black.     

Rapid Consolidation by Spark Sintering of Rapidly Solidified 7075 Aluminum Alloy Powder

Compacts of 7075 aluminum have been produced from rapidly solidified powders by optimizing spark sintering parameters, such as pulse discharge time, fixed maximum temperature, holding time at this temperature, and method of cooling to room temperature after the sintering. High-grade compacts can be obtained by a short process (40-50 s) consisting of heating to 773 or 873 K at a heating rate of 9.6 K/s and holding this temperature for 10 s. The rapidly cooled compacts show the same supersaturated state at room temperature as the received as-atomized powder. Compacts quenched in water just after spark sintering at 873 K for 1.2 ks show the same age-hardening behavior as solution-heat treated compacts. Compacts that are quenched in water and aged after sintering at 873 K for 1.2 ks show the same elongation and flow stress as compacts aged after solution heat treatment. Elongation data suggest that compacts produced with longer holding time at a higher temperature and rapid cooling show a large amount of main alloying elements in solid solution and sufficient promotion of sintering.     

Reactions and stresses in polycrystalline diamond-metal and diamond-carbide compacts

Abstract

The kind of bonding phase has a significant influence on the microstructure and mechanical properties of diamond compacts. Microstructural studies of diamond with 5% wt. Ti and 5%wt. Tic (and also 30%wt. Tic) were carried out with a Transmission Electron Microscope. The TEM microstructural observations show differences between the metal and metal carbide bonding phase in diamond compacts. The mismatch of thermal expansion coefficients between diamond and the bonding metal or the compound induces significant internal stresses and may generate micro-cracks in polycrystalline diamond compacts. Twins and dislocations are the important details of microstructures in diamond crystals after HPHT sintering. They can appear as a result of residual stress relaxation. Results of measurements of residual stresses on a diamond compact surface by means of the “sin²ψ X-ray diffraction method are reported.     

Consolidation of cryomilled Al–Si using spark plasma sintering

Cryomilled eutectic aluminum–12% silicon powder was sintered using spark plasma sintering (SPS) to create bulk compacts. The cryomilling serves to break up and disperse the eutectic phase in the powder to create a well-distributed Si phase throughout the matrix and to modify the morphology of the Si phase from plate-like to spherical, whilst refining the aluminium grain size to the nanometric level. The effects of different sintering times and temperatures using SPS on the densification of the powder, the aluminium grain size evolution, the growth of the Si phase and the morphology change of the Si phase were investigated. The compacts were analysed using X-ray diffraction, scanning electron microscopy and optical microscopy. The initial stages of densification appear to be highly dependent on the yield strength of the powder. An estimate of the temperature gradient seen in the powder bed was made and calculated to be near 200?°C at the highest point. The Al and Si phase growth was investigated and it was observed that the Si coarsening rate is increased due to the increased volume of grain boundaries. As the Si coarsens, any pinning effect on the Al grains is lost, resulting in a highly unstable microstructure that coarsens rapidly.     

Fabrication of joint Bi-2223/Ag superconducting tapes with BSCCO superconducting powders by diffusion bonding

61-Filaments Bi-2223/Ag superconducting tapes have been successfully joined with BSCCO superconducting powder interlayer by diffusion bonding. The electrical properties of the diffusion bonding joints were tested by standard four probe method and the microstructures of the joints were also examined by SEM. Additionally, the phase constituents of the superconducting powders between the tapes before and after bonding process were evaluated by XRD analysis. The result shows that the diffusion bonding joints are superconductive. The microstructures of the joint display a good bonding with no cracks and discontinuities. The joining zones are mainly composed of Bi-2223 phase, Bi-2212 phase and a small amount of CuO, Ca₂PbO₄. At last, the phase transformations of the superconducting powders in the bonding process are discussed.