Ti/Al_2O_3 Functionally Gradient Material Prepared by the Explosive Compaction/SHS Process

Ti1Al2O3 Functionally Gradient Material (FGM) was prepared by an explosive compaction/SHS process. Ten sheets of the compounding powder were laminated and pressed to get a green body of FGM. It was then compacted explosively By burying the explosive compaction body into a stoichiometric Al/TiO2 mixture and igniting the combustion of the stoichiometric Al/TiO2 mixture, the SHS reaction of the explosive compaction body was initiated by the heat released from the combustion of the stoichiometric Al/TiO2 mixture. In this way, Ti/Al2O3 FGM was synthesized. The adiabatic temperatures of each gradient layer were calculated when the preheating temperatures were 298 K and 1173 K, respectively The microstructure, composition and properties of Ti/Al2O3 FGM and the reaction mechanism of each gradient layer were studied. It was found that Ti/Al2O3 FGM prepared by the explosive compaction/SHS process had a high density and a high microhardness. Its structure, composition and properties showed apparent gradient distribution. The structure of the standard stoichiometric ratio gradient layer of FGM was a network structure. Its reaction mode could be described as follows: Al powder melted first, then the molten Al penetrated into the TiO2 zone and reacted with TiO2, and big pores were left in the original positions of Al powder. The reaction of gradient layers with the addition of Al3O3 as diluents was similar to that of the standard stoichiometric ratio gradient layer, so were their structure and composition. However, the reaction of gradient layers with the addition of Ti as diluents was more complex and the composition deviated slightly from the designed one

Structure and flaws of CuCr alloys by explosive compaction

CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractured surface displays ductile characteristics. In the metallurgical structure, CuCr alloys are composed of two phases of uniform distribution; the SEM morphology is like thin strips with an end arrangement that is bonded to each other and the two-phase distribution of CuCr alloys is more homogenous. It is in only in a very small zone that formation of Cu-rich and Cr-rich phases take place. The flaws of the compaction samples are mainly central-holes and cracks.

CuCr bulk alloy produced by mechanical alloying and explosive compaction

CuCr bulk alloy was produced by mechanical alloying and explosive compaction technology. Four kinds of milling time were used to analyze the function and influence on mechanical alloying. The samples were characterized by X-ray diffraction and optical microscope, and the density and hardness of the four samples were detected. The results show that the CuCr grain size is decreased with the milling time increasing, and nano-crystalline is observed in both Cu and Cr phase after 20 h milling. The density and hardness of samples are also increased with the increase of the milling time, so that the sample relative density reaches 96.6% and hardness reaches HV 217. The results indicate that high quality of CuCr bulk alloy can be manufactured using explosive compaction method when mechanical alloying and explosive compaction process parameters are reasonably selected.

APPLICATION OF HOT-PRESS SINTERING TECHNIQUE TO EXPLOSIVE CHARGE LINER OF PETROLEUM PERFORATION BULLET

A new method for manufacturing explosive charge liner of petroleum perforation bullet, using hot press sintering technique, has been introduced in the paper. The sintering process of making explosive charge liner has been investigated. The mechanical test and SEM analysis indicate that the property of the liner produced by the process is satisfied.

Safety control for powder compaction of initiating explosive device

Powder compaction is one of the most crucial processes in initiating explosive device manufacturing. The quality of powder compaction may influence the performances of product directly. Traditional powder compaction mainly makes use of manual gravitational spiral loading machine or lever loading machine. Potential accident by the strike in powder compaction of initiating explosive device could risk life, property and the environment. To prevent this risk, automatic control system and control strategy can be used to guarantee no strike in pressing process. The scope of this paper is to analyze and review the control strategy for powder compact and discuss the experimental results for the application of the proposed strategy.

Explosive compaction of CuCr alloys

The production of CuCr alloys utilizing explosive compaction was studied. Mixture powders of CuCr alloys placed in tubes with a dimension of d14.0 mm×21.4 mm can be compacted using explosive pads of 16.5 mm or 22.5 mm. Thicker pads of explosive make the compacts more porous. The effects of the ratio of m e/m p, ratio of m e/(m p+m t) and impact energy on the density of compacts were similar, they were chosen to control explosive compaction, respectively. When adequate value of the parameters m e/m p, m e/(m t+m p) and impact energy of unit area of tube was chosen, high density(7.858 g/cm 3), high hardness(HB189) and low conductance (13.6 MS/m) of CuCr alloys could be made by explosive compaction. The general properties of CuCr alloys by explosive compaction are similar to those of CuCr alloys by traditional process.

EFFECT OF EXPLOSIVE CONSOLIDATION PARAMETERS ON CONSOLIDATION QUALITY

Two-dimension consolidation under the cylindrical converging shock wave has been studied. The major parameters influenced on the explosive consolidation quality are the specific energy,detonation pressure and specific impulse.It seems to be favourable to improving con- solidation quality by a lower but slightly higher than critical detonation pressure and a high specific impulse.

EFFECT OF EXPLOSIVE CONSOLIDATION PARAMETERS ON CONSOLIDATION QUALITY

Two-dimension consolidation under the cylindrical converging shock wave has been studied. The major parameters influenced on the explosive consolidation quality are the specific energy,detonation pressure and specific impulse.It seems to be favourable to improving con- solidation quality by a lower but slightly higher than critical detonation pressure and a high specific impulse.

EXPLOSIVE CONSOLIDATION OF METALLIC FILAMENTS UNDER CYLINDRICAL CONVERGING SHOCK WAVE

Two dimensional explosive consolidation under cylindrical converging shock wave has been studied by use of coated fine iron filaments compacts to replace conventional metallic powder, so the randomness of three-dimensional spatial distribution of metallic powder might be avoided.The deformation and surface flow pattern of particles as well as the mechanism of consolidation have been clarified experimentally.The distribution of high temperature area is in agreement with the result of numerical simulation by Williamson.A model for the explosive consolidation was given.

EFFECT OF OXIDE LAYER THICKNESS OVER Al AND Al ALLOY POWDERS ON QUALITY OF THEIR EXPLOSIVE COMPACTS

Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults indicate that super quality explosive compact can only be obtained by powders of which the thickness of the oxide layer is less than 30 nm.

Microstructure of explosively compacted Nd-Fe-B magnet by TEM

The microstructure of an explosively compacted Nd-Fe-B permanent magnet（Nd-Fe-B） was investigated by means of TEM and XRD. It is shown that there are three kinds of phases: Nd2Fe14B matrix phase, O-rich phases and Nd-rich phase with different structures and compositions in the magnet. The hard magnetic phase Nd2Fe14B is tetragonal, which lattice parameters are determined to be a=0.88 nm and c=1.22 nm. The O-rich phase locates at the grain boundaries and the triple junctions has fcc structure whose lattice parameter is a=0.559 nm. A dislocation is observed in this phase. It is also found that a large number of the block-shaped Nd-rich phases with hcp structure are embedded in the Nd2Fe14B matrix or at grain boundary. Their lattice parameters are determined to be a=0.395 nm and c=0.628 nm.

Compaction of TiAlMn Alloy Powder by Explosion and Sintering

Direct explosive compaction and sintering of a mixture of Ti-30Al-2Mn(wt%)and Ti-38Al-2Mn(wt%) intermetallic compound powders were carried out.Microstructure and phase characteristics of the alloys were analysed by TEM,SEM,X-ray diffractometry and optical microscopy.The results showed that the rel- ative density of the samples which were explosive-compacted and sintered reached 99.90%,and fine grain structure was obtained.Through the explosive-compacting and then sintering at 1373 K in argon atmos- phere,mutual diffusion between Ti-30Al-2Mn particles and Ti-38Al-2Mn particles took place and TiAl phase was formed in the alloy.TiAl based alloys prepared by high-energy ball-milling powders had much fi- ner grain size than those prepared by general ball-milling powdeis.

TiB_(2)/B_(4)C复相陶瓷自蔓延热爆炸烧结与性能表征

为了探究高硬度复相陶瓷高效且低成本的制备方法,利用自蔓延高温合成结合爆炸烧结技术,开展制备二硼化钛/碳化硼(TiB_(2)/B_(4)C)复相陶瓷的研究,成功制备厚度约为1 cm、直径约为5 cm的TiB_(2)/B_(4)C复相陶瓷块体。烧结样品物相和微观结构分析表征结果表明:烧结样品中TiB_(2)相和B_(4)C相分布均匀,截面观察到致密的微米级颗粒。该方法制备的样品致密度和硬度较高,随冲击压力不同,致密度范围在90%~93%之间,相应平均维氏硬度为16.64~17.35 GPa;根据不同条件下回收样品的微结构、致密度等分析,冲击压力和起爆时刻生坯温度对TiB_(2)/B_(4)C复相陶瓷烧结质量有重要影响;冲击压力为40 GPa,生坯温度为1800 K时,烧结致密度为93%;为进一步提高烧结质量,应提高冲击压力或冲击波作用时间。研究表明自蔓延热爆炸烧结技术是一种高效且低成本的高硬度复相陶瓷的制备方法。

装药结构对爆炸压实W-Cu粉末的影响

在爆炸压实技术中,粉体中激波和稀疏波的强度及作用时间直接影响压实体的质量。为探究爆炸压实中不同因素对粉体中压力变化的影响,基于AUTODYN有限元程序,建立了爆炸压实W-Cu粉末的有限元模型,通过流固耦合算法实现炸药、盛粉管和W-Cu粉末的相互作用。建立与现有试验对应的有限元模型,模拟结果和试验结果具有较好的吻合性,验证了模型和材料参数的可靠性。通过对爆炸压实过程的数值模拟,分析了装药厚度和盛粉管厚度对爆炸压实压力的影响。结果表明,装药厚度越厚,激波压力的作用时间越长,对粉末的压实越有利;随着装药厚度的增加,作用时间的增长减缓。盛粉管厚度越厚,粉体中稀疏波的强度越低,对压实体的影响越小;但随着管厚增加,粉体中心压力将会降低,粉末的压实质量下降;故选择盛粉管厚度时,需综合考量粉体中心压力和稀疏波强度对爆炸压实体的影响。

深厚软基超长防波堤爆炸挤淤快速施工技术

含有深水较厚淤泥层的软基加固处理难度大,海上施工工况复杂,一直是软基处理工程的难点。在渔港斜坡式防波堤建设工程中,针对淤泥层厚、抛填方量大、防波堤长度大的特点,采用爆炸置换方法进行挤淤施工。防波堤总长2 180 m,抛石量约434万m3,为加快施工速度,构筑了双人工岛施工方法,人工岛尺寸为36 m×36 m,增加了同时工作面。在合拢段采用子堤拓宽法施工,子堤宽度8 m,由内侧向外侧推进完成合拢。经沉降点观测和钻孔取样,防波堤建设取得了较好的质量效果,可为相似工程提供借鉴经验。

CONSOLIDATION BEHAVIOR OF MECHANICALLY ALLOYED γ-TiAl

Use of mechanically alloying for preparation of Ti-35at.%Al results in significant reduction in crystal size, so the ductility of alloy can be improved Consolidation of Mechanically alloyed γ -TiAl is difficult because of its poor workability. The present paper will discuss recent studies on consolidation behavior by using different methods, such as explosive compaction, hot isostatic pressing, and rapid omnidirectional compaction, etc.. The microstructure and property of the samples are evaluated.

Coating processes towards selective laser sintering of energetic material composites

This research aims to contribute to the safe methodology for additive manufacturing(AM)of energetic materials.Coating formulation processes were investigated and evaluated to find a suitable method that may enable selective laser sintering(SLS)as the safe method for fabrication of high explosive(HE)compositions.For safety and co nvenie nce reasons,the co ncept demonstration was conducted using inert explosive simulants with properties quasi-similar to the real HE.Coating processes for simulant RDXbased microparticles by means of PCL and 3,4,5-trimethoxybenzaldehyde(as TNT simulant)are reported.These processes were evaluated for uniformity of coating the HE inert simulant particles with binder materials to facilitate the SLS as the adequate binding and fabrication method.Suspension system and single emulsion methods gave required particle near spherical morphology,size and uniform coating.The suspension process appears to be suitable for the SLS of HE mocks and potential formulation methods for active HE composites.The density is estimated to be comparable with the current HE compositions and plastic bonded explosives(PBXs)such as C4 and PE4,produced from traditional methods.The formulation method developed and understanding of the science behind the processes paves the way toward safe SLS of the active HE compositions and may open avenues for further research and development of munitions of the future.

镁铝复合板制备及成形技术研究进展

镁铝复合板是在镁合金外表上面覆盖一层铝而形成的铝–镁–铝三明治复合板,与镁合金相比,复合板的耐蚀性能得到有效改善,成形能力得到显著提高。对镁铝复合板制备方法及成形工艺进行了综述,介绍了镁铝复合板不同制备方法的研究进展,并对比分析了不同制备方法的优缺点,分析了现有镁铝复合板结构成形方法的不足之处,并提出了相应的解决途径,为镁铝复合板结构在航空航天领域的应用提供参考。

黏土中爆炸成坑地冲击耦合效应实验研究

为获得黏土中爆炸成坑体积与耦合地冲击能量的关系,采用10.5 g TNT厘米级球形炸药球作为爆炸源,在Φ1500 mm×1490 mm分层式爆炸装置中开展了变埋深条件下的爆炸实验,利用3D扫描设备记录不同埋深下弹坑的真实体积,并通过动态土压力传感器测得地冲击传播衰减规律。实验结果表明:随埋深增大,耦合至黏土中的有效地冲击能量急剧增大,装药中心下方的有效弹坑体积与耦合至黏土中的有效地冲击能量基本呈正比关系,当装药比例埋深与封闭爆炸条件下爆炸空腔半径相当时,耦合至黏土中的有效地冲击能量基本达到饱和。结合实验结果给出了黏土中爆炸耦合地冲击能量分配随装药比例埋深的变化规律,建立了地下爆炸等效封闭当量计算方法,为地下工程抗爆设计提供了理论依据。

不同初装粉末条件对爆炸压实铜锡合金的影响

为避免传统粉末冶炼工艺易使铜锡合金产生缺陷而影响其强度,用爆炸手段对铜锡粉末进行压实,研究不同初装密度、不同粉末颗粒下铜锡粉末的压实效果。结果表明:铜锡粉末颗粒度从10μm减到1μm时,铜锡合金的密度增加,压实效果更好,当颗粒度减到200 nm时,因颗粒度减小,比表面积增加,导致粉末压实能量增大,影响压实效果,压实后的铜锡合金密度略小。但整体来看,试件硬度随颗粒度的减小而增大;当初装密度从43%增至52%时,基本无缺陷,铜锡合金棒材的密度提升,整体硬度增加,压实效果更好,但当初装密度超过52%后,初装密度的增大对压实效果影响较小。