Explosive Compaction Technology Research Articles

Synthesis of Ultrafine Fe-W-Al-Ti-Ni-C-B Powders by Mechanical Alloying

The goal of the presented research was syntheses of the ultrafine and nanopowder blends by Mechanical Alloying from Fe-W-Al-Ti-Ni-B-C compositions for further application as a precursor for fabrication bulk High-Entropy Alloy (HEA) by explosive compaction technology. The presented paper describes the preliminary investigations of mechanical alloying of Fe-W-Al-Ti-Ni-B-C powders. Laboratory vibrating sieve equipment was used for sorting the initial powders for the reduction of particle size. For the experiments were used powders of Fe-W-Al-Ti-Ni-B-C system consisting of five major metallic and two minor non-metallic B and C elements were used for mechanical alloying. The crystalline coarse Aluminum, Titanium, Carbon and Nickel, fine-grained iron and tungsten and amorphous Boron powders were used as initial components. The Fe, W, Al, Ti and Ni powders were preliminary checked by “Explorer 5000 XRF” by Skyray instrument and verified. Based on the literature review, theoretical investigation and phase diagrams for mechanical alloying were selected two compositions with the following molar ratio: Fe20W15Al15Ti20Ni20B5C5; Fe25W25Al10Ti15Ni15B5C5; The mechanical alloying was realized on the high energy ball mill with zirconium oxide jars and balls. The ball to powder mass ratio was 10:1, the rotation speed was 500rpm. The process was carried out in dry conditions. The time of mechanical alloying was 5h, 10h and 14 h. The powders were prepared for preliminary analyses and assessment of particle size. The SEM and optical microscopy results of mechanical alloying are presented in the paper.

Explosive compaction technology for loess embankment settlement control: numerical simulation and field implementation

Loess covers about one-tenth of the world’s land area. While it is often used as embankment fill, loess is not an ideal construction material due to its wet collapsible nature, as it may cause significant embankment settlement and other related problems. Although explosive compaction (EC) technology has been used for many years, the challenges in experimental testing and theoretical analysis hinder its wider application. This paper contributes to the development of a design construction scheme of EC technology for loess embankment improvement through an integrated approach that involves finite element modeling, small-scale experiments, full-scale simulation and field implementation. In this study, a reliable finite element model is developed and validated through a small-scale experiment. The model is developed based on the software ANSYS/LS-DYNA®14.5 and takes into account the coupling between different materials (including soil, explosives, air and pavement). Critical performance factors such as the volume of the explosion cavity, the density of the compacted soil and the soil pressure can be obtained directly from the model. The model is then extended to simulate full-scale embankments. A sensitivity study is conducted to establish the correlations between the design parameters and the abovementioned performance factors. The relationships served as design guidelines for the successful implementation of the EC technique in an embankment section on the Cheng-Chao highway in China. The results demonstrated the feasibility of the EC technique as a ground improvement method for loess embankments, and it illustrated the effectiveness of the numerical method as a tool in design.

The shock wave compaction of ceramic powders

Joint theoretical and experimental investigations have allowed to realize an approach with use of mathematical and physical modeling of processes of a shock wave compaction of ceramic powders. The aim of this study was to obtain a durable low-porosity compact sample. The explosive compaction technology is used in this problem because ceramic powders such as boron carbide and aluminum oxide is an extremely hard and refractory material. Therefore, its compaction by traditional methods requires special equipment and considerable expenses. In order to better understand the influence of the loading conditions and, in particular, to study the effect of detonation velocity, explosive thickness and explosion pressure on the properties of the final sample, the problem of compaction of the powder in an axisymmetric case using the conditions of the above experiments have been numerically solved. Thus, using the technology of explosive compaction, compact samples of boron carbide and aluminum oxide are obtained. On the basis of experimental and numerical studies of shock waves propagation, the optimum scheme and parameters of dynamic compaction of boron carbide and aluminum oxide are determined in order to maximize the density and the conservation of the samples after dynamic loading.

Explosive compaction of aluminum oxide modified by multiwall carbon nanotubes

This paper presents experiments and numerical research on explosive compaction of aluminum oxide powder modified by multiwall carbon nanotubes (MWCNT) and modeling of the stress state behind the shock front at shock loading. The aim of this study was to obtain a durable low-porosity compact sample. The explosive compaction technology is used in this problem because the aluminum oxide is an extremely hard and refractory material. Therefore, its compaction by traditional methods requires special equipment and considerable expenses.

The fabrication of boron carbide compacts by explosive consolidation

This paper presents experiments on explosive compaction of boron carbide powder and modeling of the stress state behind the shock front at shock loading. The aim of this study was to obtain a durable low-porosity compact sample. The explosive compaction technology is used in this problem because the boron carbide is an extremely hard and refractory material. Therefore, its compaction by traditional methods requires special equipment and considerable expenses.

Synthesis and Explosive Consolidation of Titanium, Aluminium, Boron and Carbon Containing Powders

The development of modern technologies in the field of materials science has increased the interest towards the bulk materials with improved physical, chemical and mechanical properties. Composites, fabricated in Ti-Al-B-C systems are characterized by unique physical and mechanical properties. They are attractive for aerospace, power engineering, machine and chemical applications. The technologies to fabricate ultrafine grained powder and bulk materials in Ti-Al-B-C system are described in the paper. It includes results of theoretical and experimental investigation for selection of powders composition and determination of thermodynamic conditions for bland preparation, as well as optimal technological parameters for mechanical alloying and adiabatic compaction. The crystalline coarse Ti, Al, C powders and amorphous B were used as precursors and blends with different compositions of Ti-Al, Ti-Al-C, Ti-B-C and Ti-Al-B were prepared. Preliminary determination/selection of blend compositions was made on the basis of phase diagrams. The powders were mixed according to the selected ratios of components to produce the blend. Blends were processed in “Fritsch” Planetary premium line ball mill for mechanical alloying, syntheses of new phases, amorphization and ultrafine powder production. The blends processing time was variable: 1 to 20 hours. The optimal technological regimes of nano blend preparation were determined experimentally. Ball milled nano blends were placed in metallic tube and loaded by shock waves for realization of consolidation in adiabatic regime. The structure and properties of the obtained ultrafine grained materials depending on the processing parameters are investigated and discussed. For consolidation of the mixture, explosive compaction technology is applied at room temperatures. The prepared mixtures were located in low carbon steel tube and blast energies were used for explosive consolidation compositions. The relationship of ball milling technological parameters and explosive consolidation conditions on the structure/properties of the obtained samples are described in the paper.

Research on Explosive Compaction Technology and Properties of WC/Cu Composites

This paper uses the explosive compaction method to produce Cu-matrix composites. The powders of Cu and WC were prepared by high-energy ball-milling. Experiments have been performed to compact powders of Cu and WC using cylindrical configuration. The results showed that the detonation velocity had effects on the density of the compacts. The effect has been detailedly studied. The compacted WC/Cu composites have been subjected to hot rolling. The microstructure, hardness, electrical conductivity and softening temperature of the composites have also been mentioned.

BULK NANOSTRUCTURED MATERIALS OBTAINED BY SHOCK WAVES COMPACTION OF ULTRAFINE TITANIUM AND ALUMINUM

Theoretical and experimental Investigations of shock wave consolidation processes of Ti - Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al . The normal and tangential stresses in the cylindrical steel tube (containers of Ti - Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al . Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

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.