Explosive Consolidation Research Articles

Microstructure and energy release properties of W-Zr-Al energetic structural material fabricated by explosive consolidation

Multi-element intermetallic energetic structural materials (ESMs) as a new typical ESMs characterized by their high heat release properties and strength, which could be applied as reactive fragment, reactive shell and reactive shaped charge. Al-based ESMs had been extensively studied due to their excellent mechanical properties and high energy release characteristics. But, the low density of Al-based ESMs hindered its application. However, the need for higher density and energy release persists. In this work, the nearly fully dense W-Zr-Al ESMs with a molar ratio of 1.9:1:1 was fabricated successfully by explosive consolidation. The density reached 10.12 g/cm3 (97.5 % of the theoretical maximum density). Microstructure of the specimen was characterized by X-ray diffractometer (XRD), optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and transmission electron microscope (TEM). The heat treatment was used to further improve the performance of the specimen and the mechanical properties of quasi-static compression was investigated before and after heat treatment. The reaction activity and process of W-Zr-Al ESMs was discussed by differential scanning calorimetry (DSC). Besides, the impact-induced energy release tests were carried out to evaluate the reactive characteristics of the W-Zr-Al ESMs. The results indicated that high-density, good-strength and high energy release unreacted W-Zr-Al energetic materials were fabricated successfully by explosive consolidation.

Characterization of Ta-Ni-Al energetic structural material fabricated by explosive consolidation

Multi-element intermetallic energetic structural materials (ESMs) can be applied as reactive fragment, reactive shell and reactive shaped charge. As typical of intermetallics ESMs, Ni-Al ESMs have been heavily studied. However, the low density limits its application. This work proposed to improve the performance of Ni-Al ESMs by adding Ta. The nearly fully dense Ta-Ni-Al ESMs with a molar ratio 4:3:3 was successfully fabricated by explosive consolidation. The density was high up to 10.52 g/cm3 (98.3% theoretical maximum density). The heat treatment was used to further improve the performance of the Ta-Ni-Al ESMs. The microstructure characteristics were analyzed by scanning electron microscopy, X-ray diffraction and transmission electron microscope. The mechanical properties, reaction and impact-induced energy release have been systematically studied. Firstly, quasi-static and dynamic compression tests were conducted to analyze the mechanical properties of the sample before and after heat treatment. Secondly, the reaction characteristics in different atmospheres were discussed by differential scanning calorimetry and thermogravimetric analysis. The effect of the additive Ta was concerned. Furthermore, Impact-induced energy release tests on the Ta-Ni-Al ESMs were performed to understand the energy release properties. Based on these tests, the characterization of Ta-Ni-Al ESMs fabricated by explosive consolidation was obtained. There was no intermetallic formed in explosive consolidated samples. After the heat treatment, Ta-Ni-Al ESMs have good plasticity and strain rate effect. Meanwhile, under high impact velocity, the impact-induced energy release capability of Ta-Ni-Al ESMs was equivalent to Ni-Al ESMs.

Effects of microstructure on mechanical and energy release properties of Ni–Al energetic structural materials

Ni–Al energetic structural materials (ESMs) has been widely applied in defense field, because of its good mechanical and energy release properties. The effects of the microstructure on mechanical and energy release properties of ESMs are not well understood. In this study, by designing the particle size Ni:Al = 1 μm:25 μm and Ni:Al = 20 μm:25 μm, two kinds of samples, Ni continuous phase (Nicp) and Al continuous phase (Alcp), were prepared by explosive consolidation. The microstructure characteristics were analyzed by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscope. Quasi-static and dynamic compression tests were also conducted to analyze the mechanical properties. It showed that the Nicp ESMs had higher quasi-static compressive strength of 325 MPa and fracture strain of 21.3%, compared with the Alcp ESMs having the strength 275 MPa and the fracture strain 17.5%. Also, the dynamic compressive strength of the Nicp ESMs sample is higher than that of the Alcp ESMs sample. The reaction characteristics of the two ESMs in different atmospheres were discussed by differential scanning calorimetry. The result showed that the reaction temperature of the Nicp ESMs was lower. Impact-induced energy release tests on the two ESMs were performed to understand their energy release properties. The results showed that the microstructure had significant effects on the ignition velocity threshold and reaction efficiency. The Nicp ESMs has better reaction performance because of the high interface density.

Nano-bulk aluminum fabrication from nano powder mixed with micro powder by explosive consolidation

Explosive Consolidation Method has unique advantages with well prospects in the preparation and processing of bulk materials. In this paper, self-designed structure was employed to study the influence of the mass ratio of nano aluminum powder to aluminum powder on the mechanical properties of nano-bulk aluminum material prepared by explosive consolidation. And the mechanical properties and microstructure of prepared nano-bulk aluminums under various conditions were compared and evaluated based on FMCE method. The results show that for processing single nano-powder through explosion consolidation, hardly any Al powder can be oxidized into Al2O3, and the particle size can still remain at the nanometer order of magnitudes; with the increase from 0 to 100% of the proportion of nano-aluminum powder, the hardness and the compressive strength of nano-bulk aluminums increases, and the density decreases firstly, followed by subsequently increases; and nano-bulk materials prepared by single nano-powder have optimal performance by ranking the comprehensive scores of nano-bulk aluminum materials prepared by explosive consolidation under 6 conditions.

Preparation of bulk nano-aluminum materials from nanopowder using explosive consolidation

To optimize powder explosive consolidation technology, an improved explosive consolidation device capable of relieving pressure was designed. Bulk nano-aluminum materials achieving more than 98% of standard density were successfully fabricated by explosive consolidation. The effect of different detonation velocities on the properties of the consolidated aluminum was investigated by varying the ratio of the ammonium nitrate explosive (AN-TNT) and wood flour to adjust the detonation velocity. The results revealed that the production of “Mach holes” (defects produced by excess energy in a converging shock wave) can be reduced by decreasing the detonation velocity. At a detonation velocity of 2158 m/s, bulk aluminum with high density, high hardness, high strength, and uniform microstructure without any Mach holes and with a grain size of about 80 nm can be achieved. The hardness of explosively consolidated aluminum was four times that of aluminum prepared by general industrial technology, and its compressive strength double that of industrially prepared aluminum.

Characterization of Ta-Ni-Al Energetic Structural Material Fabricated by Explosive Consolidation

Characterization of Ta-Ni-Al Energetic Structural Material Fabricated by Explosive Consolidation

Fabrication of Cu-W Nanocomposites by Integration of Self-Propagating High-Temperature Synthesis and Hot Explosive Consolidation Technologies

Manufacturing W-Cu composite nanopowders was performed via joint reduction of CuO and WO3 oxides with various ratios (W:Cu = 2:1, 1:1, 1:3, 1:13.5) using combined Mg–C reducer. Combustion synthesis was used to synthesize homogeneous composite powders of W-Cu and hot explosive consolidation (HEC) technique was utilized to fabricate dense compacts from ultrafine structured W-Cu powders. Compact samples obtained from nanometer sized SHS powders demonstrated weak relation between the susceptibility and the applied magnetic field in comparison with the W and Cu containing micrometer grain size of metals. The density, microstructural uniformity and mechanical properties of SHS&HEC prepared samples were also evaluated. Internal friction (Q-1) and Young modulus (E) of fabricated composites studied for all samples indicated that the temperature 1000 °С is optimal for full annealing of microscopic defects of structure and internal stresses. Improved characteristics for Young modulus and internal friction were obtained for the W:Cu = 1:13.5 composite. According to microhardness measurement results, W-Cu nanopowders obtained by SHS method and compacted by HEC technology were characterized by enhanced (up to 85%) microhardness.

Progress with insulating nanocomposites based on ferrite plating of Sm2Fe17N3 micropowders

Abstract Typical exchange spring magnets are composed of two phases, a rare-earth hard magnetic material and a metallic soft magnetic material, whose magnetization value is higher than those of hard magnetic phases, such as α-Fe, Fe-B, or Fe-Co. A novel high-electrical-resistance composite magnet was fabricated by consolidating micron-sized ferromagnetic nitride Sm2Fe17N3 powder particles coated with a continuous nano-sized soft magnetic ferrite oxide layer, which suppressed intergrain conductivity but sustained the magnetic exchange interactions between grains [21] . A non-magnetic resin or ceramic insulator may suffice for the coated layer but gives rise to high electrical resistance of the magnet with large deterioration of magnetization. The soft magnetic ferrite oxide layer not only suppressed intergrain conductivity, but also only slightly reduced the magnetization of the magnet. At present, the only exchange spring magnet having a combination of a soft magnetic oxide and hard magnetic nitride is the ferrite/Sm2Fe17N3 composite magnet. Sm2Fe17N3 powder particles with a size of 2 μm were coated with an “iron ferrite” layer with a grain size of about 10 nm by ferrite plating, which is an aqueous process, following which the samples were consolidated by the explosive consolidation (EC) technique. The coercivity and rectangularity of the ferrite/Sm2Fe17N3 composite magnet decreased slightly compared to those of a Sm2Fe17N3 magnet. The fully dense ferrite/Sm2Fe17N3 magnet exhibited a resistivity of about 4000 μΩ cm, which is ten times larger than that of a fully dense Sm2Fe17N3 magnet. Thus, the soft magnetic ferrite layer in the composite magnet maintained the magnetic exchange coupling between ferromagnetic Sm2Fe17N3 grains and simultaneously suppressed intergrain electrical coupling to increase the resistivity. This decreased the eddy current loss and improved the high-frequency characteristics of the composite magnets. Therefore, ferrite/Sm2Fe17N3 composites are promising materials for magnets that are operated at high frequencies in advanced applications, such as electric vehicle magnets.

Synthesis of Bulk Amorphous Alloy from Fe-Base Powders by Explosive Consolidation

A Fe61Cr2Nb3Si12B22 amorphous alloy rod sample of 8.8 mm diameter has been successfully prepared through explosive consolidation. The structure and thermal stability of the as-synthesized sample have been analyzed through X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The results demonstrate that the sample still retains an amorphous structure, and the glass transition temperature (Tg), the crystallization onset temperature (Tx), the supercooled liquid zone (ΔTx) (Tx − Tg) and the reduced glass transition temperatures (Trg) (Tg/Tm) are 784 K, 812 K, 28 K, and 0.556, respectively. Its microstructure has been investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The average microhardness of the alumina compact is about 1069 HV.

Dynamic Consolidation and Investigation of Nanostructural W-Cu / W-Y Cylindrical Billets

The main purpose of presented work is to obtain W-Cu & W-Y cylindrical bulk nanostructured billets by explosive consolidation technology (ECT) in hot condition, with low porosity near to theoretical densities and improved physical / mechanical properties. Nanocomposites were subjected to densification into cylindrical steel tube containers using hot explosive consolidation (HEC) technology to fabricate high dense cylindrical billets.The first stage: Preliminary explosive densification of the precursor powder blend is carried out at room temperature with a loading intensity up to 10GPa to increase the initial density and to activate the particle surfaces in the blend.The second stage investigation were carried out for the same already predensified billets, but consolidation were conducted in hot conditions, after heating of samples in between 940-11000C, the intensity of loading was equal to 10GPa.Consolidated different type of W-Cu composition containing 10-40% of nanoscale W, during investigation showed that the combination of high temperatures (above 940°C) and two-stage shock wave compression was beneficial to the consolidation of the incompatible pair W-Cu composites, resulting in high densities, good integrity and good electronic properties. The structure and property of the samples obtained, depended on the sizes of tungsten particles. It was established that in comparison with W-Cu composites with coarse tungsten the application of nanoscale W precursors and depending of content of W gives different result.Tungsten is a prime material candidate for the first wall of a future fusion reactor. In this study, the microstructure and microhardness of tungsten-yttrium (W-Y) composites were investigated as a function of Y doping content (0.5÷2 wt. %). It was found that the crystallite sizes and the powder particle sizes were increased as a result of the increase of Y content. Nearly fully dense materials were obtained for W-Y alloys when the Y content was higher than 0.5 wt. %. Investigation revealed that the Y rich phases were complex (W-Y) oxides formed during the sintering process. Also very interesting to use doping chromium with yttrium-containing alloys. e.g. (W - 10÷12 Cr -0.5÷2 Y) wt. %. The extent up to which yttrium acts as an active element improving the adherence and stability of the protective Cr 2 O 3 layer formed during oxidation is assessed.The structure and characteristics of the obtained samples depends on the phase content, distribution of phases and processing parameters during explosive synthesis and consolidation. Cu – (10-30%) W powder mixtures were formed into cylindrical rods using a hot shock wave consolidation (HSWC) process. Different type of Cu - W precursor composition containing 10, 20 and 30% of nanoscale W were consolidated near theoretical density under 900°C; The loading intensity was under 10 GPa. The investigation showed that the combination of high temperatures (above 800°C) and two stage shock wave compression was beneficial to the consolidation of the W-Cu & W-Y composites, resulting in high densities, good integrity and good electronic properties.

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.

Fabrication of functionally graded W(Mo)–Cu composites by explosive consolidation

We considered self-propagation exothermic reaction and water-borne shock wave methods, established explosive consolidation devices and conducted explosion consolidation tests on W(Mo)–Cu materials. Tests found that the main explosive consolidation mechanism of Cu particles concluded micro-explosion and friction welding. While the mechanism of W(Mo) could be attributed to the cavity collapse and breakage, the hardness of the sample depended on the content ratios of W(Mo). The surface hardness of the sample is closed to the theoretical hardness of copper when the Cu content reached 40%. W particles were easy to be oxidised and carbonised. The results proved that it was feasible to achieve excellent quality of W(Mo)–Cu FGM with explosive consolidation method.

HOT EXPLOSIVE CONSOLIDATION OF NANOSTRUCTURED TUNGSTEN–SILVER PRECURSORS

Different precursors of refractory nanostructural tungsten-silver (W-Ag) composites were consolidated into cylindrical billets by hot explosive consolidation (HEC) method. Different types of compositions with a nanoscale W phase (100 nm) and coarse matrix phase of Ag were consolidated to near theoretical density under and above of melting point of silver (940 – 1050 °C). The intensity of loading in all experiments was around 10 GPa. The combination of high temperatures and two stage explosive densification processes was found to be beneficial to the consolidation of the nanostructural W based composites, resulting in high densities, good integrity, and good electronic properties. The structure and property of the samples depends on the value of consolidation temperature and dimension of consolidated particle. It was observed that for the W-Ag based composites, application of high temperature and consolidation of precursors near melting point of silver 940 °C gives samples without cracking with high value of density and uniform distribution of two phases. The features of structure/property relationship depending on phase content and consolidation conditions have been discussed.

Explosive Fabrication of Cu-C and Cu-W Materials

The possibility of fabrication of antifriction composites based on copper-graphite precursors using hot explosive consolidation technology is studied in the presented paper. The application of explosive consolidation technology provides high dense billets approaching the theoretical density without cracks and porous structure. The structure of fabricated billets was investigated depending on the parameters of the detonation front. As the investigation showed, the preliminary density of precursors is one of the important parameters in the offered technology. In case of low density under the shock wave front, geometry of the container changes and obtaining high dense billets becomes impossible. The pores, cracks and cavities were observed in an entire volume of these samples too.The Cu–(10-30%) W powder mixtures were formed into cylindrical rods using a hot shock wave consolidation (HSWC) process. Different types of Cu - W precursor composition were consolidated near the theoretical density under 900°C; the loading intensity was under 10 GPA.The investigation showed that the combination of high temperatures (above 800°C) and two-stage shock wave compression was beneficial to the consolidation of the Cu -W composites, resulting in high densities, good integrity and good electronic properties. The structure and property of the samples obtained depended on the sizes of tungsten particles. It was established that Cu-W composites with coarse tungsten in comparison to nanoscale W precursors give different result depending on the content of W.

Explosive consolidation of 316L stainless steel powder – Effect of phase composition

Two stainless steel (SS) AISI 316L powders have been processed by explosive consolidation using a cylindrical configuration. Powders with d50 of 9 and 5μm and a phasic structure consisting of fcc and bcc are used. After shock processing (3.5 up to 4.9mm/μs) hardness was evaluated. Powders with the lowest particle size and processed with the highest detonation velocities (4.9 and 4.1mm/μs) gave rise to a bulk material where in the centre occurred a phase transformation of bcc to fcc phase. Nevertheless, the hardness values were dissimilar along the cross section depending on the macrodefects (centre hole and cracks) produced by detonation. After a pre-heating treatment (900°C), this powder was full austenitic (fcc) and when submitted to explosive consolidation, it led a monolithic solid without cracks, with a density of 99% TMD (theoretical maximum density) and a hardness of 3.1GPa. This value is lower than others measured, particularly when a centre hole is not present, revealing hardening by plastic deformation. Concerning powder with higher particle size (d50=9μm), the presence of mainly austenite induces after shock processing function of detonation parameters and localisation hardness values from 3.9 up to 5.0GPa. The homogeneity of hardness reflex of absence of defects and low stress are almost achieved only for low particle size powders, using the lowest detonation velocities (3.4GPa).

Review on the explosive consolidation methods to fabricate tungsten based PFMs

Tungsten is one of the best candidates for plasma-facing materials in the fusion reactors, owing to its many unique properties. In the development of tungsten-based Plasma Facing Materials/Components (PFMs/PFCs), materials scientists have explored many different, innovative preparation and processing routes to meet the requirement of International Thermonuclear Experimental Reactor (ITER). Some explosive consolidation technology intrinsic characteristics, which make it suitable for powder metallurgy (powders consolidation) and PFMs production, are the high pressure processing, highly short heating time and can be considered as a highly competitive green technology. In this work, an overview of explosive consolidation techniques applied to fabricate tungsten-based PFMs is presented. Emphasis is given to describe the main characteristics and potentialities of the explosive sintering, explosive consolidation techniques. The aspects presented and discussed in this paper indicate the explosive consolidation processes as a promising and competitive technology for tungsten-based PFMs processing.

Celebrating ASM's First 100 Years in Supporting Materials Innovation: 1984-1993

Abstract In recognition of ASM International's 100-year anniversary, AM&P highlights historic events and technological advancements that occurred over the course of those years. This issue extends the timeline from 1984 to 1993, which includes the release of an artist's conception of the National Aero-Space Plane (NASP), the development of a superconducting composite produced by explosive consolidation, and the completion of the stainless-steel-clad Canary Wharf Tower in London.

Development and Performance of New Gadolinium and Boron Containing Radiation-Absorbing Composite Systems

The theoretical design and the experimental design and development of multifunctional radiation-absorbing composite material systems based on gadolinium, boron, and tungsten has been carried out. Based on theoretical calculations, the effective compositions of these composite subsystems were established for the enhanced absorption of neutron and γ irradiation in various energy spectra. In addition, the systems and systems compositions were designed and processed for enhanced multifunctional performance. Selected and optimized compositions of Gd-B-W system were densified by shock wave consolidation technology. The technological parameters for the explosive consolidation processes and the structure-properties relationships are presented and discussed. The radiation-absorbing properties of the bulk samples were investigated and measured under neutron and gamma irradiation. The theoretical design and the optimization of these composite systems were carried out by the Monte Carlo method with a GEANT 3 program, which contained a special GCALOR package for the simulation of the interaction of thermal and fast neutrons with the composite material systems. During the neutron passage through the samples, the main processes of the interaction of neutrons with matter were considered including elastic and inelastic scattering, neutron fission of nuclei, and radiation capture. The attenuation factor of the irradiation flux is determined as a criterion of efficiency of radiation absorption. For the energy of 0.025 eV (thermal neutrons), gadolinium-containing composites have the maximum absorption capability. In the range of energy spectrum from 1 eV to 10 eV, the boron-containing composites have better absorption performance. For the capture of neutrons in wide energy spectrum, the (n, γ) reaction takes place and tungsten provides enhanced absorption of radiation. In the presence of mixed radiation sources (neutron and γ quanta), the boron- and gadolinium-containing composite materials prepared on the tungsten basis have the best performance. In addition to enhanced radiation absorption properties, these composite systems show also enhancement on other properties such as corrosion resistance in aggressive media.

Quasi-static and dynamic response of explosively consolidated metal–aluminum powder mixtures

Nearly fully dense (>96% theoretical maximum density) powder mixture compacts with combinations of Nb, Ni, Mo, W, and Ta, with Al, were produced by explosive consolidation. The quasi-static and dynamic behavior and failure mechanisms were investigated experimentally and computationally. For two mixtures (Ni+Al, W+Al) the Al phase was continuous, while for the other three mixtures (Nb+Al, Ta+Al, Mo+Al), the Al phase was discontinuous. It was found that the continuous phase significantly influenced the mechanical response (in compression) and determined the fracture morphology of the compacts. Accordingly, the mixtures with continuous Al phases had the lowest compressive strength. Two distinct failure mechanisms, axial splitting and shear failure, were observed. Axial splitting occurred when the Al phase was continuous (Ni+Al, W+Al); shear failure was primarily associated with extensive deformation of the Nb, Ta and Mo continuous phases. Finite element simulations provide valuable help in interpreting the experimental results and predicting mechanical strength and failure mechanisms akin to those observed. The interfacial bonding strength is shown to be an important parameter in determining the mechanical response of the compacts.