Explosive Welding Research Articles

Multi-scale modelling of deformation heterogeneities in explosively welded layered sheets

A multi-scale numerical investigation of local heterogeneities in the strain and stress fields occurring during forming of explosively welded layered metallic sheets is the main goal of the research. Explosive welding is a complex process involving various phenomena occurring in materials during an impact at high velocities and pressures, especially at the interfaces of colliding metals. As a result, the interface of the layered metallic sheets is often highly heterogeneous at the microscale level, what directly affects the sheet behaviour under subsequent forming conditions. To investigate this issue, the mesh-free numerical model of the explosive welding process is used first to recreate the characteristic features of the interface morphology. Various detonation velocities are used to provide diversified morphological features at the interface. Obtained results are then used as input data to develop the concurrent multi-scale finite element model of material behaviour under deformation conditions. The multi-scale modelling concept with explicit representation of the interface region is used. The highly refined heterogeneous FE mesh was generated in the interface region to capture local heterogeneities occurring at the microscale. Particular attention is put on numerical investigation of an influence of interface morphology in the welding zone on the development of the stress localisation that may directly lead to fracture initiation during forming.

Microstructure-related properties of explosively welded multi-layer Ti/Al composites after rolling and annealing

The processes of rolling and annealing of explosively welded multi-layered plates significantly affect the functional properties of the composite. In current research, fifteen-layered composite plates were fabricated using a single-shot explosive welding technique. The composites were then rolled up to 72% to reduce layer thickness, followed by annealing at 625 °C for varying times up to 100 h. Microstructure evolution and chemical composition changes were investigated using scanning electron microscopy equipped with energy-dispersive spectroscopy. The mechanical properties of the composite were evaluated by tensile testing, while the strengths of individual layers near the interface were evaluated by micro-hardness measurements. After explosive welding, the wavy interfaces were always formed between the top layers of the composite and the wave parameters decreasing as the bottom layers approach. Due to the rolling process, the thickness of Ti and Al layers decreases, and the waviness of top interfaces disappeared. Simultaneously, the necking and fracture of some Ti layers were observed. During annealing, the thickness of layers with chemical composition corresponding to the Al3Ti phase increased with annealing time. A study of growth kinetic shows that growth is controlled by chemical reaction and diffusion. The results of micro-hardness tests showed that after annealing, a fourfold increase of hardness can be observed in the reaction layers in relation to the Ti, while in relation to Al, the increase of hardness is even 15 times greater.

Effects of interlayer on the interfacial microstructures and thermomechanical kinetics of explosive welded 2A14 aluminum alloy-niobium composite

The explosive welding of 2A14 aluminum alloy and niobium with and without a 1060 Al interlayer is investigated by experiments and a two-step numerical simulation. Microstructure observations revealed a continuous molten layer with plenty of micro-defects at the joint interface by direct welding, and for the welding situation with an interlayer, straight and curled joints devoid of imperfections were obtained at the upper and lower interfaces, respectively. The tensile-shear strength for the direct welded samples was 84.4 MPa, while a rise of 38.2% was achieved for the composite with an interlayer. The coupled Lagrange-Eulerian simulation showed a dramatic decline in impact velocity and an obvious increase in collision area and duration due to the insertion of the interlayer, the resulting less kinetic energy loss at the joint interfaces eliminates the formation of the intermetallic compounds. In addition, the smoothed particles hydrodynamics simulation demonstrated that the distribution of strain, temperature, and pressure is more pronounced at the lower interface, and different bonding processes were elucidated for these two interfaces. The introduction of the interlayer strengthened the weldment by adjusting the way the interface accommodates the impact-induced strain.

Effect of impact loading on structural properties of multi-layered Ta/Cu, Nb/Cu and Fe/Cu plates fabricated by single-shot explosive welding

In this work, three eleven-layered composite plates based on Cu (six layers) and one of the reactive metals such as Ta, Nb or Fe (five layers) fabricated using a single-shot explosive welding process were studied. The morphology and phase composition of the interfacial layers were thoroughly investigated using scanning (SEM) and transmission (TEM) electron microscopy. The microstructural and chemical composition analyses were then correlated with micro-hardness measurements to evaluate the mechanical properties of the interfacial layers. It was found that layers near the interfaces exhibited a complex and hierarchical microstructure on various levels. Optical microscopy characterization confirmed the high quality of the composites, without voids or layers delamination. SEM analyses showed that the solidified melt regions unveiled different morphologies but always consisted of a mixture of pure Cu and Ta, Nb or Fe elements. Quantitative nano-scale analysis using TEM revealed that nanoparticles and small dendrites dominated the reaction regions. Although no brittle intermetallics were observed near all interfaces of all composites, the microhardness of the solidified melts was 2-3 times higher than those of the sheets in the annealed state.

Post–fire properties of stainless–clad bimetallic steel produced by explosive welding process

To evaluate residual resistance performance of stainless–clad bimetallic steel (SBS) structures after a fire, it is necessary to determine post–fire performance of SBS. After heating treatment, no cracks were observed in stainless steel cladding of the SBS produced by the explosive welding process. After fire exposure, separation along metallurgical bonding interface was observed in the SBS produced through the hot rolling process. The results of tensile coupon test were used to clarify effects of exposure temperature and cooling method on stress–strain curves of the SBS. The variation trends followed by key mechanical parameters of SBS with different cooling methods and exposure temperatures were investigated. After tensile coupon test, the SBS produced through different processes exhibited different failure modes. In general, although the cladding and substrate metals were the same, different processes yielded evident differences in the stress–strain properties and failure performance of SBSs after exposure to elevated temperatures.

The joining of magnesium and aluminium alloys by inclined arrangement of explosive welding

Multi-material lightweight frames are growing rapidly in a variety of industries, specifically where weight reduction, performance improvement, and cost savings are required. Magnesium alloys (AZ31B) fulfil the requirements, but they are prone to corrosion. The joining of magnesium and aluminium alloys is being suggested as an effective approach to this issue.In this study, aluminium alloy and magnesium alloy plates were joined successfully through the inclined arrangement of the explosive welding method. The interface microstructure and mechanical properties of joined plates were examined. The microstructural studies illustrated the development of a wavy interface with the Al12Mg17 intermetallic compound. The maximum microhardness values were obtained close to the interface due to extreme plastic deformation. The shear strength and ram tensile strength of the Al 5052/AZ31B welded plate were obtained 93 MPa and 146 MPa, respectively.

Microstructure and Properties of Multilayer Niobium-Aluminum Composites Fabricated by Explosive Welding

In this study, a layered composite material consisting of alternating aluminum and niobium layers and cladded on both sides with titanium plates was obtained by explosive welding. Microstructure of the composite was thoroughly studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as by energy dispersive X-ray spectroscopy (EDX) and electron backscattered diffraction (EBSD). Microhardness measurements, tensile test, and impact strength test were carried out to evaluate the mechanical properties of the composite. Formation of mixing zones observed near all interfaces was explained by local melting and subsequent rapid solidification. Mixing zones at Nb/Al interfaces consisted of metastable amorphous and ultrafine crystalline phases, as well as NbAl3 and Nb2Al equilibrium phases. Niobium grains near the interface were significantly elongated, while aluminum grains were almost equiaxed. Crystalline grains inside the mixing zones did not have a distinct crystallographic texture. Microhardness of Al/Nb mixing zones was in the range 546–668 HV, which significantly exceeds the microhardness of initial materials. Tensile strength and impact strength of the composite were 535 MPa and 82 J/cm2, respectively. These results confirm the high bonding strength between the layers.

Interfacial evolution of titanium/steel clad plates during pulsed tungsten inert gas welding

Joining titanium alloy with steel has important applications in the shipbuilding and aerospace industries. Successful titanium/steel joints fabricated by explosive welding have been reported recently. However, explosive welding is not ideal for welded structures with complex geometry. Here, pulsed tungsten inert gas (TIG) welding is introduced to promote the application of explosively welded transition joints. In this work, pulsed TIG of commercially pure titanium to mild steel with an explosively welded titanium/steel transition joint was carried out. The results showed that at peak current (Ip) ≤ 260 A, the TiC layer hampered the generation of FeTi and Fe2Ti. However, at Ip = 300 A, the TiC layer broke up, which resulted in the thickness of FeTi and Fe2Ti increasing sharply to 0.8 μm.

A New Microstructural Approach to the Strength of an Explosion Weld.

In this paper, the local stress-strain state in an explosion weld was investigated and the local strength of the welded materials near the weld analyzed. It follows from the experimental data that the explosion weld at the microlevel looks like a wavy line. In the first approximation, this wavy line may be assumed to be periodic. We used the two-scale method to analyze the corresponding interface elasticity problem. We carried out numerical computations for three of the most referenced types of weld geometry: the symmetric wave, the asymmetric wave, and the wave with crest. We found that the wave geometry of the weld leads to increase in local stress in the weld zone. The stress concentration varied from 20% to 200% in dependence on the weld geometry and the macroscopic loading. Explosion welding is accompanied by strain hardening of the materials in the welding zone. In some cases, the strain hardening may compensate for the increasing local stress. As a result, the weld may be both stronger and weaker than the welded materials.

Microstructure and texture distribution in the bonding interface of Cu/Al composite tube fabricated by explosive welding

Microstructure and texture distribution in the bonding interface of Cu/Al composite tube fabricated by explosive welding

Investigation of interfacial structure and dynamic mechanical behavior of titanium alloy laminated composites

Explosive welding is widely used in the manufacture of dissimilar metal composite plates. In this work, TC4/TA1/Ti6321 titanium alloy laminated composites were successfully prepared by explosive welding. The interfacial characteristics of the laminated composites were studied by energy dispersive spectroscopy (EDS), electron backscattered diffraction (EBSD), transmission electron microscope (TEM), and other characterization methods. The dynamic mechanical properties of the laminated composites were investigated by using the split Hopkinson pressure bar (SHPB). The results show that the interface of laminated composites was well bonded. There was a high density of crystal defects including dislocations and twins near the interface. The composite plates showed a hard/soft/hard hardness distribution as a whole, and the microhardness increased near the interface. Due to the existence of the interface, the dynamic mechanical properties of laminated composites show different results. The dynamic compressive stress-strain curve of laminated composites showed an equilibrium type, and the strain strengthening effect was lower than that of homogeneous materials. The failure mode of laminated composites was adiabatic shear failure mode.

Fabrication and Performance Tests for ODS Cu/CLF-1 Clad Plate as Divertor Heat Sink via Explosive Welding

In order to realize the effective connection of oxide dispersion strengthened copper (ODS Cu) alloy and Chinese low-activation ferritic/martensitic steel (CLF-1) manufactured for the divertor heat sink of the future fusion reactor, explosive welding is adopted for its exceptional advantages. The ultrasonic testing (UT) result reveals a soundness ODS Cu/CLF-1 bonding interface with no detectable defects or cracks. The bonding interface presents a typical wave interface. Welding hardening occurs in the interface zone and reaches a maximum at the interface. The tensile strength of the five sample joints ranges from 360 to 366 MPa and all failed on the ODS Cu side. The cyclic helium leak testing results reveal that the ODS Cu/CLF-1 joint has favorable gas tightness and no deformation. The results demonstrate the reliable joining of explosive welded ODS Cu/CLF-1 plates can meet the application requirements involving the use of the divertor heat sinks of the future fusion reactor.

Self-Organization Processes during the Formation of Copper Based Composites by Explosive Welding

Self-Organization Processes during the Formation of Copper Based Composites by Explosive Welding

Microstructure and characterization of Ti–Al explosive welding composite plate

The interface characteristics and microstructure formation of TA2-5083 composite plate after explosive welded were studied. Optical microscope and electron microscope were used to analyze the microstructure of intermetallic compounds. Furthermore, ANSYS/AUTODYN was adopted to calculate the characteristics of interface microstructure simulated by the smooth-particle hydrodynamics (SPH) method. The results show that most molten metal in the wave front stays in the wave-waist region. There was a relative velocity difference between the vortex of molten metal and the titanium tissue, resulting in that broken titanium particles being scoured by vortexes. Ti3Al was generated in the vortex, whose antioxidant capacity wound lead to the formation of cracks. Consider soldering in a vacuum environment or adding an intermediate layer to reduce interfacial defects. The temperature of the outer vortex was higher than that of inner vortex, and the vortex has a transition layer of 5 μm, which is thinner than the transition layer of 10 μm between the fly and base plate. The jet of molten metal was mostly composed of aluminum, with the jet velocity of interface reaching 3000 m·s−1 and the interface temperature rising up to 2100 K. Compared with the molten metal in the wave-back vortex, the jet temperature at the interface was higher, resulting in a thicker transition layer at the bonding surface.

Results of the research, development and production seminar for drilling and blasting

The article provides the results of the research, development and production seminar on drilling and blasting in surface and underground mine workings and special blasting. The seminar was organized by the Ural Association of Shotfirers (Vzryvniki Urala) and held on 26 May, 2022 on the territory of the UMMC Museum Complex in the town of Verkhnyaya Pyshma, with the participation of the Institute of Mining UB RAS and the Ural Department of Rostekhnadzor. Reports on the following topics were presented: special blasting in explosive welding of metals and explosive demolition; experience with nonexplosive mixtures and devices, including pulsed gas generators, in dense urban areas; the outcome of developing and testing the procedure of studying rock mass strength properties in the course of blasthole roller drilling in open pits; forthcoming innovations in Federal Law no. 116 on Industrial Safety of hazardous production sites; relevance, features and conditions of blasting under safety shelters; mining conditions for underground mining at the Donskay Mining and Processing Plant in Kazakhstan. The theoretical part of the seminar was followed by a tour of the exhibition centers of the UMMC Museum Complex including military and automotive museums, the “Wings of Victory” aviation exhibition, the “Ceremonial Regiment” exhibition centre, and an open exposition site with railway and artillery equipment.

Microstructure and mechanical properties investigation of explosively welded titanium/copper/steel trimetallic plate

In this work, a systematic investigation of microstructure and mechanical properties of explosively welded Ti/Cu/Fe trimetallic plate is presented. Smoothed particles hydrodynamics (SPH) methods is applied to simulate the high-velocity oblique impact welding process. The simulation results reproduce the formation of the wave boundary, vortex zones, and jetting, supporting and extending the presented experimental results. Combined with the SEM, EBSD, TEM and XRD examinations, Cu4Ti intermetallics are identified in the vortices and solid-solid bonded regions at Ti/Cu interface, while ultra-fine Cu grains are formed along the entire Cu/Fe interface. During explosive welding, heat transfer between the vortex zones and severely deformed layers of the parent plates induces the formation of above microstructures. Microhardness contours depict well the characterized hardness distribution across the entire Ti/Cu/Fe joints. The nanoindentation tests reveals the individual properties of the typical phases formed, i.e., Cu4Ti ∼ 11.8 GPa, ultra-fine Cu grians∼3.9 GPa. The Ti/Cu/Fe trimetallic plates show the average tensile strength of 366 MPa, with brittle fracture observed at Ti/Cu interface region.

Static and Fatigue Full-Scale Tests on a Lightweight Ship Balcony Overhang with Al/Fe Structural Transition Joints

Combination of lightweight and sustainable marine structures represents a crucial step to accomplish weight reduction and improve structural response. A key point when considering the reliability of innovative structural solutions, which should not be neglected, is represented by large-scale experimental investigations and not only by small-scale specimen analysis. The present research activity deals with the experimental assessment of a lightweight ship balcony overhang, which incorporates an aluminium honeycomb sandwich structure and Al/Fe structural transition joints obtained by means of the explosion welding technique. The ship balcony overhang was formerly designed with the aim of proposing the replacement of ordinary marine structures with green and lightweight options. Experimental investigations of a large-scale structure were performed to validate the design procedure and to evaluate the feasibility of the proposed solution. Large-scale bending tests of the ship balcony overhang were performed considering representative configurations of severe loading conditions. The experimental analysis allowed the evaluation of the structure’s strength, stiffness and failure modes. Comparisons with analogous structures reported in the literature were performed with the aim of assessing the benefits and drawbacks of the proposed lightweight structure. Fatigue tests were also performed in order to evaluate the hardening and the hysteresis loops. The collapse modes of the structure were investigated using X-ray radiography. The structural transition joints have experienced no cracks during the static and fatigue tests. The results clearly indicated that the proposed solution can be integrated in new and existing ships, even if made of steel, as the Al/Fe structural transition joints produced by explosion welding can be used to connect the ship structure to the Al honeycomb balcony. The systematic analysis of the experimental results gave valuable data to enhance the design methodology of such structures.

Структурные особенности и технология получения легких броневых композиционных материалов с механизмом локализации хрупких трещин

Introduction. Monometallic armor traditionally used in military and special equipment armaments has a number of key disadvantages that have a significant impact on the tactical and technical characteristics of the products, namely, significant weight and thickness. At the same time, composite non-metallic armors, which have been widely used recently as an alternative, in turn, are not able to withstand multiple hits in local areas of the structure due to its complete destruction or delamination. The purpose of the work: to develop the technology of obtaining a new class of multilayer metal armor materials based on light metals and alloys by explosive welding, combining high indicators of bullet resistance and structural strength along with low specific gravity. The work presents a new scheme for reinforcing the composite using explosive welding technology, which allows localizing the development of brittle cracks along interlayer boundaries with external ballistic impact on the object. Results and discussion. Reinforced composite material based on titanium and aluminum alloys is obtained by explosive welding. Rational modes of shock-wave loading, which ensure production of composite material of required quality are determined; evaluation of strength of composite is carried out. In order to improve the tactical and technical characteristics of the composite, it was proposed to form high-solid intermetallic layers in its structure due to heat treatment. Rational modes of high-temperature annealing are defined, which ensure formation of intermetallic layers of preset thickness in composite structure. The phase composition of intermetallic pro-layers is studied. Structural features of the composite material are investigated. Mechanism of brittle cracks localization in composite structure at ballistic impact on it is described.

The role of physical properties in explosive welding of copper to stainless steel

This paper investigates the effects of the physical properties on the microstructure and weldability of explosive welding by joining two metals with a significant contrast in thermophysical properties: stainless steel and copper. Sound welds between stainless steel and copper were obtained, and the interfacial morphology was wavy, regardless of the position of the materials. The weldability of dissimilar pairs was found to be more dependent on the relationship between the physical properties of the base materials than on the absolute value of the material property. When there is a significant difference in thermal conductivity between the flyer and the base plate, together with a material with a low melting temperature, the weldability of the pair is often poor. The relative position of the plates affects the interfacial microstructure even when similar morphologies are found. For the metallic pairs studied, the wave size was bigger for the configuration in which the ratio between the density of the flyer and the density of the base plate is smaller. The same phenomenon was observed for the impedance: bigger waves were found for a smaller ratio between the impedance of the flyer and the impedance of the base plate.

Copper plating on bonding properties of aluminium/steel explosive welded composite plate

In order to reduce critical impact velocity and enlarge weldability window of aluminium/steel explosive welding, a chemical copper plating layer as interlayer was proposed to carry out aluminium/steel explosive welding. The results showed that the interface of the 1060/Q235 composite plate had good bonding performance, and no obvious defects such as cracks and pores were found. Copper plating as intermediate layer could enlarge aluminium/steel weldability window. The thickness of solidified melt was much thicker than that of diffusion zone. The molten copper particles participated in the formation of re-entry jet, which rotated under the action of initial jet. The presence of the Cu layer reduces the occurrence of excessive melting during welding and improves the properties of the interface.