Explosive Welding Research Articles

Fabrication and performance examination on explosively welded ODS-Cu / 316 L clad plate for CFETR divertor heat sink

Copper alloys are among the most promising candidate materials for divertor heat sinks owing to their remarkable advantages. However, it is challenging to use CuCrZr alloys as heat sink materials because of the harsh loading environment expected for plasma-facing components (PFCs) in future fusion reactors. Explosive welding is an effective method for manufacturing high-quality oxide dispersion strengthened copper (ODS-Cu) / 316 L stainless steel (SS) clad plates. Non-destructive testing results revealed a soundness bonding interface between ODS-Cu and 316 L without any detectable defects or cracks. In this study, optical microscopy and scanning electron microscope analysis revealed that the bonding interface did not contain any cavities and a typical wave-bonding morphology was observed. Moreover, the tensile stress of the bonding interface was higher than that of the ODS-Cu parent metal, and there was an increment in hardness on both sides near the bonding interface. The helium leak testing results indicate that the welded ODS-Cu / 316 L exhibits soundness without deformation or leakage at cyclic room and high temperatures. The results prove that the explosive welding method is a practical method for manufacturing high-quality ODS-Cu / 316 L clad plate that meet the design requirements and can provide critical references for the engineering design of the China Fusion Engineering Test Reactor (CFETR) divertor heat sink.

Phase constitution and texture distribution in the vortex zone of Co/Cu explosive welded plates

Cobalt has a reputation for its excellent electrical and magnetic properties, and exceptional wear and corrosion resistance, which has many applications in the batteries, electronic industry and semiconductor industry. In this work, the explosive welding technique was successfully performed to join Co/Cu dissimilar metals. To reveal the phase constitution and texture distribution of the vortex zone at Co/Cu joining interface, the electron backscatter diffraction (EBSD) test was carried out. It was concluded that the typical vortex structure composed of fine crystal band, sub-grains and twin structures was formed at the Co/Cu joining interface. In addition, the dynamic recrystallized structure and local internal stress at the vortex was attributed to severe plastic deformation and rapid solidification of liquid metals resulted from high strain state collision. Furthermore, the S, copper, brass and fiber deformation textures and the cube and gross recrystallization textures were confirmed at the vortex zone due to plastic deformation and dynamic recrystallization.

Post-fire performance of bonding interface in explosion-welded stainless-clad bimetallic steel

Corrosion in structural steel has significantly adverse effects on the durability of steel structures. The use of stainless-clad bimetallic steel (SCBS) produced via the explosive welding compound method was suggested to mitigate these adverse effects of corrosion. The shear resistant properties of the bonding interface had noteworthy effects on the mechanical performance of SCBS. The steel structure in service was often affected by fire, which had lasting effects on the mechanical performance of the structural steel. An experiment was conducted to clarify the effects of the exposure temperature and cooling method on the shear resistant properties of the bonding interface of the SCBS. An apparent heat affected zone (HAZ) was observed in the explosive welding area. The metallographic structure in carbon steel comprised ferrite and pearlite. The HAZ in carbon steel was mainly composed of ferrite. The changes in the microstructure of SCBS for various exposure temperatures and cooling methods were discussed. After performing mechanical tests, load–displacement curves of the SCBS specimens were obtained. Some resistance parameters were selected to clarify the effects of the exposure temperature and cooling method on the shear resistant properties of the bonding interface of the SCBS. Based on the obtained experimental results, predictive equations were suggested to reveal the variation trend of the resistance parameters. After performing a comprehensive comparison of the experimental and predictive results, it was determined that the suggested multilinear model could be used to predict the shear resistant properties of the bonding interface of SCBS effectively.

Atomic diffusion behavior near the bond interface during the explosive welding process based on molecular dynamics simulations

Based on the Hastelloy/stainless steel explosive-welded composite (the main elements are Ni and Fe respectively), this work investigated the diffusion behavior of main elements near the bond interface during the explosive welding process through molecular dynamics simulations and experiments. According to the characteristics of temperature and pressure of explosive welding process, the simulation of explosive welding process is classified into three stages, namely loading stage, unloading stage, and cooling stage. The diffusion behavior of the main elements (Ni and Fe) near the interface was investigated by two methods. The first one is to calculate the mean square displacement of the main elements. And the second one is to compare the system configurations and the results of radial distribution function at different stages. In the simulation, the thickness of the diffusion layer of the Vpx (the transverse velocity)= 0.2 km/s, Vpx= 0.4 km/s, Vpx= 0.6 km/s, Vpx= 0.8 km/s weldments are about 14, 20, 49, and 61 Å. The results show that the atomic diffusion near the interface mainly occurs in the unloading stage and the beginning of the cooling stage. Only when the melting occurs during these stages, the atoms of the bonding interface can diffuse obviously. In this experiment, the thicknesses of the diffusion layer at the wave peak and the vortex zone are about 20 µm and 230 µm respectively. This conclusion is verified by the results of experimental investigations and the references. Also, the diffusion layer thickness with the increasing the absolute value of Vpz (the longitudinal velocity) and Vpx, and the absolute value of Vpz can make a greater contribution to the thickness of the diffusion layer than that of Vpx. The thickness of the diffusion layer at the interface will be significantly increased if the melting occurred during the welding process.

Investigations on the microstructure evolution and mechanical properties of explosive welded ODS-Cu/316 L stainless steel composite

In this paper, the explosive welding technique was introduced to manufacture ODS-Cu/316 L stainless steel composite. The experimental and numerical investigations were carried out on the microstructure evolution as well as mechanical properties of the bonding interface. In both microstructure observations and mechanical tests, an excellent bonding quality of ODS-Cu/316 L stainless steel clad was confirmed, supporting that the explosive welding technology is a feasible way to fabricate high-quality ODS-Cu/316 L stainless steel joints. The EBSD results revealed a remarkable diversity of the grain structure at the bonding interface, including elongated grains, rectangular grains, equiaxed fine grains and columnar grains. The simulation reproduced the wavy interface observed in experiment accurately and forecasted the thermomechanical behavior of interface adequately, giving an opportunity to elucidate the observed phenomena.

Interfacial Microstructure and Mechanical Properties of Explosively Welded Mg/Al Alloy Plates

The interfacial microstructure and hardness of cladding plates produced by explosive welding between magnesium alloys having different aluminum concentrations and A6005C aluminum alloy were investigated. Further, measurements of residual stress at the interface of cladding plates were performed. In all cladding plates, the bonding interface had a wavy shape. Adiabatic shear bands were formed at the interface on the magnesium alloy side and deformation twins appeared at the interface due to the impact of explosive welding. Microstructure observation using scanning transmission electron microscope revealed that a thin interlayer was formed at the interface in all cladding plates. The thickness of the interlayer increased with an increase in aluminum concentration in the magnesium alloy, while the thickness was 1 μm or less. In the cross-section of the cladding plate, aluminum alloy showed a relatively higher Vickers hardness value compared with the magnesium alloy, and the hardness value increased when approaching the interface. However, nanoindentation tests revealed no increase in hardness was observed at the interface. Measurements of the residual stress using synchrotron radiation x-rays at the interface of cladding plates revealed a tendency for the occurrence of tensile residual stress on the magnesium alloy side and compressive residual stress on the aluminum alloy side. This might be due to a difference in the coefficient of thermal expansion between the magnesium and aluminum alloys.

Investigation of the microstructure of TC1/1060/6061 explosive composites based on experiments and numerical simulations

In this study, the microstructure of TC1/1060/6061 composites manufactured by explosive welding was investigated using experiments and numerical simulations. The results showed that the two interfaces of the TC1/1060/6061 composites exhibited an overall linear bonding interface without defects such as macroscopic cracks or pores. A melting layer caused by the adiabatic compression of air was observed, and the overall welding quality of the composites was good. There were no intermetallic compounds observed at the TC1/1060 interface, and the diffusion area was short, which formed a metallurgical bond. After heat treatment, the grains on the base plate and interlayer side of the composites formed a cubic recrystallized texture, while the grains on the flyer plate side developed a fine-grained structure. The microhardness of the base plate and flyer plate was higher closer to the interface due to the process hardening effect, while the microhardness of the interlayer remained stable. The formation process of these two interfaces was analyzed by numerical simulations, and jetting was observed at the 1060/6061 interface. The TC1/1060 interface in the numerical simulations showed a linear morphology, and the 1060/6061 interface showed a microwave morphology.

Microstructure, mechanical properties, and corrosion resistance of an explosively welded Mg–Al composite

In this study, an attempt was made to manufacture an AZ31–Al5005 laminated composite by explosive welding. A mixture of ammonium nitrate (90%), fuel oil (5%), and TNT (5%) was used as the explosive. The detonation velocity of the explosive material was approximately 3100 m•s −1 . The microstructure and mechanical and corrosion properties of the joint were comparatively investigated. Microstructural characterisation of the joint was conducted by optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). The mechanical properties were determined using micro-Vickers hardness, tensile, and Charpy impact tests. In addition, electrochemical tests were conducted on the AZ31–Al5005 laminated composite and the individual components to determine their corrosion resistance. The corrosion behaviours of the structures were determined in a 3.5% NaCl solution at room temperature using potentiodynamic scanning (PDS). The metallurgical structure and mechanical properties of the joints were within the acceptable limits.

The Tungsten Guard Limiter of 4.6 GHz Lower Hybrid Current Drive Under EAST Operations

The 4.6 GHz lower hybrid current drive (LHCD) waveguide is a dominative auxiliary heating and current drive facility in Experimental Advanced Superconducting Tokamak (EAST), but a large number of hot spots were observed on the previous guard limiter (GL) of graphite monoblocks plated with SiC during 2016&#x2013;2017 campaigns, which limited to the plasma density, the superconductor currents, and the heating power of LHCD in EAST operations and also led to the plasma disruptions due to the carbon impurity. Therefore, we developed a tungsten GL for 4.6 GHz LHCD facility employed in the operations. The thermal transfer issues are resolved with a numerical simulation method. The fluid circuit is designed symmetrically considering the interchangeability. The joint water box is schemed based on the physical requirements with explosive welding technology. The new GL experienced the plasma discharges in the LHCD operations under the conditions of <inline-formula> <tex-math notation="LaTeX">$I_{p} \sim$ </tex-math></inline-formula> 400&#x2013;600 kA, <inline-formula> <tex-math notation="LaTeX">$n_{e}~\sim ~2$ </tex-math></inline-formula>&#x2013;<inline-formula> <tex-math notation="LaTeX">$4\times 10^{19}\,\,\text{m}^{-3}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">$I_{t}\,\,\sim$ </tex-math></inline-formula> &#x2212;10 000/&#x2212;11 000 A in the plasma discharges. The maximum operated power of LHCD reached 3.7 MW and a short pulse discharge lasted 20 s at operated power of 2.9 MW. In consequence, the plasmas discharges were controlled well without any disruptions due to the hot spot reasons and ended smoothly. It indicates that the hot spots of LHCD GL ever considered as an inevitable event in the LHCD operations could be reduced to minimum via the new engineering design.

Investigation of interface microstructure and properties of copper/304 stainless steel fabricated by explosive welding

Explosive welding is a solid state welding process that is used for the metallurgical joining of two or more dissimilar metals. This paper presented a systematic study of microstructure and properties of copper/304 stainless steel fabricated by explosive welding. The microstructure and chemical composition were evaluated using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The properties were performed by the nanoindentation tests and bending experiments of the microcantilevers, and the microcantilevers were milled out using the Focused Ion Beam (FIB) system. The results showed that the interface between this couple metals presents a typical wavy structure. There are some vortex regions in front of the crest, which are strong intermixing of this couple metals. The diffusion layer and melting layer are two typical layers at the interface. The diffusion layers are formed by strongly collision points, while the melting layers only appear on the stainless steel side. The average nanohardnesses of diffusion layer and melting layer are between that of copper and 304 stainless steel. The nanohardness of this couple metals exhibits increasing trend from 0° to 60°, while decreasing trend from 60° to 90°. The nanohardness in Area 4 of the vortex region is highest, where is the highest temperature. The average flexural strength of micro-cantilevers shows the same change rules with the nanohardness.

Enhancing explosive weldability of thick precipitate-hardened alloys

Explosive welding of high-strength precipitate-hardened alloys in large thickness was very challenging but was increasingly desired with the continuous development of high-end equipment. An innovative strategy, which was previously proposed to achieve joining at the solid-solutioned state at first and improve the composite properties by later thermal treatment, was validated here using a Cu-Ni-Si-Cr alloy as a model material. Under the same welding condition, the composite welded at the solid-solutioned state exhibited a larger wave amplitude than that joined at the peak-aged state, an evident proof of better weldability. Further numerical analysis indicated that the enhanced weldability of the solid-solutioned alloy was closely related with its lower deformation resistance. The composite joined at the solid-solutioned state achieved a slightly lower peak hardness and yield strength than the counterpart for the thermally weakened deformation hardening effects and the more interfacial defects, while the electrical conductivity of them was comparable.

Welding Techniques for High Entropy Alloys: Processes, Properties, Characterization, and Challenges.

High entropy alloys (HEAs) are the outstanding innovations in materials science and engineering in the early 21st century. HEAs consist of multiple elements with equiatomic or near equiatomic compositions, which exhibit superior mechanical properties, such as wear resistance, fatigue resistance, and corrosion resistance. HEAs are primarily used in structural and functional applications; hence, appropriate welding processes are essential to enhancing the performances and service lives of HEA components. Herein, a comprehensive overview of current state-of-art-of welding techniques for HEAs is elucidated. More specifically, the article discusses the fusion-based welding techniques, such as gas tungsten arc welding (GTAW) and laser beam welding (LBW), and solid-state welding techniques, such as friction stir welding (FSW) and explosive welding (EB), for a broad category of HEAs. In addition, the microstructural features and mechanical properties of HEAs welded using different techniques were explained for a broad spectrum of HEAs. Finally, this review discusses potential challenges in the welding of HEAs.

TEM Observations of the Microstructural Changes in the Interfacial Zone of Explosively Welded Titanium/Steel Before and After Ex Situ and In Situ Heat Treatment.

This paper presents the comparison of the microstructure of the interface zone formed between titanium (Ti Gr. 1) and steel (P265GH+N) in various processing stages—directly after explosive welding versus the annealing state. Transmission electron microscopy technique served as an excellent tool for studies of the sharp interface in-between the waves. Directly after the welding process in this area, a thin layer of the metastable β-Ti (Fe) solid solution was observed. In the next step, two variants of annealing have been employed: ex situ and in situ in TEM, which revealed the complete information on the interface zone transformation. The results have shown that during the annealing at 600°C for 1.5 h, the diffusion of carbon towards titanium caused the formation of titanium carbides with a layered arrangement. Compared to our previous studies, the carbides found here have a hexagonal structure. Furthermore, changes in the dislocation structure were observed, indicating the occurrence of recovery processes. Possible reasons for differences observed in the microstructure of the interface formed due to ex situ and in situ annealing are also discussed. The microstructure observations are accompanied by the microhardness measurements, which showed that the annealing caused a significant reduction in the microhardness values.

Study on the Thermal Conductivity of Cu/Al Joints with Different Interfacial Microstructures

Three types of Cu/Al joints with different interfacial microstructures prepared by diffusion bonding, friction stir welding, and explosive welding were obtained, and the interfacial thermal conductivity was emphatically discussed in this paper. Two layers of intermetallic compounds with a width of 5∼12 μm were formed in the joint prepared by diffusion bonding. And a mixture of a supersaturated solid solution and few dispersed compounds with a thickness less than 1 μm was formed in the friction stir welding Cu/Al joint. The bonding interface of the Cu/Al explosive welding joint presented a wavy-like morphology with a width of 300∼350 μm. The interfacial thermal conductivity with different interfacial microstructure was calculated analytically using the acoustic mismatch model and compared with the measured value of the joints. The interfacial thermal conductivity mainly depends on the type of interfacial phase and its thickness. The calculated result showed that the interfacial thermal conductivity of friction stir welding joint was the highest (1∼8 × 107 W m−2·K−1). The experiment results suggested that the interfacial thermal conductivity showed the trend that explosive welding &lt; friction stir welding &lt; diffusion bonding.

Study on interface morphology and effect of gap gas in explosive welding

Study on interface morphology and effect of gap gas in explosive welding

Study on the Microstructure and Mechanical Properties of a Ti/Mg Alloy Clad Plate Produced by Explosive Welding

In this paper, the microstructure and properties of a Ti/Mg alloy clad plate manufactured by explosive welding were studied. The bonding interface was inspected by ultrasonic examination (US). The microstructure and the composition of the clad were characterized by OM and SEM. Properties were inspected by tensile test, shearing test, microhardness test and electrochemical corrosion. The results showed that the bonding interface of the clad plate was made up of straight areas and wavy areas. In straight areas, element diffusion occurred across the bonding interface. Additionally, in wavy areas, a melting zone occurred in the Mg alloy layer near to the bonding interface. Lots of light particles embedded on the melting zone. Tensile test results were comparable with the Ti sheet and the ultimate tensile strength of the clad plate demonstrated an 18% increase. The shearing strength of the clad plate was about 68–87 MPa. The microhardness of the clad plate was higher than that of the original sheets from the interface to 300 μm away. At over 300 μm, the microhardness of the clad plate decreased and approached the original sheets. Compared with the straight area, the hardness of the Mg alloy layer in the wavy area close to the interface increased by 12%. Corrosion results showed that the corrosion potential (Ecorr) absolute value of the clad plate increased by 24%, and the corrosion current density (icorr) value was 4 orders of magnitude lower, compared with the Mg alloy sheet. It was clear that the corrosion resistance of the clad plate was higher than that of the Mg alloy sheet. Cladding Mg alloy and Ti by explosive welding would improve the industrial applications of magnesium materials.

Interface microstructure and phase constitution of AA1060/TA2/SS30408 trimetallic composites fabricated by explosive welding

Multilayer metal composites based on dissimilar metals and alloys have great application value for many industries and key equipment because of excellent comprehensive properties. In this work, the AA1060/TA2/SS30408 trimetallic composites were successfully prepared by explosive welding technology. The 2D and 3D interface microstructure were characterized using field emission scanning electron microscope (FSEM) and computer tomography (CT). Meanwhile, to revel the phase constitution of two joining interfaces, the electron backscatter diffraction (EBSD) was carried out. It was concluded that both the Al/Ti and Ti/SS joining interfaces present typical wavy structures without obvious defects, an excellent bonding quality was confirmed. In addition, the 3D restructured interface morphologies indicated the characteristics looks like ripple and desert after the wind, which may be related to propagation direction of the impact wave. Furthermore, the phase constitution results show that the recrystallization and strong textures occurred at the two joining interfaces.

Simulation and experimental determination of temperature in the joint zone during explosive welding

This paper presents methods for the temperature calculation based on experimental data on the interface bond and in the heat-affected zone under conditions of impulse metal deformation during explosive welding. The methods are based on the formation of a thermocouple during the explosive welding of copper and constantan, with a hot junction on the boundary. An inverse computational solution is proposed to determine the temperature–time relationship at the interface from the measured potential distribution on one of the thermocouple reference junctions. The dependence of the joint (copper–constantan interface) temperature on time, defined by the maximum and residual temperatures, is determined. The temperature in the heat-affected zone spaced 0.3 mm apart from the weld is obtained. Major heat emission as well as metal melting occur in a narrow zone, significantly smaller than the zone of severe plastic deformation (wave formation zone). A mathematical model of the explosive welding temperature field is proposed, in good agreement with the experimental results.

Structural Transformations at the Interface of Explosively Welded Al and Ti: Experimental Research and Numerical Simulation

In this work, the features of plastic deformation of titanium and aluminum plates under high-speed impact conditions were studied. The structure and phase composition of the explosively welded bimetal were analyzed using both scanning and transmission electron microscopy. The deformation and heating of titanium and aluminum under high-velocity impact were simulated using the smoothed particle hydrodynamics method. The features of shockwave and deformation-thermal processes during the collision of plates were described. The phase composition of the weld and heat-affected zone have been studied. The contribution of the welded plates to the jet formation is estimated.

Microstructure evolution and mechanical property of W/Ta bimetal foil produced by a high wave impedance explosive welding technology

Microstructure evolution and mechanical property of W/Ta bimetal foil produced by a high wave impedance explosive welding technology