Explosive Welding Research Articles

Effect of heat treatment process on the microstructure of the interface of Ti/Al laminated composite

ABSTRACT In this paper, the effect of heat treatment process on the microstructure of the interface of Ti/Al laminated composite was studied. After explosive welding, the interface region of the Ti/Al laminated composite was composed of the bonding zone and the local melting zone. The bonding zone of the composite exhibited a wave morphology. The local melting zone was formed at the vortex of the wave bonding zone with some initial defects such as voids and microcracks, which was composed of different kinds of Ti-Al intermetallic compounds. The composite was heat-treated at 823 K, 848 K and 873 K. With the heat-treated time increased, the thickness of the bonding zone gradually increased. Based on the growth kinetics, the growth mechanism of the intermetallic compound in the bonding zone had been explained. The growth of the bonding zone was mainly controlled by the reaction mechanism and the diffusion mechanism in the early stage and the later stage, respectively. In addition, as the heat-treated time increased, the intermetallic compounds in the local melting zone were gradually transformed into Al3Ti, and the initial defects disappeared.

Experiment and simulation investigations on W/Cu components prepared by strong confinement thermal explosive welding

• A strong confinement thermal explosive welding was proposed for W/Cu composite. • The high-quality W/Cu joint specimen without damage and defects was obtained. • The microstructural evolution mechanism of the bonding interface was revealed. The first-wall materials and components are the most thermally loaded in-vessel components of a fusion machine, which are required to survive at high heat fluxes induced by the intense plasma bombardment. As a candidate material, the W/Cu composite was investigated from the aspects of choosing a feasible and preferable welding method for high performance and high strength. For this, a strong confinement thermal explosive welding technology was proposed to solve the key problems in producing high-quality W/Cu composite material without damage and shock-induced defects. The microstructural evolution of the welding interface was observed and analyzed in the paper. Combining with the numerical simulation, the evolution mechanism of the bonding interface and the changing rule of the grain structure of the material were studied. This comprehensive research allows to provide a new perspective for preparing high-quality W/Cu composite.

FEATURES OF FORMING THE VT1-0+AMG5 JOINT DURING EXPLOSION WELDING WITH THE INFLUENCE OF ACOUSTIC VIBRATIONS

The work is devoted to the study of the influence of the introduction of acoustic vibrations during explosion welding of the VT1-0 + AMg5 pair. A comparative study of joints obtained by the conventional method of explosion welding and explosion welding with the effect of acoustic vibrations in various welding modes has been carried out. The results of the study of the microstructure and mechanical properties allow us to speak about the positive effect of the introduction of acoustic vibrations during welding VT1-0 + AMg5, which consists in expanding the weldability area and reducing the volume of the melted metal in the joint zone. It is also shown in the work that the nature of surface preparation before welding can have a significant effect on the strength of the joint.

ABOUT SOME FEATURES OF EXPLOSIVE WELDING OF LARGE THICKNESS ALUMINUM WITH STEEL

The practical possibility of obtaining by explosive welding at one time of large plate aluminum with steel with a joint strength of more than 100 MPa is shown.

THE ASPECTS OF ALMG6 ALUMINIUM ALLOY DEFORMATION UNDER EXPLOSIVE WELDING

The paper presents the results of a study of the features of the deformation of the main plate made of AlMg6 in the process of explosion welding (with corrosion-resistant steel 08Cr18Ni10Ti). It was found that the end and edge sections of the main plate undergo severe deformation, as evidenced by the constructed maps of the distribution of residual deformations over the plate area. With an increase in the detonation velocity, an intensification of the deformation process occurs, which leads to the appearance of cracks and local spalling of plate fragments. In addition, the results of measurements of the elongation of the main plate showed that a noticeable longitudinal deformation of the plate begins approximately at a distance equal to 2/3 of the total length of the plate. The measured value of the beginning of elongation (240 ± 10 mm) with an accuracy of 95% converges with the calculated value (229 mm).

Studies on localized electrochemical activity of 304L SS-Zr-4 dissimilar joints using alternating current scanning electrochemical microscopy

Alternating current-intermittent contact-scanning electrochemical microscopy (AC-IC-SECM) technique is used for the first time for simultaneous mapping of local electrochemical activity and topography of as-polished, passivated and pickled 304L SS-Zr-4 dissimilar weld joint (explosive welded) surfaces in fresh water at open circuit potential (OCP) without redox mediator. The local surface activity showed good contrast and uniformity, even when the surfaces are in tilted condition and topographic resolution is in good agreement with contact and non-contact profilometry. The difference in current and impedance values on SS and Zr-4 surfaces were ∼100 nA and 200 kΩ, respectively. The images acquired on pickled 304L SS and Zr-4 surfaces after immersion in HNO3 + HF exhibited a relatively higher current and lower impedance compared to as-polished and passivated surfaces. XPS analysis of Zr-4 pickled surface revealed the presence of ZrOF2, ZrO2 and Zr, while pickled 304L SS showed a higher metallic to oxide ratio, indicating less protective thinner passive films, resulting in a relatively higher electrochemical activity. Though 304L SS in passivated condition revealed Cr-oxide enrichment, the higher metallic concentration on 304L SS, resulted in similar electrochemical activity as in as-polished condition. The quantitative XPS analysis corroborated the local electrochemical activity results obtained from AC-SECM technique.

Improving mechanical properties of an explosive-welded magnesium/aluminum clad plate by subsequent hot-rolling

As-explosive welded clad plates usually show poor ductility due to heavily deformed microstructures developed after explosive welding (EXW). In this study, the feasibility of improving mechanical properties of an EXWed Mg–6Al–1Zn–1Ca (AZX611)/Al–0.6Mg–0.6Si–0.1Fe (A6005C) (all in wt%) clad plate has been explored by subsequent hot-rolling. Increasing the thickness reduction per pass from 10% to 28% or decreasing the rolling temperature from 430 °C to 250 °C is shown to enhance tensile properties. The joint sheet rolled at 250 °C with a thickness reduction per pass of 28% shows a large fracture elongation of 15%, which is significantly higher than that of the as-EXWed clad plate, 1.2%. Microstructure characterization by means of scanning electron microscope, electron backscatter diffraction and transmission electron microscope reveals that the substantial improvement in ductility is intimately related to a significant reduction of the accumulated strain in AZX611 and A6005C alloy sheets and an elimination of the interface delamination formed during EXW. A certain degree of anisotropic mechanical properties is observed in all sheets regardless of rolling conditions, which can be ascribed to the mechanical anisotropy originated from the AZX611 and A6005C alloy sheets.

A Detailed Interface Characterization of the Explosively Welded Three-Layered Ti Gr 1/Alloy 400/1.4462 Steel Clads Before and After Heat Treatment

The presented research focused on the microstructural characteristics of explosively welded three-layered Ti Grade (Gr) 1/Alloy 400/1.4462 steel clads before and after heat treatment being of large practical potential. Scanning electron microscopy (SEM) analyses have shown that both interfaces formed between the plates are continuous and without defects. The in-depth examination was dedicated to the upper Ti Gr 1/Alloy 400 interface, located closer to the explosive material, therefore, subjected to more extreme welding conditions. The presence of cubic phase Ti2Ni, hexagonal phase Ni3Ti, and tetragonal phase (CuxNi1−x)2Ti were confirmed within the melted zones, which slightly widened due to annealing, being an essential step in the manufacturing of these modern materials. Transmission electron microscopy observations in the nano scale confirmed the preliminary chemical composition analyses collected with energy-dispersive X-ray spectroscopy in SEM. They additionally revealed the interface zone microstructure transformation due to the annealing. It was evidenced that initially mixed phases in the form of grains, after heat treatment formed irregular bands arranged in the following sequence: Alloy 400/Ni3Ti/(CuxNi1−x)2Ti/Ti2Ni/Ti Gr 1. A clear segregation of Cu and Ni forming two separate layers was also noticed. These diffusion phenomena may influence the strength of the final product, therefore need further studies regarding the prolonged annealing state.

Elucidating the Formation Mechanism of the Vortex at the Ta/Fe Explosively Welded Interface Using Microstructure Characterizations and Numerical Simulations

Elucidating the Formation Mechanism of the Vortex at the Ta/Fe Explosively Welded Interface Using Microstructure Characterizations and Numerical Simulations

Effect of the Shape of Rolling Passes and the Temperature on the Corrosion Protection of the Mg/Al Bimetallic Bars.

The paper presents the results of experimental tests of the rolling process of Mg/Al bimetallic bars in two systems of classic passes (horizontal oval-circle-horizontal oval-circle variant I) and modified (multi-radial horizontal oval-multi-radial vertical oval-multi-radial horizontal oval-circle-variant II). The feedstock in the form of round bimetallic bars with a diameter of 22 mm and 30% of the outer aluminum layer was made through explosive welding. The bimetallic bars consisted of an AZ31 magnesium core and a 1050A aluminum outer layer. Bars with a diameter of 17 mm were obtained as a result of rolling in four passes. The rolling process in the passes was conducted at two temperatures of 300 and 400 °C. Based on the analysis of the test results, it was found that the use of modified passes and a lower rolling temperature (300 °C) ensures a more homogenous distribution of the plating layer around the circumference of the core and results in an even grain decreasing, which improves the corrosion resistance of bimetallic bars compared to rolling bars in a classic system of passes and at a higher temperature (400 °C).

Effect of microstructure on mechanical properties of titanium-steel explosive welding interface

Explosive welding, as a well-known composite processing technology, can be used to weld two or more similar and dissimilar materials. Generally, periodic wavy interfaces are formed in the bonding zone during explosive welding process. The bonding strengths of the welding interfaces are largely influenced by the microstructure of the welding interface. In this paper, the effects of microstructure on mechanical properties of titanium-steel explosive welding interface were presented. The bonding interface with different microstructure at different locations of the titanium-steel welding interface can be characterized as three distinct zones due to different stages of detonation wave propagation including the detonation growth zone near the initiation point, steady detonation zone and reflection-affected zone near the far-end boundary. The microstructure of interfaces was investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrometer. It was found that a nearly straight interface with a small wavy interface was created in the detonation growth zone near the initiation point, and an irregularly wavy interface was formed in the reflection-affected zone near the far-end boundary. While a periodic wavy interface with various defects (e. g. microcracks, voids and intermetallic compounds etc.) was formed in the steady detonation zone. A small-size H-shaped specimen was used to evaluate the tensile properties of interfaces with the bonding interface perpendicular or parallel to the tensile loading direction. The results indicated that the amplitude and wavelength of wavy interfaces showed a tendency of increasing, plateauing and decreasing, corresponding to the detonation growth zone, steady detonation zone and reflection-affected zone, respectively. The mechanical properties of the bonding interface along the detonation direction also displayed a similar tendency. The periodic wavy interface in the steady detonation zone exhibited the highest strength. Notably, the defects, such as microcracks, void and intermetallic compounds in the vortex area had significant effects on the mechanical properties of the bonding interface.

Experimental and numerical investigation of microstructure and evolution of TiNi Alloy/Q235 steel interfaces prepared by explosive welding

This work presents a systematic study of microstructure and mechanical property of TiNi Alloy/Q235 steel explosive-welded interface. The structure evolution as well as the thermodynamic state during the welding process was simulated using Smoothed Particle Hydrodynamic (SPH) numerical method. The interface is featured by regular wave structure with a period of ∼400 μm and an amplitude of ∼120 μm, resulting from the periodic interaction process of jets and colliding plates. Furthermore, it was found that the waves do not form in the initial collision zone, but undergo an evolutionary process of straight-irregular small wave-steady wave transformation. Intermetallic compounds like Fe2Ti and Ni3Ti were found in melting zones, which are the source of the microscopic cracks. Even so, the interface exhibits good bonding strength of 291 MPa that is higher than the Q235 steel of 180 MPa. The nanoindentation results show the hardness values decrease at first and then increase to the initial value with increasing distance from the bonding interface. The melting zone exhibits an ultrahigh hardness of 11.06 GPa, which confirms the formation of brittle intermetallic in the melting zone.

A two steps Lagrangian–Eulerian numerical model for the simulation of explosive welding of three dissimilar materials joints

Explosion welding (EXW) is a solid-state joining process used to produce lap joints out of metal plates of dissimilar materials. During the process, a controlled explosive detonation results in a pressure wave pushing one of the plates to be welded, called flyer, against the other with high velocity. The high pressure and temperature generated, because of the impact energy decaying into heat, create the conditions for solid bonding phenomenon to take place. Due to the complexity of experimental tests, numerical simulation is considered a fundamental design tool for the process. Different approaches are found in literature to simulate the process. In this paper, a dual step Lagrangian–Eulerian approach is proposed to evaluate the effect of different explosives on the final quality of the weld. The numerical model was developed using the commercial software ABAQUS. A three dissimilar materials joint is considered, made of two outer plates of AA5083 aluminum alloy and A516 steel, respectively, and an intermediate layer made of AA1050 aluminum alloy. The model was first validated by comparing the wavy profile of the intermediate layer after the weld, and then used to evaluate the effect of different explosive by analyzing the distribution of the main process parameters as well as the presence of voids.

РОЗРАХУНОК НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ПЛАКУЮЧОГО ШАРУ ПРИ ПЛАКУВАННІ (ЗВАРЮВАННІ) ВИБУХОМ

Purpose. Development of a mathematical model of the process of elastoplastic deformation of the cladding layer of a layered workpiece during welding (cladding) by explosion with the formation of the objective function of optimal deformation and establishing a relationship between the parameters of welding (cladding) by explosion and the shear bond strength of the layers and the wear resistance of the cladding layer. Methodology. The solution to the problem of elastoplastic deformation is carried out using the equations of the flow theory and the nodal calculation scheme. The required deformation values are determined at the nodal mass points of the computational grid. At each moment of time, the positions of the nodes of the cladding workpiece, thrown under loading by a traveling pressure wave, are de-termined. Deformations and their intensity are determined by the position of the nodes. The task of determining the re-quired parameters of explosion welding (cladding) is reduced to the task of mathematical programming. The objective function is minimized on a family of curves, the arguments of which are the explosion welding (cladding) parameter and the welding gap. The interaction of the cladding workpiece with the pressure wave generated during the detonation of the explosive is determined by the dependences of the pressure of the detonation products, the mass velocity of the cladding workpiece and the shock wave velocity at the moment the shock wave reaches the free surface on the parame-ters of the explosion cladding (welding) with subsequent calculation of the stress-strain state of the workpieces. Accord-ing to the optimal parameters of explosion welding (cladding), a probabilistic assessment of the shear bond strength of the layers is carried out. If the strength is insufficient, the parameters are adjusted. Findings. As a result of numerical modeling, the calculation of the deformed state of the projectile is carried out. The parameters of explosion welding (cladding) are determined, at which the intensity of deformations of the cladding layer corresponds to the limit uniform ones. Based on the obtained parameters of explosion welding (cladding), the calculation of the shear strength of the layer joint was performed. Originality. For the first time, a model has been developed for the optimal deformation of the cladding layer during explosion welding (cladding) of wear-resistant compositions. The target function and the optimal process parameters have been established. A method is proposed for calculating the weighting coefficients of the objective function for multi-criteria multilevel optimization. Practical value. Recommendations for industrial application were developed and modes of explosion welding (cladding) were tested to obtain wear-resistant compositions of aluminum alloy with carbon steel.

Local structure of explosively welded titanium–stainless steel bimetal

Abstract Bimetals targeted for industrial applications are usually designed to combine the properties of two dissimilar metals, e. g. high strength, high hardness and low cost of steels with chemically resistive titanium. In this work the structure of one particular, but for industries very interesting, bimetallic system – Cr/Ni stainless steel clad with titanium has been studied. The material was prepared by explosion welding, a method capable of joining a wide variety of similar or dissimilar materials. Our analysis is based on X-ray micro-diffraction experimentation utilizing hard monochromatic X-rays focused down to micrometer size. In this way the bimetal in bulk form was analyzed and microstructural differences between the joined materials and their interface were determined.

STUDY OF WEAR RESISTANCE OF LAYERED METAL-INTERMETALLIDE COMPOSITES OF THE TI-FE SYSTEM

The paper presents the results of wear tests for the SMIC of the titanium - iron system, obtained by the technology, including explosion welding and subsequent high-temperature heat treatment, when the abrasive is exposed to the metal-intermetallic layers at an angle of 0, 45 and 90º. It is shown that more uniform wear is observed when an abrasive is applied to the layered structure of SMIC at an angle of 45º. With such a wear pattern, the best indicators of wear resistance are provided, exceeding the corresponding values for 08kp steel and VT1-0 titanium, and having a tendency to increase with increasing test temperature: +7% at 200 °C; + 13% at 400 °C and + 17% at 600 °C.

Influence of structure formation and properties of bimetal produced by ultrasound-assisted explosive welding

The aim of this paper was to study how ultrasonic vibrations during explosive welding influence the formation of the structure and properties of bimetal plate. The effect of changes in joint formation kinetics and in the structure and properties of the bimetal plate formed by explosive welding assisted by ultrasonic vibrations was determined. Ultrasound-assisted explosive welding resulted in improved strength and microhardness and decreased wave parameters and molten metal amount in the wave vortex areas compared to explosive welding without ultrasound. The influence of the propagation scheme, frequency and amplitude of the ultrasonic vibrations on the structure and property formation of the bimetal plate during explosive welding was demonstrated. The results of the influence of ultrasound on the weldable zone of dissimilar metals are discussed. Ultrasonic treatment of metal produces a decrease in yield stress, which results in modified metal surface layer properties and conditions for joint formation of collided plates during explosive welding.

Performance of fine-grained W/Cu plate prepared by explosive welding with high wave impedance confinement at room temperature

Due to the brittleness and high melting point of tungsten (W), it remains a challenge to clad tungsten layers non-destructively by an explosive welding process at low temperatures. In this study, the tungsten foil was successfully welded to a copper plate by a high wave impedance constraint explosive welding method without cracks. Electron backscatter diffraction (EBSD) and energy dispersion spectroscopy (EDS) analyses detected that the tungsten clad characterized a lamellar structure of several hundred nanometers with homogeneous elemental distribution and smooth surface. The tungsten layer maintains continuity and high hardness regardless of the cross-sectional view, and exhibits a unique wave-like bond of high strength with copper. The tensile strength of the tungsten/copper composite plate is about 391 MPa and the elongation is more than 12%. The results show that the high wave impedance constrained explosive welding method is an effective process for producing nanoscale brittle material coatings at room temperature.

Approaches to the development of wear-resistant laminatedmetal composites

Layered metal composites made of dissimilar metals and alloys occupy a special place among modern composite materials. In particular, their use is considered promising when high strength, fatigue resistance, and wear resistance are required. However, there are few data on the abrasive wear resistance of such composites, and further study is necessary. In this paper, an attempt is made to formulate some approaches to the development of wear-resistant laminated metal composites in order to promote more detailed research. For this purpose, the abrasive wear resistance at room (+25 °C) and cryogenic (−196 °C) temperatures of a layered metal composite consisting of low-alloy and maraging steels was studied. The composite was obtained by explosive welding. It is shown that the wear resistance of the composite is determined by the combined influence of a number of factors, namely the presence of interlayer boundaries, the structural state, hardness, and toughness of the steels. It is concluded that, for better wear resistance of a layered composite, the dissimilar layers must wear out evenly under existing environmental conditions.

Brass–Invar Bimetal Interface in the Joint Formed by Explosive Welding

Brass–Invar Bimetal Interface in the Joint Formed by Explosive Welding