Study On Explosive Welding Design And Interface Evolution Mechanism Based On Wave Impedance Characteristics

Explosive welding is a solid-state welding process,which is essentially a kind of:the energy conversion process of explosive explosion,the process of high-speed collision force between material surfaces,and the welding metallurgical process under high pressure,high temperature and high strain rate.In recent years,the miniaturization and functionalization of products have received widespread attention,and the research on mesoscale composite materials for the manufacture of microscopic parts and high-performance composite materials for special environments has become a trend.Compounds of new materials such as high-entropy alloys,metal composites with micro-scale structures and high-performance coatings of refractory metals,etc.At present,there are many researches on explosive welding of general industrial metal materials(such as aluminum,copper,steel,titanium,etc.),but for new process development based on mechanical properties and special performance materials(high melting point and high hardness tungsten,ultra-thin metal composite sheet,high-entropy alloys,etc.)is less.The fine grains and uniform microstructure of composite materials are very important for manufactured parts,because these factors affect reliability and strength.The bonding strength of the interface of the traditional coating process is weak,and the thermal effect during high temperature processing may damage the performance of the composite material.It is well known that due to the severe plastic deformation during the wave formation process,the wave interface in the explosive welding process is strengthened.Grain refinement can enhance the mechanical properties of the composite interface and its bonding quality.Explosion heat and shock waves generated by explosives during welding can cause ablation and shock wave damage to metal flakes,brittle materials or low-strength materials and their surfaces.These types of composite materials are difficult to manufacture with high quality in traditional welding processes.In addition,due to the inconsistent welding characteristics of different metals,the influence of the mechanical properties of the metal on the characteristic morphology and evolution mechanism of the wavy bonding interface has become a key issue.Based on the characteristics of wave impedance,this paper innovatively uses underwater explosive welding technology and explosive welding technology under the constraint of metal protection plates to conduct composite tests on refractory metal flakes and high-entropy alloys.Based on the characteristics of wave impedance,the explosive welding process and composite interface are systematically studied in theory,experiment and simulation.The main research contents and conclusions are as follows:(1)Based on the wave impedance characteristics,the explosive welding process and material properties have been improved,and a variety of high-quality ultra-thin metal composite plates,refractory metal coating materials,brittle metal composite materials and high-entropy alloy composite materials have been successfully prepared..The wave impedance of a material is mainly determined by its density and speed of sound.In order to analyze the influence of wave impedance characteristics on weldability,the explosive welding window is analyzed and discussed.The energy conversion and parameter changes in the explosive welding process are analyzed theoretically,and the wave impedance characteristics in the explosive welding process are analyzed based on the energy theory(the method of changing the wave impedance characteristics of the explosive welding process is mainly in bonding metal materials)to the relevant parameters.influences.Based on the analysis of the wave impedance characteristics and improved the explosive welding process,a high-impedance explosive welding method is proposed.That is,the wave impedance distribution and mass distribution characteristics of the explosive welding structure are controlled by bonding metal plates or using fluid media,and then optimized Explosive welding process.(2)In order to reveal the evolution mechanism of the explosive welding interface waveform and the influence mechanism of wave impedance characteristics on the waveform characteristics.The SPH method was used to numerically simulate the common explosive welding material combinations with different wave impedance ratios such as titanium/steel,copper/steel,tantalum/steel.The results show that metal jets are generated at the waveform interface under different wave impedance ratios.According to the difference between the wave impedance of the cover plate and the wave impedance of the substrate,the wave interface is identified as three typical structural types:when relatively low,the reverse vortex excited by the salient jet appears,usually with a significant melting zone or The curled morphology of the vortex zone;when it is relatively high,it presents a positive vortex excited by the re-entrant jet at a relatively high temperature,usually showing a curled morphology with a significant melting zone or vortex zone on one side;when it is relatively close At the same time,the forward vortex excited by the re-entrant jet and the reverse vortex excited by the salient jet appear,which usually appear as classic wavy morphologies with significant melting or vortex areas on both sides.By comparing the analysis results of similar wave impedance ratio materials in a large number of related literatures with the characterization data of similar wave impedance ratio materials obtained in the experiment in this paper,it is found that the structural characteristics of the waveform interface obtained by the SPH method are very similar to the waveform interface morphology observed in the experiment.SPH numerical calculations confirmed the feasibility of wave impedance characteristics for predicting the characteristics of wavy bonding interface.(3)A variety of metal composite materials were manufactured through improved explosive welding methods,and the interface of composite materials was characterized and analyzed by scanning electron microscope(SEM)and electron backscatter diffraction(EBSD),microhardness tester and nanoindenter.The results show that explosive welding technology has successfully realized the preparation of explosive composite materials of sheet materials(copper,magnesium,etc.),refractory materials(tantalum,etc.),brittle materials(tungsten,etc.)and new materials(high-entropy alloys).The characteristics of the interface waveform structure have regularities related to the wave impedance characteristics of the material.The microstructure proves that the composite material prepared by the improved process has no obvious cracks or defects.The direct combination interface and the vortex zone interface show different element distribution characteristics.The microscopic characterization confirms that the experimental results are consistent with the laws of theoretical analysis and simulation calculations.