Study On Interface Characteristics And Evolution Mechanism Of Explosive Welding For Metal Tube And Stick

During the 14 th Five Year Plan period,the Ministry of Science and Technology of the People’s Republic of China deployed research and development tasks for advanced structures and composite materials to meet the needs of powerful countries such as industrial manufacturing,transportation,and aerospace construction,with a focus on forming a systematic independent research and development and support capability for domestic materials,and achieving domestic independent supply of key structures and composite materials urgently needed in fields such as space applications,rail transit,energy equipment,and deep sea and deep ground.For the preparation of advanced structures and composites,the current mainstream manufacturing process adopts mechanical and metallurgical combination to achieve high strength interface bonding for metal combinations with poor plastic deformation ability,large melting point difference and low hot working performance.Compared to mainstream manufacturing processes,explosive processing technology can achieve a wider range of metal combinations.By generating high-speed detonation waves and huge energy detonation products through explosive explosions,metal materials collide,causing plastic flow and element diffusion at the bonding interface at high temperatures and pressures.Ultimately,composite materials with excellent bonding interface can be generated.At present,the research progress of explosive welded metal tube and stick structure is relatively less due to its difficult charging,serious external constraint die loss and easy over-welding damage,etc.At the same time,the research on the microstructure,interface strengthening characteristics and interface evolution mechanism of the welded metal tube and stick interface is still insufficient.Therefore,taking SS304 tube and stick,Cu/Al and Ni/TC18 composite tube as the research object,this thesis carried out systematic research on the optimization of explosive welding process parameters,theoretical verification of welding window,analysis of welding interface characteristics and numerical calculation of interface evolution,and conducted in-depth research on the bonding characteristics and macro and micro evolution mechanism of explosive welding interface.The main research contents are as follows:(1)The relationship between the process parameters of explosive welding was studied by deducing the explosive composite Gunny model and the weldability window of explosive welding,and the processing parameters of SS304 tube/stick,Cu/Al and Ni/TC18 composite tube were determined for the explosive welding test.(2)Through explosive welding of SS304 tube/stick and Cu/Al composite tube,the radial direction-tangential direction section(RD-TD)and radial direction-axial direction section(RD-AD)after welding were characterized by optical microscope(OM)and scanning electron microscope(SEM)to analyze the waveform structure of the bonding interface in different sections;Characterization and analysis of interface element diffusion behavior and micro plastic deformation modes based on elemental scanning(EDS)and electrical scattering back diffraction analysis(EBSD);Quantitative analysis using a microhardness tester combined with the distribution pattern of interface hardness strengthening.(3)Through explosive welding of Ni/TC18 composite tube,the wave structure of bonding interface in different sections was observed by SEM;EDS and EBSD were used to characterize and analyze the diffusion laws of interface elements and micro plastic deformation modes;Characterization and analysis of the layered phase structure and grain micro plastic deformation mode within the transition interface were carried out using telescope electron microscopy(TEM)and high-angle annular dark field scanning transmission electron microscopy(HAADF-STEM);Quantitative analysis using a microhardness tester combined with the distribution pattern of interface hardness strengthening.(4)Based on the ALE method,the explosive welding model of SS304 tube and stick was established by fitting the JWL constitutive model of explosives;Based on the SPH method,a simplified two-dimensional oblique collision numerical model was used to reveal the metal jet behavior and interface evolution mechanism of Cu/Al and Ni/TC18 bonding interface with different density ratios,melting points,and hardness under explosive driving.The rationality was verified by comparing with experimental results and metal jet theory.This thesis includes 59 figures,4 tables,and 160 referances.