| The increasing demand of lightweight design production often need to use different materials to meet the standards of strength,lightweight and impact performance.The composite structure of aluminum alloy and stainless steel can give full play to the inherent properties of two materials,reduce structure's weight and extend the function of parts and increase the fatigue life of parts and reduce the use of rare precious metals.It has a high potential applicat ion in traditional industrial manufacturing.Based on the numerical simulation to guidance the experiment,the deformation in process of magnetic pulse joining(MPJ)and the influence of metal surface coating are analyzed in this study.Through the finite element analysis software ANSYS,the accelerated motion of aluminum alloy and stainless steel in the deformation process of MPJ is analyzed.The influence of different process parameters,discharge voltage radical gap and the position of lap pipe,which have effects on joint,is analyzed to get the law of influence which could contact the process of MPJ.The reseach also ananlyze the deformation behavior of interface in the process of impacting by smoothed particle hydrodynamics(SPH)method,exploring the formation mechanism of interface in MPJ.The inner tube of the joining pipe is electroplated,and the magnetic pulse joining of 3A21 alloy and 304 stainless steel tube is completed.Using 20 steel tube instead of stainless steel tube,plating nickel and copper on the surface of 20 steel tube,the influence of different coating on joining length is observed and studied via the microscope.The preliminary experiment of 3A21 aluminum alloy tube and stainless steel pipe found that the axial accuracy of tibe's overlap has great influence on the uniformity of tube's connection,the poor axial accuracy will lead to the phenomenon of uneven connection area.The phenomenon of uneven connection area has been improved obviously through the design of specific experimental setup increasing axial accuracy,resulting of good stripping performance.The morphology of interface is observed via optical microscope,measuring the connection length found that the nickel surface coating can improve the connection length(44%)of sta inless steel and aluminum alloy effectively while the connection length of 20 steel is promoted restrainedly.Using SEM to observe the morphology of the interface of different suface coating found that the interface have two different appearance: the inter face with transition zone and the interface without the transition zone.The analysis of the interface with transition zone found that the interdiffusion of elements between two materials happened and the width of the diffusion area was about 20 ?m.Combined with numerical simulation,interface with a transition zone is analyzed,finding that the phenomenon of the spread of the elements occurred in the transition zone.Combining with numerical simulation,the formation of the microstructure defects related to “jet” created by interface contact,and the interface state in the instant of impact of “high temperature”,“high pressure” is one of the important reasons leads to the formation of a wavy appearance. |
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