Study On Microstructure And Element Diffusion Of Shear Connection Interface Of Severely Deformed Solid Metal

In recent years,with the development of social economy,the forms of products such as space shuttles,high-speed trains and ships have become more and more complex.The plastic deformation connection technology of metal sheets has become an important means to process simple parts into complex structural parts.In this paper,the basic theory of interface bonding mechanism of shear connection technology of large deformation solid metal is studied to explore the scientific essence of plastic deformation connection of metal sheet.It not only lays a theoretical foundation for the development and application of shear connection technology for large deformation solid metal,but also contributes to the application of extended solid connection technology and the improvement of connection efficiency.Firstly,in this paper,shear connection experiments are carried out between Q345steel and Q345 steel from the same material and between Q345 steel and nickel from the different material under the condition of billets temperature of 1050?,deformation degree of 67.1%and shear rate of 12 mm/s.Connection between Q345 steel and Q345steel:the microstructure morphology and composition of the transition zone is analyzed by metallographic microscope,SEM and EDS,and the connection strength of the transition zone is tested by tensile testing machines.The results show that the transition zone is combined well and dynamic recrystallization is occured during the connection.The tensile strength of the transition zone is 300 MPa.Connection between Q345 steel and nickel:microstructure of transition zone is analyzed by metallographic microscope and SEM,content of Fe and Ni in transition zone is measured by EDS,tensile strength of transition zone is tested by tensile testing machine,tensile fracture morphology is analyzed by EDS and SEM electron microscope,and microhardness distribution of transition zone is tested by microhardness tester.The results show that the transition zone is combined well and a diffusion layer of 2?m is formed,and the tensile strength of the transition zone is 270 MPa.Then,the shear connection experiments of metal iron and nickel is carried out at the billets temperature of 1050?,deformation degree of 67.1%and shear rate of 12 mm/s.Microstructure morphology of transition zone is analyzed by metallographic microscope,SEM and TEM,and composition of transition zone is analyzed by electron diffraction pattern and high resolution.Concentration distribution curves of Fe and Ni are obtained by EDS line scanning of transition zone,and mutual diffusion coefficients of Fe and Ni are calculated.The results show that the transition zone is a high concentration zone of energy,which promotes the diffusion of Fe and Ni elements.The maximum mutual diffusion coefficients of Fe and Ni caused by heat are calculated as 1.6×10^-15 cm²/s,and the maximum mutual diffusion coefficients of Fe and Ni during shear connection are calculated as 5.4×10^-13 cm²/s.Finally,when the billets temperature is 1050?and the shear rate is 12 mm/s,the shear connection experiments of iron and nickel with deformation degrees of 50%,56%,62.9%,67.7%and 74.2%,respectively,are carried out.The thickness of diffusion layer in transition zone is measured by SEM and EDS.The results show that the thickness of relative diffusion layer increases with the increase of deformation.