Effect And Mechanism Of Pulsed Magnetic Field Treatment On The Microstructure And Mechanical Properties Of 20Cr2Ni4A Steel

With the gradual increase in the performance requirements of engineering applications,traditional material processing technology has limited control over the processing process,and the instability of the improvement of material performance limits the further development of material processing technology.As early as the 1950 s and 1960 s,the magnetic field was introduced into the field of material processing.In recent years,the combination of magnetic field and traditional material processing technology has become increasingly close.Pulsed magnetic field is used to improve material properties due to its high processing efficiency,low temperature rise,environmental protection and pollution-free advantages.In this paper,the influence of pulsed magnetic treatment on the microstructure and mechanical properties of20Cr2Ni4 A steel is studied,and the distribution of the magnetic field and the stress and strain of the material during the pulsed magnetic treatment are studied through finite element analysis.Finally,the influence mechanism of pulsed magnetic treatment on the material is explored.The results of this research are as follows:(1)Design and build a pulsed magnetic treatment system according to experimental requirements,apply 1 T,4 T,9 T pulsed magnetic treatment to the material,and perform 5,10,and 20 pulsed magnetic treatments on the material under different magnetic field strengths.(2)Analyze the metallographic and Fe-C phase changes of 20Cr2Ni4 A steel before and after pulsed magnetic treatment with different magnetic field strength through metallurgical microscope and EBSD data;use XRD data to calculate and analyze the changes in dislocation density,and further observe the dislocation structure through TEM;through MFM Characterize magnetic domains and study the effect of pulsed magnetic treatment on the structure and distribution of magnetic domains.(3)By measuring the microhardness,yield strength and residual stress,the mechanical properties of 20Cr2Ni4 A steel before and after pulse magnetic treatment with different process parameters were quantitatively studied.The results show that20Cr2Ni4 A steel has better mechanical properties after pulse magnetic treatment.With the increase of magnetic field strength,the microhardness also increases,and the hardness distribution range is more concentrated and uniform;pulse magnetic field treatment makes the yield strength of 20Cr2Ni4 A steel limited increase,and the elongation after fracture the improvement makes the toughness of the material more excellent;different magnetic field treatments reduce the average residual stress of the material,and the distribution range of the residual stress is reduced.(4)The pulse magnetic processing system model is established through finite element simulation,and the distribution of the magnetic field and the stress and strain of the material during the pulse magnetic processing are studied;the magnetostrictive effect and the dislocation Frank-Read source mechanism are combined to perform the pulse magnetic processing.Material dislocations proliferate and diffuse,dislocation density increases and dislocation distribution is more uniform,and other dislocation structure change processes are analyzed,and the energy influence mechanism of pulsed magnetic treatment on the structure and properties of 20Cr2Ni4 A steel material is summarized.