| With the improvement of modern production technology,cold rolled stainless steel plate is used more and more widely,the requirements of the user for the quality of cold rolled stainless steel strip in flatness is also more and more high.In China,the consumption structure of stainless steel is mainly plate-based,while during the cold-rolling process of the plate,the material will be plastically deformed,leading to a very obvious work hardening phenomenon,which will have a great impact on the performance of the product.The most obvious phenomenon is that the stamped product is extremely susceptible to cracking.As a new surface modification technology,High-Current Pulsed Electron Beam(HCPEB)can act on the surface of materials to change the surface microstructure and even the compositions of the material,such as grain refinement,which could improve the hardness and wear resistance or corrosion resistance of the material.As a result,improving the overall performance of the material and extending the life of the workpiece.This project was supported by the national natural science fund “Performance distribution regulation and service behavior of multi-component thermochemical treatment on FGM coated gear”(code: 51575073).The 304 austenitic stainless steel was selected as the matrix material,Cold rolling combined with high current pulsed electron beam technology,and then the microstructures and mechanical properties were studied by electron backscatter diffraction(EBSD),scanning electron microscopy(ECC),X-ray diffraction(XRD)and other techniques.The main work of the thesis is as follows:(1)the samples of cold-rolling after solution treatment was carried out to study the microstructure,texture and phase evolution of the samples under different shape variables.(2)Irradiation of high-current pulsed electron beams under different parameters(22kV,5 times;17kV,5 times)for samples with different deformations,study the microstructure,texture and phase evolution of the samples.(3)The recrystallization mechanism of the alloy was clarified based on the in-situ observation.Finally,the hardness,corrosion resistance and friction and wear properties of each sample were compared by performance experiments.The purpose was to improve the comprehensive properties of 304 austenitic stainless steel.Through the experiments and analyses,the main conclusions are as follows:(1)After the 304 austenitic stainless steel cold rolled at room temperature,the deformation induced martensite transformation will occur in the microstructure of the sample.As the deformation increases,the martensite content increases gradually and the crystal grains gradually appear fibrous and texture in the sample.(2))Craters are formed on the surface after electron beam treatment,and the undeformed sample grains and grain boundaries did not change significantly,and no phase change occurred.(3)After the electron beam modification of the deformed material,the deformation-induced martensite transform to austenite in the microstructure,and different degrees of recovery and recrystallization occur at the austenite grain boundaries and shear zones,formed nano-scaled recrystallized grains.At the same time,the appearance of equiaxed grains can effectively weaken the texture strength,reducing the anisotropy of the alloy.(4)The in-situ test indicates that the recrystallization mechanism during the electron beam irradiation of the cold rolled deformation specimen is mainly the nucleation growth of the prior austenite and the new austenite.(5)Properties test analysis found that the hardness of the material is positively correlated with the martensite content or deformation.After electron beam treatment,the hardness of the material will decrease as a whole.The recrystallization process and the degree of work hardening are the main reasons.The corrosion and friction and wear properties of the cold rolled samples after treatment with different electron beam parameters will be improved to a certain extent. |
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