Development Of Gradient Nanostructured Plate Fabrication Device And Property Charaterization Of 316L Stainless Steel

Although the nanostructured metal material has the characteristics of high strength and high hardness,its plasticity is poor.The poor plasticity has also become a bottleneck in the application of nanostructured metal materials.Gradient nanostructures were obtained by multistage construction of nanostructures.If the metal material has a gradient nanostructure,the strength and plasticity can be matched.So how to prepare gradient nanostructures in metallic materials has become a technical problem that must be solved.For the metal plate components,most of the current gradient nanotechnology and equipment have some shortcomings.Based on this background;this paper proposes a new type of gradient nanocrystallization process,which is called Double-sided symmetrical rolling treatment(DSRT).At the same time,based on the DSRT process,a mechanical device was built to prepare a symmetric gradient nanostructure layer on both sides of the metal plate.The main work of this paper includes the following parts:Determine the overall design of the metal plate DSRT equipment.The components of the device include a transmission,a rolling processing device;a lateral feed device,a circulating cooling device,and a power source.The transmission is driven by a power source.During a motion cycle,it drives the metal plate sample for uniform linear motion.The rolling processing device remained stationary during this period,and the surface of the metal plate was rolled and an indentation was generated.Thereafter,the lateral feed device controls the feeding of the rolling processing device,repeating the above process and generating a new indentation during the new motion cycle.This indentation partially overlaps the front indentation.The constantly overlapping indentations create a rolled area on the surface of the metal plate.Multi-pass DSRT processing is performed and the processing pressure is uniformly increased from pass to pass,eventually achieving gradient nanocrystallization of the metal plate.During the processing,the circulating cooling device in the equipmenteliminates the heat generated by the continuous friction between the rolling processing device and the metal plate.Debug the metal plate DSRT equipment.The commissioning work includes determining the movement period,the moving speed of the transmission device and the number of feeds of the rolling processing device by experiment.Then programming the machining feed program.The rolling pressure of the rolling processing device was measured.The size of the roller and the anti-bending scheme were determined.A large number of DSRT experiments were performed on the 316 L stainless steel plate on this equipment.The influence of processing pass and processing feed rate on the surface quality of the sample was explored.Finally,the DSRT processing plan of 316 L stainless steel plate was determined.Performance characterization of DSRT-316 L plate samples includes surface roughness measurement,metallographic observation,quasi-static tensile test and hardness test.It was found that the roughness Ra of the DSRT-316 L plate sample was20.8 nm,which was much lower than that of the mother plate sample.It was observed that the internal grain size of the DSRT-316 L plate sample increased from the surface to the inside gradually,showing a gradient distribution.In the hardness test,the DSRT-316 L plate sample obtained by 7 passes and 15 ?m feed rate processing has a surface hardness of 460 HV and a core hardness of 260 HV,and the hardness of the mother plate test is 190 HV.In the tensile test,it was found that the yield strength(565MPa)of the DSRT-316 L plate sample obtained by processing 9 passes and 15 ?m feed rate processing was higher than the mother plate sample(248 MPa),and the tensile strength(766 MPa)was also higher than that of the mother plate sample(602MPa),the elongation was kept at about 41%.