| The influence of pulse current treatment on the evolution of material microstructure has been the focus of attention of metallurgical and materials workers.At present,researchers mainly focus on the study of grain refinement of materials by pulse current treatment,and the lack of systematic and in-depth research on the effects of pulse current applied at different solidification stages on the inclusions and matrix structure of metal materials.In this paper,pulse current is applied at different solidification stages of 303 stainless steel.With the help of metallographic microscopes,scanning electron microscopes,electrochemical workstations,and microhardness testers,the microstructure and properties of materials are analyzed.Influence of the evolution of materials and matrix tissues and discuss related mechanisms.The following experimental results were obtained:(1)Applying a pulse current at 1500?(50? above the liquidus point of the material)can reduce the size and quantity of the first type of spherical manganese sulfide,and reduce the possibility of pitting the sample,thereby improving the resistance of the material.Pitting corrosion performance.At this temperature,with the increase of the pulse current intensity,the lath ferrite in the sample can be transformed into the skeleton ferrite,and the hardness of the material is improved.(2)A pulsed current is applied at 1405?(between the solid and liquid phase points of the material).As the intensity of the pulsed current increases,the size of the chain-like MnS in the sample increases and the degree of aggregation decreases.Corrosion performance has been improved to some extent.In addition,under the action of the pulse current,the size of the clustered ferrite in the sample is reduced,and the structure is refined.(3)Applying a pulsed current at 1310?(50? below the solid phase point of the material)can suppress the growth of type I MnS inclusions,thereby reducing the size of type I MnS,and at the same time allowing subsequent formation by eutectic reaction The area of type II MnS increases.At the same time,the oscillating impact of the pulse current is conducive to the refinement of the tissue,thereby increasing the hardness of the sample.(4)When the current intensity is the same,increase the cooling rate,reduce the size of the sulfide in the sample,and improve the corrosion resistance of the sample.In addition,the increase of the undercooling degree of the sample makes the nucleation rate of the crystal grains increase,the crystal grains have no time to grow,the crystal grains are fine,and the structure is significantly refined,and the sample hardness is increased;when the cooling rate is the same,the corrosion resistance of the material And hardness,will increase with the increase of the pulse current intensity. |
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