Application And Process Research Of Electromagnetic Pulse Treatment In CoCrFeNi(Cu/Al) High Entropy Alloy

High entropy alloy(HEA) is one of the three major breakthroughs in metallic material field in recent decades.Excellent performance that some traditional alloys cannot match,broad application prospects in extreme conditions and its unique advantages make it becomes a research hotspot in the field of metallic materials.In view of the solidification process and the final solidification structure of the alloy play a vital role in the performance of the alloy,in recent years,the electromagnetic pulse(EMP)treatment method has been applied to melting alloys,alloy solidification and heat treatment processes,and has gradually developed into a new process to improve the alloy structure and material properties.Therefore,considering of the importance of the solidification process and the solidification structure of the alloy,and the regulation effect of EMP treatment on the solidification structure of the alloy,this article focuses on the high-entropy alloy,and introduces the electromagnetic pulse treatment into the Co Cr Fe Ni(Cu/Al)HEAs.The effects of electromagnetic pulse treatment on the crystal structure,solidification structure,mechanical properties and corrosion properties of HEA in different solidification directions were studied under different process parameters.The effecting mechanisms of pulsed current and pulsed magnetic field on solidification microstructure of alloy were discussed.Results are as follows:Applying electrical pulse treatment into the solidification process of CoCrFeNiCu high entropy alloy will significantly change the macrostructure and microstructure,transforming it from a single dendrite morphology to a dendrite + quasi-equiaxed grain mixed form;It can significantly increase mechanical properties of CoCrFeNiCu,microhardness and yield strength of the alloy have been increased by 18% and 23%,respectively.At the same time,the corrosion resistance of the alloy has also been significantly improved,and the self-corrosion current has been reduced by 74%.The electrical pulse treatment can reduce the property anisotropy in different solidification directions of alloy ingots,and the improvement effect is more obvious as the pulse frequency increases.Applying electric pulse treatment to the solidification process of Co Cr Fe Ni Al high entropy alloy will significantly improve the solidification structure of the alloy,make the grains finer and uniform in microstructure;the mechanical properties of the alloy are significantly improved,the microhardness and compressive strength are increased by 39% and 12%,respectively;The electrical pulse also improves the corrosion resistance of the alloy.When the pulse frequency is 8Hz,the self-corrosion current of the alloy decreases the most,up to 58%.As the pulse frequency increases,anisotropy gradually decreases,and it almost diminished at 8 Hz.The introduction of magnetic pulse treatment into CoCrFeNiCu during the nucleation stage and all solidification stages will refine the microstructure,disturb the growth direction of dendrites,and coarsen the dendrite arms.The magnetic pulse treatment in the nucleation stage will significantly increase the(200)/(111)peak intensity ratios of the ED sample,and at the same time enlarge the directional difference of these two parameters;applying magnetic pulse treatment into the full solidification stage will reduce interplanar distance and peak intensity ratio ED direction,simultaneously reduce the alloy anisotropy.