Study On Microstructure And Mechanical Properties Of Laser Melting Deposited CrMnFeCoNi High-Entropy Alloys

Since the concept of five-equivalent equimolar ratio CrMnFeCoNi high-entropy alloy had been proposed,high-entropy alloys had been studied by more and more researchers.With the expansion of its research scope,it has been found that highentropy alloys have many excellent properties and show great potential for application.At present,high-entropy alloys are mainly prepared by "As-casting method",but due to the multiple components in the alloy system,it is easy to cause defects and composition segregation inside the materials,which limits the practical application of high-entropy alloys.It has become one of the key challenges to achieve homogenization of high-entropy alloy components with complex shapes and excellent performance.Additive manufacturing technology(3D printing)is hailed as “the most iconic production tool of the third industrial revolution”,and its rapid development has made it possible to prepare high-entropy alloy components with complex modeling performance.In this paper,the microstructure and mechanical properties of the laser melting deposited(LMD)CrMnFeCoNi high-entropy alloys have been studied.The singlewalls of CrMnFeCoNi high entropy alloy were fabricated by single direction scanning strategy and dual direction scanning strategy,and then we had compared the LMD samples with the cast samples.The X-Ray Diffraction(XRD)analyses indicate that both LMD and as-cast samples have a face-centered cubic(FCC)single-phase solid solution crystal structure.The intensities of(200)peak of the samples prepared using single direction scanning strategy with low power are much stronger,indicating an anisotropy of orientations for these samples,and with the increase of laser power,the preferential orientation becomes weak.But for the dual direction scanning samples,this phenomenon is not found.In addition,the electron backscattered diffraction(EBSD)results also show that the pole diagrams corresponding to the samples change from {100} texture to random texture with the increase of power under single direction scanning strategy.The metallographic results of the CrMnFeCoNi high-entropy alloy show that the ratio of columnar crystals to equiaxed grains in the sample can be adjusted by adjusting the process parameters and changing the scanning strategy.Besides,the phenomenon of columnar-to-equiaxed transition(CET)occurs at higher positions of single-wall samples in low power and lower positions of single-wall samples in high power.The scanning electronic microscopy(SEM)image shows that the microstructure of the as-cast sample is a coarse dendritic structure,and it can be found from EDS Mapping that the element distribution of LMD sample is more uniform than the as-cast sample.It can be found from the mechanical tensile tests that the samples prepared by the two different scanning strategy have anisotropy in the deposition direction and the scanning direction,and can gradually become isotropic through the adjustment of the process parameters.In addition,by adjusting the process parameters of the laser melting deposition technique,the CrMnFeCoNi high entropy alloys with better mechanical properties than the cast sample can be obtained.The results show that the LMD technology can adjust the microstructure and mechanical properties of the high-entropy alloys by adjusting the process parameters according to the different application requirements of the materials,and then obtain the samples with better mechanical property than the As-casting samples.The development of LMD technology provides new ideas and important insights for the preparation of high-entropy alloys with complex shapes and excellent performance,and has important research significance.