Research On Microstructure Forming Mechanism Of High Entropy Alloy By Selective Laser Melting Manufacturing

High entropy alloy is a new type of metal material that has received wide attention.It is composed of four or more atoms in equal or nearly equal proportions.It has outstanding advantages,such as great mechanical properties,high oxidation resistance and high corrosion resistance,have very broad application prospects.High-entropy alloys are rapidly developing and still have many problems in actual industrial production.For example,the current preparation methods of high-entropy alloys are relatively limited.The products are small in size and high in costs.These problems limit the application of high-entropy alloys in complex systems and precision manufacturing.In order to solve this problem,we focus on the technical field of additive manufacturing,especially the selective laser melting(SLM)technology.SLM technology is a new type of metal additive manufacturing technology that has attracted much attention.It uses high-energy laser as the energy source.It has the advantages of high processing accuracy and excellent mechanical properties.SLM is developed and improved from laser selective sintering technology(SLS).While retaining the advantages of SLS technology,it greatly increases the interlayer force of the material,thereby significantly improving the mechanical properties of the material.However,defects such as pores and cracks still exist in the SLM process.At the same time,due to the small diameter of the laser beam and large local temperature changes,traditional experimental methods cannot effectively observe the evolution of the material at the microscale during the processing.Characterization and testing of the formed materials in order to infer the appropriate processing parameters,which limits the promotion and application of SLM technology in new materials.Therefore,in order to further expand the application of high-entropy alloys,this paper compares and analyzes the effect of the process parameters on the microstructure of the material,along with the characteristics of the material in terms of surface morphology and microstructure evolution.Through various researches and explorations,certain explorations have been made for the development of high-entropy alloys in the field of metal additive manufacturing.This paper first proposes a molecular dynamics simulation model of selective laser melting technology.By reproducing the melting and solidification process of powder under the heat of laser on a micro-scale,the surface morphology,dislocation distribution,and defect nucleation during processing are analyzed.The influence of laser energy density and laser scanning speed on the quality of material forming on the microscopic scale was further explored.Secondly,starting from the most basic solidification process in the SLM process,the problem of grain nucleation and growth during the solidification of high-entropy alloys was explored.The microstructure of the material under different cooling rates,including pure crystal structure,pure amorphous structure and amorphous/crystalline composite structure are formed in MD simulation.Finally,in view of the various complex crystal and amorphous structures that appear during solidification,a composite structure model with different amorphous ratios is established.By adjusting the thickness of the amorphous layer,using methods including simulated tensile experiments,a comparative analysis of the composite structure was carried out.The influence and law of the ratio on the deformation behavior of the material were also summarized,which improved the understanding of the crystalline/amorphous composite structure.