Simulation Of Mechanical Properties Of High Entropy Alloy Materials Based On Crystal Plasticity Finite Element

High-entropy alloys(HEAs)often offer high strength,good toughness,corrosion resistance,and radiation resistance,and its multi-principal element design concept of HEAs provides a broad space for the research and development of alloy.The excellent mechanical properties of HEAs are closely related to their microstructure and microscopic deformation mechanism.Therefore,the research on the correlation between micro-mechanism and macro-mechanical properties is of great significance for understanding the mechanical behavior of materials and optimizing their properties through microstructure design.In this work,the micro-deformation mechanism of HEAs is formulated into the constitutive relationship through internal variables,and the mechanical properties of HEAs are simulated by crystal plasticity finite element method(CPFEM).The main research results are as follows:1)Crystal plastic constitutive model for HEAs is developed,in which an equal volume partition model is proposed to simulate the grain refinement due to twinning and the Hall-Petch formula is applied,to consider the size effect in modeling the HEAs.On the platform of ABAQUS,the crystal plastic constitutive model is coded as VUMAT subroutine,and the secondary programming of CPFEM is realized.2)By CPFEM,the mechanical behavior of HEA Al_0.1Co Cr Fe Ni under three different annealing conditions are investigated.Numerical results are in good agreement with experiments,and the reliability and applicability of the developed crystal plasticity constitutive model and the coded subroutine VUMAT are verified.Our study shows that there exists a competitive relationship between dislocation slip and twinning mechanism and the two mechanisms work together when the stress is large.Due to deformation compatibility,the triggering time and evolution rate of the dislocation slip and deformation twinning in unrecrystallized and recrystallized grains are different,which is a complex coupling process.The study also shows that the dislocation slip and twin deformation increase the capability of the material to generate plastic deformation and increase the toughness of the material,while the entanglement of dislocations and twin boundaries blocking dislocation slip would strengthen the material.The two factors provide the answer for the question:why the studied HEA has high-strength and high-toughness properties under 873K annealing conditions.3)CPFEM is performed to simulate the mechanical properties and texture evolution of the HEA Co Cr Fe Ni,and the dependences of mechanical properties on the initial textures are investigated.Simulation results for the model with initial random texture are in good agreement with experimental results.The relative errors of key indicators such as yield strength,ultimate strength,elongation,et al.are less than 5%,which again shows that the established crystal plastic constitutive and the developed program are feasible and reliable.The study of texture dependence in our models demonstrated that,the texture has great influence on the strength of HEAs whereas little effect on the ductility.Due to the grain rotation,both the strong texture and no texture of polycrystalline shows the trend to transform to relative weak texture under simple tension.In summary,the mechanical behavior of HEAs is closely related to microstructure parameters such as grain size,dislocation density,deformation twins,and crystal texture.The microstructure design by adjusting"rolling+annealing"fabrication technique offers a feasible way to develop high-performance HEAs.The work in this paper could provide theoretical guidance for the design.