Temperature And Crystalline Orientation-Dependent Plastic Deformation Of High-Entropy Alloy By Molecular Dynamics Simulation

This paper uses the molecular dynamics(MD)method to study the temperature and grain orientation-dependent plastic deformation process of high entropy alloys(HEA).Firstly,the effect of temperature on the microstructure and mechanical properties of FeNiCrCoCu high entropy alloy under uniaxial tensile and compressive strain was studied.Then,the effect of crystal orientation on the plastic deformation of FeNiCrCoMn high entropy alloy was also studied.The calculated static characteristics of both HEAs are consistent with their respective experimental/early theoretical results.The calculation of the high entropy alloy FeNiCrCoMn shows that the compressive yield stress of the single crystal<001>/polycrystalline is consistent with the experimental results in terms of magnitude.The yield stress and Young’s modulus of FeNiCrCoMn high entropy alloy single crystals exhibit strong directional dependence.The stress of its polycrystalline structure is independent of Young’s modulus and crystal orientation,and it has strong ductility.Calculations have found that FeNiCrCoCu and FeNiCrCoMn high entropy alloys generate a large number of dislocations during plastic deformation,with 1/6<112>Shockley dislocations accounting for the highest proportion of total dislocations due to their mechanical stability.As the temperature increases,the thermal motion of atoms intensifies,promoting the slip and annihilation of dislocations.As the temperature increases,the strain value corresponding to the initial plastic deformation decreases,and the initial strain corresponding to the occurrence of 1/6<112>Schockley dislocation also gradually decreases.The number of dislocations generated under normal stress loading is much greater than that generated during the shear process.During the elastic deformation stage,the transformation from the FCC phase to the HCP phase and other crystal phases hardly occurs until stress yielding occurs.As the temperature increases,the yield stress,yield strain,and Young’s modulus of high entropy alloys gradually decrease.Young’s modulus of single/double crystal FeNiCrCoMn high entropy alloys varies greatly under compression and tensile loads,while the difference in polycrystalline alloys is very small.It was found that the yield stress/strain,FCC-HCP phase transition,and strain corresponding to the slow to fast increase in dislocation density of high entropy alloys are consistent.At the temperature under consideration,the magnitude of the strain at this strain point gradually decreases as the temperature increases.After crossing the strain transition point,the yield stress,FCC-HCP phase transition,and dislocation density all rapidly increase.In summary,temperature and crystal orientation can affect the generation and evolution of dislocations and phases in high-entropy alloys,thereby affecting the mechanical properties of high-entropy alloy materials.