The High Temperature Plastic Deformation And Numerical Simulation Of AlCoCr_0.5FeNiTi_0.5 High Entropy Alloys

High entropy alloys have good mechanical,physical and chemical properties such as high hardness,high strength,wear resistance and corrosion resistance.Thus,they have broad application prospects in modern engineering.However,due to the low plasticity of some high entropy alloys under high temperature deformation,and after high temperature forging,the alloys prone to cracking,large scale engineering applications of high entropy al oys are greatly limited.In view of this,the project takes AlCoCr_0.5FeNiTi_0.5 as the research object.The influence of the stress and strain condition on the crack formation mechanism of high entropy alloys is studied by applying the package.Combined with the finite element simulation,the effective control of high entropy alloys'high temperature crack is realized through the optimization of the structure of the sheath.AlCoCr_0.5FeNiTi_0.5alloys after high temperature compression 40%deformation do not appear obviously cracking.It provides a useful reference for the modification of high entropy al oys.Firstly,according to the theory of plastic mechanics,the high temperature deformation process of AlCoCr_0.5FeNiTi_0.5 high entropy alloys are analyzed.An effective analysis model of equivalent canned forging is established,and the calculation formula of deformation force of AlCoCr_0.5FeNiTi_0.5 high entropy alloys and the limiting wall thickness of AlCoCr_0.5FeNiTi_0.5 high entropy al oys are given.This study is conducted under conditions which the package thickness is 1mm,2mm,3mm,4mm,and the deformation temperature is 1000?,1050?,1100?,and strain rate is 0.1s^-1,1s^-1,10s^-1.The aim is to study the effects of different deformation conditions on crack initiation,microstructure and mechanical properties.It shows that with the increase of package thickness,the increase of temperature,the microstructure of dendrite becomes smaller and smaller.The grain size of the alloy is relatively small when the strain rate is 1s^-1.When the deformation temperature is high,the flow stress is small,and the high-entropy alloy is more prone to plastic deformation.In addition,the larger the deformation rate,the greater the flow stress of the alloys.The increase of the wall thickness can improve the stress state in the deformation zone.The increase of the spherical stress has an inhibitory effect on the crack.Meanwhile,the distribution of equivalent stress,equivalent strain and damage degree of high entropy alloys under different package thickness,deformation temperature and strain rate are simulated by Deform software.Simulation results show that when the wall thickness increases,the damage degree of the material decreases.Considering the lattice distortion of high entropy alloys is serious,C&L ductile fracture criterion is selected to analyze AlCoCr_0.5FeNiTi_0.5 high entropy alloys'canned forging damage.And the deformation temperature has little effect on the damage degree in the deformation temperature range from 1000?to 1100?,which is consistent with the experimental results.