Study On Deformation Behavior Of FeCrCoNiMo_x High Entropy Alloys

High entropy alloys are defined as a new kind of solid solution alloy,which consists of five elements and the atomic percentage of each component is between 5%and 35%.High entropy alloy is considered as a new type of structural and functional materials for a wide range of potential applications.In the present work,FeCrCoNiMo_x（x=0,0.1,0.3,0.6）high entropy alloy was prepared by vacuum arc melting furnace and used as the research object.The influence of Mo with large atoms radius on crystal structure,microstructure and mechanical properties were discussed and the variation of microstructure and properties with composition was clarified.In addition,bases on the isothermal compression tests,the hot deformation and dynamic recrystallization behavior of the alloy were investigated,the relationship between processing map and microstructure evolution was carried,so as to determine the optimal thermal processing parameters.The main conclusion of the research as follow:（1）The influence of Mo element on the microstructure,crystal structure and mechanical properties of the alloy was determined by observing the structure and crystal structure of the alloy and measuring mechanical properties:with the increase of Mo content,the microstructure of the alloy changes gradually from single phase FCC centered cubic solid solution structure to FCC+σphase and FCC+σphase+μphase.the microstructure of the alloy also gradually changed from uniaxial crystal to dendrite,and the hardness of the alloy changed with the change of the alloy microstructure.FeCrCoNiMo_0.6alloy has the highest hardness,reaching 375 HV.（2）High temperature compression experiments show that the peak stress of FeCrCoNiMo_0.3 high-entropy alloy increases with the decrease of deformation temperature and the increase of strain rate.The thermal deformation activation energy of the alloy was calculated by Arrhenius equation with Zener-Hollomon parameter,which was 411.58k J/mol,stress exponent n=3.37673.（3）The processing map base on Prasad criterion indicate that the flow instability zones for FeCrCoNiMo_0.3 high entropy alloy in the region of T=950-1150℃,ε=10.-1s should be avoided.The optimum thermal processing range of FeCrCoNiMo_0.3high entropy alloy is T=1150-1250℃,ε=10^-2.25-1s^-1,and efficiency power dissipation in this region is 33%-41%.The crystal structure of FeCrCoNiMo_0.3high entropy alloy has not changed after thermal deformation process,and FCC is still the main component.The deformed structure mainly shows that the dendrites are elongated and recrystallized grains are formed around the grain boundary.with the increase of deformation temperature and the decrease of strain rate,the dynamic recrystallization phenomenon becomes more and more obvious,the crystal tends to be anisotropic and the microstructure is more uniform.