Research On The Microstructures And Mechanical Properties Of Multi-principal Elements FeCoNiCuAl High Entropy Alloys System

Compared with the conventional alloys,the multi-principal elements high entropy alloys?HEAs?not only are composed of simple phases,but also have many excellent properties such as high hardness,high strength,good abrasive resistance,good corrosion resistance and so on,therefore they have gradually become research highlights in the field of metal materials.In the paper,the effects of Al and Cu additions on microstructures and properties in the FeCoNiCuAl based high entropy alloys were investigated by XRD,OM,SEM,EDS,microhardness and compressive tests.Meanwhile,the effects of annealing temperature on microstructures and properties of the FeCoNiCuAl_0.5 high entropy alloy were studied.The results show that:?1?The FeCoNiCuAl_x?x=0.5,1.0,1.5,2.0?multi-principal elements high entropy alloys are composed of two phases of simple crystal structure,fcc and bcc.However,with the increase of Al content,the volume fraction of bcc phase increases,while the volume fraction of fcc phase decreases.The four alloys have typical dendrite microstructures.There exists distinctly Cu-enrichment in the interdendrite of the alloys,and the increase of Al aggravates segregation of Cu in the alloys.Meanwhile increase of Al content improves the yield strength and microhardness of the alloys,the FeCoNiCuAl2 alloy exhibits maximum microhardness and yield strength of 568 HV and 1435 MPa,respectively,but the plasticity of the alloys decreases with Al additions.?2?The FeCoNiAlCu_x?x=0.5,0.8,1.0,1.5?multi-principal elements high entropy alloys are composed of two phases of simple crystal structure,fcc and bcc.However,with the increase of Cu content,the volume fraction of fcc phase increases,while the volume fraction of bcc phase decreases.The four alloys have typical dendrite microstructures.There exists distinctly Cu-enrichment in the interdendrite of the alloys,and the increase of Cu aggravates segregation of Cu in the interdendrite of the alloys,but which is no change in the dendrite of alloys.Meanwhile the increase of Cu content can improve the plasticity of the alloys,the FeCoNiAlCu1.5alloy exhibits maximum compressive strain of 36.1%.But the yield strength and microhardness of the alloys decrease with Cu additions,the FeCoNiAlCu0.5 alloy exhibits maximum microhardness of 569 HV and the Fe CoNiAlCu0.8 alloy exhibits maximum yield strength of 1256 MPa.Moreover,the content of Cu has significantly influence on the fracture mode of the alloys system,it changes from cleavage fracture of the FeCoNiAlCu0.5 alloy to plastic fracture of the FeCoNiAlCu1.5 alloy.?3?The cold rolled Fe CoNiCuAl0.5 multi-principal element high entropy alloy was annealed at different temperatures.When the annealing temperature is 700-900 ?,the alloys are dendrite microstructures,and the dendrite and interdendrite of the alloys are composed of fcc phase and bcc phase respectively.However,when the annealing temperature at 1000 ?,the alloy is only consist of fcc phase,meanwhile the elements are more homogeneously distributed in the alloy,and it eliminates some part of dendrite segregation.In addition,the microhardness of alloys increases firstly and then decreases with the increase of annealing temperature,at 700 ?,the microhardness of the alloy reaches the maximum which is 418 HV,and the microhardness of annealed alloys are higher than that of the cold rolled alloy.