Study On The Structure And Properties Of FeCoCrNi Five Element High Entropy Alloys

High entropy alloys have received much attention because of their unique properties.In this paper,the effects of different elements on the organization and properties of FeCoCrNi high entropy alloys are studied.Mo,Ti,and Zr metal elements were added to this alloy to form the FeCoCrNi X（X=Mo,Ti,Zr）five-element high entropy alloys.To find out how the alloying elements affect the types of major intermetallic compounds in the FeCoCrNi high entropy alloy.We studied how different intermetallic compounds affect the corrosion resistance,compressive mechanical properties and magnetic properties of high entropy alloys The high entropy,slow diffusion effect makes the high entropy alloys have excellent thermal stability,so we explored the differences in phase stability and mechanical properties of the alloys at different annealing temperatures.（1）FeCoCrNi Mo alloy shows a typical dendritic structure.FeCoCrNi Ti alloy has many long strips between the dendrites,which are composed of（Ni,Ti）rich phases.The FeCoCrNi Zr alloy shows dark dendrites with a lamellar structure,and the morphology shows a typical sub-eutectic structure.FeCoCrNi Mo alloy consists of face-centered cubic phase,σphase andμphase multiphase.The FeCoCrNi Ti alloy consists of face-centered cubic phase and phase structure.The body-centered cubic phase and C15 Laves phase are detected in FeCoCrNi Zr alloy.The main intermetallic compound phases of FeCoCrNi X（X=Mo,Ti,Zr）five-membered high entropy alloy belong to topologically dense row phases.（2）Among the three FeCoCrNi X（X=Mo,Ti,Zr）five element high entropy alloys,the addition of Mo element has the greatest effect on hardness.The solid solution strengthening and fine grain strengthening caused by the addition of Mo elements were higher than those of Zr and Ti elements.The compressive strengths of FeCoCrNi X（X=Mo,Ti,Zr）five-membered high entropy alloys were 2023.5MPa,1001.1MPa,and531.2MPa,respectively.The fracture mechanism of FeCoCrNi Mo alloy is brittle fracture along the crystal and deconvolution fracture.The fracture mechanism of FeCoCrNi Ti alloy is typical of decoupling fracture.The fracture mechanism of FeCoCrNi Zr alloy is brittle fracture along the crystal and decoupling fracture.In the voltage range of-0.25～1 V,no pitting potential was observed for the FeCoCrNi X（X=Mo,Ti,Zr）high entropy alloy,indicating that the alloy surface has high pitting resistance.The polarization resistance of the alloy with the addition of Ti elements was significantly higher than that of the alloy with the addition of Mo and Zr elements.FeCoCrNi Ti alloy has the highest corrosion potential,FeCoCrNi Ti alloy has the most stable passivation layer.After adding Mo and Zr elements,the alloy shows ferromagnetism,while adding Ti elements shows paramagnetism.（3）The simultaneous thermal analysis shows that the FeCoCrNi system of five element high entropy alloys has good thermal stability.The annealed FeCoCrNi Mo alloy is still composed of face-centered cubic phase andσ-phase.σphase andμphase intermetallic compounds can exist stably at 600℃.The highest microhardness value of FeCoCrNi Mo alloy is 699.96HV_0.2and the highest compressive strength is 2180.5MPa at the annealing temperature of 800℃.The FeCoCrNi Ti alloy shows the C14 Laves phase at the annealing temperature of 600℃.Some of the face-centered cubic solid solution phases were transformed intoσphase when annealed at 800℃.At an annealing temperature of 600℃,the alloy microhardness value reaches a maximum of 982.86HV_0.2,when the compressive strength reaches a maximum value of 1270 MPa.FeCoCrNi Zr alloy shows new secondary phases after annealing at 800℃and 1000℃,andσcorresponds to a lower peak strength.With the increase of annealing temperature,the Cr elements gradually deviated toward the interdendrite,and the Ni elements diffusely deviated toward the dendrite.the content of Fe,Co,and Zr elements did not change much between interdendrite and dendrite at different annealing temperatures.However,at the annealing temperature of 800℃,the content of Zr elements between dendrites was elevated because someσphases with the stoichiometric ratio of Zr Fe₃were precipitated between dendrites.The microhardness of FeCoCrNi Zr alloy reached a maximum value of 915.94HV_0.2at the annealing temperature of 800℃.The compressive strength of the alloy increased from 531.2MPa to 1164.2MPa with the increase of annealing temperature.The plasticity of FeCoCrNi Zr alloy basically did not change much at different annealing temperatures.The increase in compressive strength is the result of the combined effect of hardening of the C15 Laves phase and solid solution strengthening of the Zr atoms.Figure[34]Table[15]Reference[99]...