Reserch On Microstructure And Mechanical Properties Of FeCrCoNiAl Series High Entropy Alloys

High-entropy alloys,now it's also called multi-principal alloys,which were prepared by mixing four or more than four elements in equal proportions or nearly equal proportions.In recent years,they have draw much attention to scholars.The research field of high-entropy alloys was also more and more extensive,such as corrosion resistance,anti-fatigue,anti-radiation and anti-oxidation properties,which of the most researched is that the structure and performance of the alloys.In this paper,based on the typical AlCoCrFeNi high-entropy alloy,two series of high-entropy alloys that Fe₃CrCoNi Al_xand Fe₃Cr₂CoNiAl_xwere designed by increasing the Fe element content and adjusting the Cr element content.At the same time,the amount of Al element was adjusted to change the value of x in Fe₃CrCoNiAl_xand Fe₃Cr₂CoNi Al_x.Furthermore,their law of performance change and structure evolution were analyzed systematically in these two systems.The results of the study showed that the hardness of the Fe₃CrCoNiAl_xalloys and Fe₃Cr₂CoNiAl_xalloys increased with the increase of the Al element content,and the compressive yield strength and fracture strength also increased,but the compression plasticity becomes worse.The Vickers hardness increased from 156 HV_0.1to 521 HV_0.1,the compressive yield strength increased from 148 MPa to 1299 MPa,and the Plastic deformation was reduced to 22.5%.Among them,Fe₃CrCoNiAl_0.9alloy has the best comprehensive.The characterization of the structure morphology showed that the volume fraction of the FCC phase at the dendrites in the alloy structure gradually decreased until it disappeared.In the dendrites,the volume fraction of BCC/B2 phase between dendrites gradually increased,and the particle size of the B2 precipitate phase became smaller.The results of nanoindentation analysis showed that the hardness of the BCC phase was nearly twice than that of the FCC phase.Therefore,it can be seen that the hardness and strength increment could be attibuted to the increased BCC/B2 phase.In comparison with the Fe₃Cr₂CoNiAl_xand Fe₃CrCoNiAl_xwith different Cr content,the variation of the Cr content on microstructure and mehcanical behavior was explored.The results showed that there were two scales of B2 phase,s-B2 phase(20-50 nm)and m-B2(200-300 nm)phases distributed in the Fe₃Cr₂CoNiAl_x.It mainly attibuted to the multi-scale precipitation strengrhnening.Increased by nearly 17%,the yield strength of Fe₃Cr₂CoNiAl_1.2alloy can reach 1464 MPa,thus the increase of Cr element content can strengthen the mechanical performance of the alloy.