Research On Modification Of AlCoCrFeNi_2.1Eutectic High-Entropy Alloys By Special Processing Processes

High-entropy alloys(HEAs),multi-principal-element alloys(MPEAs),is a new type of alloy and has five or more major elements,ranging from 5 to 35 at%mixed at equimolar or near-equimolar ratios.The multi-principal-element character of HEAs leads to some important effects,these can be considered as four core effects,including:(1)high-entropy effect,(2)severe-lattice-distortion effect,(3)sluggish diffusion effect,(4)cocktail effect.Because of the unique effects,HEAs is expected to form single-phase solid solutions and possess some excellent properties that are not seen in conventional alloys.In our study,AlCoCrFeNi2.1 eutectic high-entropy alloys(EHEAs)with the FCC and B2 phase structure was prepared by arc melting.The EHEAs was deformed by ceramic rolling with 23.06%reduction in thickness and ceracon with various reductions:9.15%,18.31%,25.20%,31.57%and 47.23%.The EHEAs with reduction of 23.06%was isochronally annealing for lh at 400 ? and 800 ?,respectively.The effect of plastic deformation on the microstructure and mechanical properties of the AlCoCrFeNi2.1eutectic high-entropy alloy was investigated by scanning electron microscopy,X-ray diffraction,compressive and hardness tests in order to obtain the propose.The experimental results show that:The ceramic rolling technique greatly enhanced the strength of The AlCoCrFeNi2.1 EHEAs and optimize the the strength-ductility combination,with the thickness reduction of 23.06%,The microhardness,yield strength and ultimate compressive strength of the as-cast sample are 301HV,557.09 MPa,1747.663 MPa,respectively.And the as-rolled EHEAs exhibited a large increase in microhardness,yield strength and ultimate compressive strength(424HV,1611.42 MPa and 2212.991 MPa,respectively),and remained the plastic strain of 28.36%.The ductility of the prepared by ceramic rolling and annealing improved obviously.At 400 ? and 800 ?,the plastic strain was 33.72%and 38.54%,respectively.And the microhardness of the EHEAs annealed at 400 ?(446HV)is much higher than the as-rolled EHEAs,the microhardness of the EHEAs annealed at 800?(337HV)is much higher than the as-cast EHEAs,while is much lower than the as-rolled EHEAs.In addition,AlCoCrFeNi2.1 EHEAs annealed at 800 ? has a large number of equiaxed crystals instead of lamellar grain and the fracture mode from cleavage/quasi-cleavage fracture of the as-rolled EHEAs change to the ductile fracture of the EHEAs of annealed at 800?.The ceracon technique greatly enhanced the mechanical properties of The AlCoCrFeNi2.1.EHEAs.The results revealed that AlCoCrFeNi2.1 prepared by ceracon with the thickness reduction of 47.23%and the yield strength(1444.69MPa)was enhanced 1.5 times than in the as-cast condition,the compressive strength was 2301.29MPa,increased by 35%compared to the as-cast condition.AlCoCrFeNi2.1 remains the plastic strain of 23.56%.With the increase of deformation,the lamellar grains in AlCoCrFeNi2.1 EHEAs was elongated along the direction of stress and the microstructure tend to homogenize.Ceramic particles hindered the plastic deformation during the pressing process.The inner grains of the EHEAs of the pressing without ceramic particles were much more broken than those of the EHEAs of the pressing with the addition of ceramic particles.In addition,the strength and hardness of the EHEAs of the pressing with the addition of ceramic particles at a relatively small reductions(18.31%)is equal to that the EHEAs of the pressing without ceramic particles at a large reductions(47.23%),and the EHEAs with 18.31%reductions have a good ductility.