| It is the first time to prepare high-entropy alloy by thin strip casting-rolling process.Compared with the traditional process of preparing high-entropy alloy,it has the characteristics of Sub-Rapid cooling and near-final forming.It is a new method of preparing high-entropy alloy with high efficiency,energy saving and low cost.In this part,as-cast Al0.3CoCrFeNi,Al0.4CoCrFeNi,AlCoCrFeNiNb0.3 strips with thickness of 1.5mm,1.5mm and 2.0mm were prepared by thin strip casting and rolling process.The as-cast,annealed microstructures,properties and texture evolution of the three strips were studied and discussed.Through thermodynamic calculation and phase diagram calculation method,the budget analysis of alloy composition before the experiment is realized.From the point of view of the structure and properties of as-cast and annealed alloys,the advantages of thin strip casting-rolling process for preparing high-entropy alloys are analyzed,and the texture evolution of as-cast and annealed alloys in thin strip casting-rolling process is mainly studied.The as-cast Al0.3CoCrFeNi,Al0.4CoCrFeNi and AlCoCrFeNiNb0.3 produced by thin strip casting and rolling process are discussed,including the calculation of phase diagram before experiment,the structure,phase,texture and the testing of tensile properties at room temperature.The results show that the structure of Al0.3CoCrFeNi and Al0.4CoCrFeNi high entropy alloys prepared by thin strip casting and rolling process is two regular columnar crystals.The columnar crystals grow from the surface to the core until they converge,and the grain boundary is clear and straight,which is a single FCC phase.The structure of AlCoCrFeNiNb0.3 shows two equiaxed zones and the surface is equiaxed.Compared with the average grain size of the same.high-entropy alloy prepared by the traditional method,the casting-rolling process can refine the grain size;The yield strength and tensile strength of Al0.3 alloy at room temperature are 218.4MPa,491.8MPa and 99.6%respectively.Compared to traditional method,the yield strength of Al0.3 alloy increases by 9.2%,the elongation after fracture increases by 3.1%,and the tensile strength is the same.The yield strength of Al0.4 alloy at room temperature is 263.5MPa.The tensile strength is 561.0MPa and the elongation after fracture reaches 67.8%.Compared to traditional method,the elongation after fracture increases by 23.7%.The yield strength and the tensile strength are equivalent.After cold rolling and annealing at 900℃,the microstructural orientation of as-cast Al0.3 alloy shifts from(310)(210)to(110)of annealed Al0.3 alloy.With the prolongation of annealing time,the(110)orientation of deformed Al0.3 alloy begins to flow to(111)orientation of sub-crystalline Al0.3 alloy.The(110)orientation is easy to form brass deformation texture,including Bs {110}<112>texture and Goss {110}<001>texture remaining in recrystallized structure.After cold rolling and recrystallization annealing at 1000℃,the microstructural orientation of as-cast Al0.4 alloy shifts from as-cast(311)orientation to recrystallized(110)orientation.The bulk sub-crystal structure region almost presents(111)orientation and(112)orientation,and(112)orientation grains may flow from(110)orientation to(111)orientation through(111)orientation.(110)Orientation tends to form brass-like deformation texture,including Bs {110}<112>texture and Goss {110}<001>texture remaining in recrystallized structure,(112)Orientation tends to form Copper {112}<111>texture remaining in recrystallized structure.After annealing at 1000℃ for 60 min,the texture of BCC in cold rolled Al0.4 alloy is in a slow dispersion state,and there is no obvious strong texture.The main reason is that BCC nucleates preferentially at the grain boundary of FCC phase without preferential orientation.At Φ2=0 degree,there are weak fiber texture {210}<001>texture and maximum orientation density f=0.6,in which fiber texture<001>RD.There are two weak fiber texture {001}<110>texture and maximum orientation density f=1.7,in which the texture of fiber<001>is parallel to ND.After annealing at 1000℃ for 180min has strong texture of BCC phase.When(φ2=0°,the texture {210}<001>of fibers existed before increases in texture strength,and the maximum orientation density f=8.1;the texture {001｝<110>of lambda fibers existed before increases in texture strength,and the maximum orientation density f=15.2.Generally speaking,the advantages of preparing high-entropy alloy system by thin strip casting and rolling are obvious,the grain size of the prepared high-entropy alloy system is refined,the comprehensive mechanical properties are improved,and the texture evolution law is distinct from that by vacuum arc melting.The purpose of preparing high-entropy alloy system by a new method is achieved. |
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