The Influences Of Forging And Rolling On Stuctures And Mechanical Properties Of CoCrFeNiMn

High etropy alloy are newly developed with more than 5 elements,of which the atomic percentage is 5%-35%.This kind of alloy can crystallize as a single FCC or BCC phase and have many good properties,however traditional alloy didn't have. We believe more and more high entropy alloys will be used in our daily life and in production as the technology becomes better.In our study,five normal metallic elements Fe,Co,Ni,Cr,Mn with an atomic percentage of 20:20:14:26:20 were chosen to fabricate a CoCrFeNiMn high-entropy alloy with a face-center cubic phase structure.Then we study about the microstructure and mechanical performance of this high-entropy alloy. Subsequently,effects of processing conditions such as deformation tempering on microstructure and mechanical properties were investigated.Alloy ingots of CoCrFeNiMn were fabricated using arc-melt cast.The small ingots were fabricated using induction melting furnace smelting.40% cold-rolling was operated at room temperature.The microstures,morphologies,and chemical compositions of the alloys with as-cast,cold-rolling,and heat-treated states were characterized by x-ray diffraction(XRD) and scanning electron microscope(SEM),Vickers as well as mechanical testing machine.The experimental results are as follows:1.Besides the FCC matrix structure,existence of a small amount of secondary phase with a composition of Cr2Mn,which is formed in a needle shape.The Cr2Mn phase was found to be stable in CoCrFeNiMn high-entroy alloy.2.The as cast CoCrFeNiMn high entropy alloy possess a good strength and deformation capability. At a low temperature, the tensile strength increase with a decreasing temperature.At room temperature the breaking strength of HEA(high-entropy alloy) is 403 MPa, while the breaking strength doubled to 867MPa at -196?; At a high temperature, material strength and toughness decrease with a increase temperature. It can be seen from the fracture that the fracture has changed:During the stretching process,the materials varying degrees of ductile fracture. At low temperature, the tensile properties are good, at 700? and 800? the dimple becomes very shallow, the elongation decreased.3.Alloys are face-centered cubic solid solution structure before and after deformation. The as cast is sample typical feature of the dendrites, alloy grains and dendrites distance after cold deformation are small, help to improve the strength of the material.4.At room temperature,the performances of HEA are as follows:The microhardness of cast is 190HV, the breaking strength is 403MPa, the elongation is 65%;The microhardness of forged alloys 211HV, breaking strength is 563MPa, elongation is 65%; The microhardness of the alloys after rolling the alloy hardness 345HV increase 81.3% over cast one, breaking strength reached 1060MPa, increase 163.1% compared to the as-cast.