Microstructure Characterization And Mechanical Properties Of CoCrFeMnNi?MoCrFeMnNi?TiCrFeMnNi High-entropy Alloys Prepared By Aluminothermic Reaction

Due to the high strength?corrosion resistance?high temperature oxidization resistance and other excellent performances,high-entropy alloy stirs widely attention and research.High entropy alloy is mostly prepared by vacuum arc-melting,in this paper the aluminothermic reaction has been used to prepare CoCrFeMnNi ?MoCrFeMnNi?TiCrFeMnNi high-entropy alloy.The phase composition?morphology and mechanical properties of the three kinds high-entropy alloy were studied and the change of sructure and performance after 700 ?? 800 ??1000 ? annealing also have been studied.MoCrFeMnNi high-entropy alloy prepared by aluminothermic reaction is the typical dendrite structure.The dendrite is body-centered cubic phase with Mo and Cr enrichment and the interdendrite is face-centered cubic phase with Ni enrichment.With the increase of annealing temperature,the dendrite phase became thicker and the interdendrite became smaller.The interdendrite would precipitate nano-sized precipitated phase after annealing and the precipitated phase was grow up with the increase of annealing temperature.The plasticity of alloy is very poor and the compression strength of alloy did not improve significantly after annealing.Due to the effect of solid solution strengthening of the Mo atoms,the hardness of MoCrFeMnNi high-entropy alloy is very excellent.The hardness was improved after annealing because of the precipitation strengthening effect and the hardness of alloy reached the maximum 667 HV after 800? annealing.CoCrFeMnNi high-entropy alloy prepared by aluminothermic reaction is mainly face-centered cubic structure.The as-cast alloy had brittleness precipitated phase and the brittleness precipitated phase was dissolved after annealing.Due to the brittleness of the precipitated phase,the strength and plasticity of the as-cast alloy was reduced.The strength and plasticity was improved after annealing.The tensile strength reached 477 MPa and the elongation reached 49% after 800 ? annealing.The dimple of CoCrFeMnNi of high-entropy alloy fracture morphology is dense after annealing and the dimple socket exists ball-like precipitated phase.The hardness of CoCrFeMnNi high-entropy alloy is lower than the other two kinds of alloys and the hardness maximum is 144 HV.TiCrFeMnNi high-entropy alloy prepared by aluminothermic reaction is dentrite structure.The dendrite rich in Ti?Ni element and the interdendrite rich in Cr?Fe element.The strip-like precipitation is distributed in the interdendrite of as-cast alloy.With the increase of annealing temperature the precipitation phase has been dissolved and the precipitated phase was dissolved completely after 1000 ? annealing.The phase composition of TiCrFeMnNi high-entropy alloy is complicated and it is consist of mainly face-centered cubic phase and a little amount of face-centered cubic phase?? phase and laves phase.The hardness of TiCrFeMnNi high-entropy alloy is very high and the hardness reached 810 HV after 700 ? annealing.