Study On Microstructure And Properties Of Al_xCrFeNi_2.5Mo_y High-entropy Alloys

Compared with traditional alloys,high-entropy alloys have many excellent characteristics such as high strength,high corrosion resistance,excellent high-temperature mechanical properties,and good radiation resistance,and are considered to be highly promising structural materials for nuclear energy systems.However,at present,many high-entropy alloy systems contain Co or Cu elements,Co elements are easy to be activated by irradiation,Cu elements are easy to form irradiation brittle precipitates,which deteriorates the mechanical properties of materials,thus posing a great threat to the safety of nuclear energy systems.To this end,this paper proposes to develop a new high-entropy alloy system without Co and Cu elements,designs and prepares two high-entropy alloy systems,Al_xCrFeNi_2.5Mo and Al_xCrFeNi_2.5Mo_1-x,and studies the effect of Al_xCrFeNi_2.5Mo_y high-entropy alloy system on the microstructure,mechanical properties and corrosion resistance of Al_xCrFeNi_2.5Mo_y high-entropy alloy system,and this paper uses X-ray diffraction and scanning electron microscopy Transmission electron microscope,mechanical testing machine and electrochemical workstation and other instruments characterized the structure,mechanical properties and corrosion resistance of alloys,and the following main conclusions were obtained:（1）The change of Al content has a significant effect on the phase composition,microstructure,mechanical properties and corrosion resistance of Al_xCrFeNi_2.5Mo high entropy alloy.With the increase of Al element content,the phase structure of the alloy gradually changed from FCC+σphase to BCC+FCC+σphase,and the microstructure changed from subeutectic structure to dendrite+interdendrite structure+eutectic structure.When compressed at room temperature,Al0 and Al0.2 alloys show good comprehensive mechanical properties.Al0 and Al0.2 alloys also have high tensile strength at room temperature,which are1160MPa and 1015MPa respectively,and the tensile strength of Al0 and Al0.2 alloys at 600℃ can also be maintained to more than 60%of the tensile strength at room temperature.In addition,with the increase of Al element content,the breakdown potential of the alloy decreases,the passive current density increases and the local corrosion resistance decreases.（2）In the Al_xCrFeNi_2.5Mo_1-x alloy system,the synergistic change of Al and Mo elements at the same time has a significant impact on the phase structure,mechanical properties and corrosion resistance of the alloy.With the increase of Al element content and the decrease of Mo element content,the phase structure of alloy changes from FCC+σphase to FCC+BCC phase,and the microstructure gradually changes from hypoeutectic to hypereutectic.Among them,the tensile strength and elongation of Al1.0Mo0 alloy at room temperature were 1090MPa and 16.8%,respectively,which had good comprehensive mechanical properties.The tensile properties of the alloy at 300℃ were similar to those at room temperature,while at600℃,the alloy containing Mo elements could still maintain high strength,but the tensile strength of Al1.0Mo0 alloy without Mo elements was significantly reduced.With the increase of Al/Mo molar ratio,in 3.5wt.%NaCl solution,the ability of alloy to uniform corrosion resistance showed a trend of first strengthening and then weakening.The the addition of Al elements will promote the formation of BCC phase,which is not conducive to the local corrosion resistance of the alloy,in addition,the addition of Mo elements will promote the formation ofσphase,thereby causing Cr element segregation and reducing the local corrosion resistance of the alloy.