Study On High-entropy Alloy AlCrCuFe(Mo_x,Nb_x) For Nuclear Fuel Cladding

Nuclear fuel cladding tubes are an important part of nuclear reactors,but the widely used Zr alloy fuel cladding tubes have defects in accident tolerance.The concept of high-entropy alloy has become one of the hotspots of material research since its introduction.The alloy breaks through the concept of traditional alloy design,and produces high entropy effect by multi-primary element mixing,which makes its structure simple and does not form complex phase structure.The high-entropy alloy has the following advantages:?1?the phase structure is simple;?2?has many excellent properties not possessed by conventional alloys,such as high hardness,good corrosion resistance,stable thermal stability,and excellent irradiation performance,etc.Therefore,high-entropy alloys have great application prospects in the field of nuclear fuel cladding tubes.According to the performance requirements of nuclear fuel cladding tubes and the formation conditions of high-entropy alloys,the main elements of high-entropy alloys were selected.Two high-entropy alloy systems were prepared by theoretical calculation and arc melting technology,respectively are AlCrCuFeMo_x and AlCrCuFeNb_x?x=0,0.3,0.5,0.7,1.0?.The relationship between the microstructure,phase structure and properties of the alloy and the content of Mo and Nb elements was analyzed,and the high pressure pure water corrosion and high temperature steam oxidation performance tests were carried out under the conditions of nuclear fuel cladding.Mainly get the following results:?1?The phase structure of AlCrCuFeMo_x high-entropy alloy changes with the addition of Mo element,and the original FCC+BCC phase structure transforms into double BCC phase structure;The hardness and strength of the alloy increase with the increase of Mo content.However,the plasticity is poor.The hardness and strength of AlCrCuFeMo alloy are the highest,596.6 HV and 1902.27 MPa respectively.The wear resistance is better than that of Zr alloy nuclear fuel cladding and AlCrCuFeNb high entropy alloy.The oxidation resistance of 1200°C in water vapor environment is better than that of Zr alloy.When Mo content is 1.0,the alloy has the best resistance to high temperature steam oxidation.The oxidation weight gain of 1h is 59.5 mg/dm²,which is much smaller than Zr alloy?3932 mg/dm²?,and the oxidation product after oxidation is Al2O3.However,the series of high-entropy alloys have been corroded in high-pressure pure water corrosion experiments,and the corrosion products are easy to fall off,so satisfactory results cannot be obtained.?2?The phase structure of AlCrCuFeNbx high-entropy alloy changes with the addition of Nb element,and the original FCC+BCC phase structure changes to FCC+BCC+Cu₉Al₄phase structure;The hardness and strength of this series of alloys increase with the content of Nb.The hardness and strength of the alloys increase with the increase of Nb content,but the plasticity is poor.The hardness and strength of AlCrCuFeNb alloy are the highest,756 HV and 1865.95 MPa respectively;Its wear resistance is better than Zr alloy nuclear fuel cladding;The oxidation resistance in 1200°C water vapor environment is superior to Zr alloy,and the high temperature oxidation resistance of AlCrCuFeNb high-entropy alloy is the best.The oxidation weight gain of 1h is 36.8 mg/dm²,which is much smaller than that of Zr alloy,which is 3932 mg/dm²,and the alloy is not deformed and oxidized.The layer is denser and is superior to the high temperature oxidation resistance of AlCrCuFeMo high-entropy alloy in terms of oxidation weight gain.The resulting oxidation product is mainly Al₂O₃,in addition to a small amount of CrNbO₄ oxide.However,corrosion occurred in the high-pressure pure water corrosion test,and the corrosion products were detached.The corrosion weight gain of the AlCrCuFeNb high-entropy alloy was not large,so there is a possibility to continue to improve the performance.The addition of Mo element and Nb element effectively improves the hardness,strength and wear resistance of the high-entropy alloy.In particular,the oxidation resistance of high temperature water vapor has been greatly improved.Among them,AlCrCuFeNb high-entropy alloy has lower high-temperature steam oxidation weight gain and lower pure water corrosion weight gain,which is far superior to Zr alloy nuclear fuel cladding tube in the field of accidental fault tolerance performance.It has great application prospects in the field of nuclear fuel cladding tubes.However,the data of the alloy in the high-pressure pure water corrosion test still can not meet the nuclear reactor work requirements,and further improvement and testing are needed.