中国低活化马氏体钢在液态Pb-Bi中的脆化现象
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摘要
为了评价反应堆候选结构材料与液态金属的相容性,针对低活化马氏体钢在液态Pb-Bi共晶中的拉伸脆化现象,采用2种拉伸速率的拉伸实验,研究了中国低活化马氏体钢(CLAM)在200~500℃范围内的Ar气和液态Pb-Bi共晶环境中的拉伸断裂行为。结果表明,在Ar气环境中拉伸时,CLAM钢均为韧性断裂;而在液态Pb-Bi共晶环境中拉伸时,在300~450℃下会出现脆性断裂现象。在300~450℃脆化温度区间内试样强度变化不大,但总延伸率显著降低,出现"韧谷"现象。然而拉伸温度在低于或高于脆化温度区间时,脆断现象消失,总延伸率回复到与对比试样相同水平。在更低的拉伸速率下,CLAM钢发生"韧谷"现象的温度区间明显扩大,表明拉伸速率对CLAM钢在液态Pb-Bi共晶中的脆化也有影响。经低温回火硬化后,CLAM钢在液态PbBi共晶中出现拉伸脆化现象是由于液态Pb-Bi接触裂纹尖端后造成表面能降低,进而降低临界解理应力而发生脆性断裂。
China low activation martensitic(CLAM) steel has been considered as the primary candidate structural material for application in fusion systems because of its good thermal conductivity and low thermal expansion ratio. In this work, the tensile behavior of the CLAM steel in liquid lead-bismuth eutectic was investigated to assess the compatibility of CLAM steel with liquid metal. The CLAM steel was tempered before test. The tensile tests were performed in liquid lead-bismuth eutectic and argon gas respectively at different temperatures ranging from 200 ℃ to 500 ℃ under different strain rates. All the specimens ruptured in ductile manner in argon gas environment, exhibiting obvious necking and dimples on the fracture surface. For those tested in liquid lead-bismuth eutectic, the specimens behaved ductile fracture when the test temperature was below 250 ℃, but fractured in brittle cleavage manner in the temperature range of 300~450 ℃. The embrittlement mainly occurred after necking, showing typical river pattern on the fracture surface with slight necking trace,and obvious cracking points were observed to initiate at the fracture edge and propagated towards the center of the specimen,namely,the appearance of the ductility trough that shows significant degradation in total elongation while no noticeable differences in strength compared with the tested specimens in argon gas environment.Furthermore,the brittle fracture disappeared and total elongation recovered when the tensile tests were performed out of the embrittlement temperature range.In slower strain rate tensile(SSRT)tests,the temperature range of the ductility trough greatly expanded and brittle fracture occurred at temperatures below 250℃.The results indicate that CLAM steel is susceptible to embrittlement in liquid lead-bismuth eutectic.This is because the contact of the liquid metal with the cracking tip leads to a decrease of the interfacial energy,which further reduces the critical cleavage stress and facilitates the brittle fracture.Both temperature and strain rate are evidenced in this work to have an effect on the embrittlement of CLAM steel.
China low activation martensitic(CLAM) steel has been considered as the primary candidate structural material for application in fusion systems because of its good thermal conductivity and low thermal expansion ratio. In this work, the tensile behavior of the CLAM steel in liquid lead-bismuth eutectic was investigated to assess the compatibility of CLAM steel with liquid metal. The CLAM steel was tempered before test. The tensile tests were performed in liquid lead-bismuth eutectic and argon gas respectively at different temperatures ranging from 200 ℃ to 500 ℃ under different strain rates. All the specimens ruptured in ductile manner in argon gas environment, exhibiting obvious necking and dimples on the fracture surface. For those tested in liquid lead-bismuth eutectic, the specimens behaved ductile fracture when the test temperature was below 250 ℃, but fractured in brittle cleavage manner in the temperature range of 300~450 ℃. The embrittlement mainly occurred after necking, showing typical river pattern on the fracture surface with slight necking trace,and obvious cracking points were observed to initiate at the fracture edge and propagated towards the center of the specimen,namely,the appearance of the ductility trough that shows significant degradation in total elongation while no noticeable differences in strength compared with the tested specimens in argon gas environment.Furthermore,the brittle fracture disappeared and total elongation recovered when the tensile tests were performed out of the embrittlement temperature range.In slower strain rate tensile(SSRT)tests,the temperature range of the ductility trough greatly expanded and brittle fracture occurred at temperatures below 250℃.The results indicate that CLAM steel is susceptible to embrittlement in liquid lead-bismuth eutectic.This is because the contact of the liquid metal with the cracking tip leads to a decrease of the interfacial energy,which further reduces the critical cleavage stress and facilitates the brittle fracture.Both temperature and strain rate are evidenced in this work to have an effect on the embrittlement of CLAM steel.
引文
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[14]Legris A,Nicaise G,Vogt J B,et al.Embrittlement of a martensitic steel by liquid lead[J].Scr.Mater.,2000,43:997
[15]Nicaise G,Legris A,Vogt J B,et al.Embrittlement of the martensitic steel 91 tested in liquid lead[J].J.Nucl.Mater.,2001,296:256
[16]Dai Y,Long B,Jia X,et al.Tensile tests and TEM investigations on Li So R-2 to-4[J].J.Nucl.Mater.,2006,356:256
[17]Dai Y,Wagner W.Materials researches at the Paul Scherrer Institute for developing high power spallation targets[J].J.Nucl.Mater.,2009,389:288
[18]Van den Bosch J,Coen G,Bosch R W,et al.TWIN ASTIR:First tensile results of T91 and 316L steel after neutron irradiation in contact with liquid lead-bismuth eutectic[J].J.Nucl.Mater.,2010,398:68
[19]Long B,Dai Y,Baluc N.Investigation of liquid LBE embrittlement effects on irradiated ferritic/martensitic steels by slow-strainrate tensile tests[J].J.Nucl.Mater.,2012,431:85
[20]Joseph B,Picat M,Barbier F.Liquid metal embrittlement:A stateof-the-art appraisal[J].Eur.Phys.J.Appl.Phys.,1999,5:19
[21]Shchukin E D.Physical-chemical mechanics in the studies of Peter A.Rehbinder and his school[J].Colloids.Surf.,1999,149A:529
[22]Stoloff N S,Johnston T L.Crack propagation in a liquid metal environment[J].Acta Metall.,1963,11:251
[23]Ye C Q,Vogt J B,Serre I P.Liquid metal embrittlement of the T91steel in lead bismuth eutectic:The role of loading rate and of the oxygen content in the liquid metal[J].Mater.Sci.Eng.,2014,A608:242
[24]Hémery S,Auger T,Courouau J L,et al.Effect of oxygen on liquid sodium embrittlement of T91 martensitic steel[J].Corros.Sci.,2013,76:441
[25]Mart????n F J,Soler L,Hernández F,et al.Oxide layer stability in lead-bismuth at high temperature[J].J.Nucl.Mater.,2004,335:194
[2]Kurtz R J,Alamo A,Lucon E,et al.Recent progress toward development of reduced activation ferritic/martensitic steels for fusion structural applications[J].J.Nucl.Mater.,2009,386-388:411
[3]Muroga T,Gasparotto M,Zinkle S J.Overview of materials research for fusion reactors[J].Fusion.Eng.Des.,2002,61-62:13
[4]Jones R H,Heinisch H L,Mc Carthy K A.Low activation materials[J].J.Nucl.Mater.,1999,271-272:518
[5]Chen X Z,Yuan Q B,Madigan B,et al.Long-term corrosion behavior of martensitic steel welds in static molten Pb-17Li alloy at 550℃[J].Corros.Sci.,2015,96:178
[6]Konys J,Krauss W,Voss Z,et al.Corrosion behavior of EUROFER steel in flowing eutectic Pb-17Li alloy[J].J.Nucl.Mater.,2004,329-333:1379
[7]Dai Y,Long B,Groeschel F.Slow strain rate tensile tests on T91 in static lead-bismuth eutectic[J].J.Nucl.Mater.,2006,356:222
[8]Van den Bosch J,Coen G,Hosemann P,et al.On the LME susceptibility of Si enriched steels[J].J.Nucl.Mater.,2012,429:105
[9]Hamouche-Hadjem Z,Auger T,Guillot I,et al.Susceptibility to LME of 316L and T91 steels by LBE:Effect of strain rate[J].J.Nucl.Mater.,2008,376:317
[10]Van den Bosch J,Sapundjiev D,Almazouzi A.Effects of temperature and strain rate on the mechanical properties of T91 material tested in liquid lead bismuth eutectic[J].J.Nucl.Mater.,2006,356:237
[11]Long B,Tong Z,Gr?schel F,et al.Liquid Pb-Bi embrittlement effects on the T91 steel after different heat treatments[J].J.Nucl.Mater.,2008,377:219
[12]Liu J,Huang Q Y,Jiang Z Z,et al.Effect of strain rate on the mechanical properties of CLAM steel in liquid Pb Li eutectic[J].Fusion.Eng.Des.,2013,88:2603
[13]Van den Bosch J,Bosch R W,Sapundjiev D,et al.Liquid metal embrittlement susceptibility of ferritic-martensitic steel in liquid lead alloys[J].J.Nucl.Mater.,2008,376:322
[14]Legris A,Nicaise G,Vogt J B,et al.Embrittlement of a martensitic steel by liquid lead[J].Scr.Mater.,2000,43:997
[15]Nicaise G,Legris A,Vogt J B,et al.Embrittlement of the martensitic steel 91 tested in liquid lead[J].J.Nucl.Mater.,2001,296:256
[16]Dai Y,Long B,Jia X,et al.Tensile tests and TEM investigations on Li So R-2 to-4[J].J.Nucl.Mater.,2006,356:256
[17]Dai Y,Wagner W.Materials researches at the Paul Scherrer Institute for developing high power spallation targets[J].J.Nucl.Mater.,2009,389:288
[18]Van den Bosch J,Coen G,Bosch R W,et al.TWIN ASTIR:First tensile results of T91 and 316L steel after neutron irradiation in contact with liquid lead-bismuth eutectic[J].J.Nucl.Mater.,2010,398:68
[19]Long B,Dai Y,Baluc N.Investigation of liquid LBE embrittlement effects on irradiated ferritic/martensitic steels by slow-strainrate tensile tests[J].J.Nucl.Mater.,2012,431:85
[20]Joseph B,Picat M,Barbier F.Liquid metal embrittlement:A stateof-the-art appraisal[J].Eur.Phys.J.Appl.Phys.,1999,5:19
[21]Shchukin E D.Physical-chemical mechanics in the studies of Peter A.Rehbinder and his school[J].Colloids.Surf.,1999,149A:529
[22]Stoloff N S,Johnston T L.Crack propagation in a liquid metal environment[J].Acta Metall.,1963,11:251
[23]Ye C Q,Vogt J B,Serre I P.Liquid metal embrittlement of the T91steel in lead bismuth eutectic:The role of loading rate and of the oxygen content in the liquid metal[J].Mater.Sci.Eng.,2014,A608:242
[24]Hémery S,Auger T,Courouau J L,et al.Effect of oxygen on liquid sodium embrittlement of T91 martensitic steel[J].Corros.Sci.,2013,76:441
[25]Mart????n F J,Soler L,Hernández F,et al.Oxide layer stability in lead-bismuth at high temperature[J].J.Nucl.Mater.,2004,335:194