Heat treatment significantly influences homogeneous material microstructures and mechanical properties,which can be improved by an optimal heat treatment process.However,heat treatment application to heterogeneous mat...Heat treatment significantly influences homogeneous material microstructures and mechanical properties,which can be improved by an optimal heat treatment process.However,heat treatment application to heterogeneous materials presents significant challenges due to compositional and microstructural heterogeneities.Herein,a laminated heterostructured alloy comprising alternating316L stainless steel(SS)and 18Ni300 maraging steel(MS)layers fabricated using wire and arc additive manufacturing was investigated.A solution treatment was applied at900℃for 0.5 h.Subsequently,the solution-treated and asfabricated(AF)samples were aged at 500℃for 4 h;these samples were denoted SA and AT,respectively.The AT phase compositions and orientations were similar to those of AF.The SA 316L SS layer resembled that of AF,but the SA 18Ni300 MS layers exhibited a reduced austenite phase fraction and refined grain size,attributable to solid-state transformation.In the AT sample,aging induced the formation of nanoscale acicularωphase and ellipsoidal Ni_(3)Ti,Fe_(2)Mo,and X precipitates in the 18Ni300 MS layers.Conversely,the SA precipitates contained acicular Fe Ni_(2)and ellipsoidalω,Ni_(3)Ti,and X precipitates,and their fractions were lower than those in AT precipitates.The18Ni300 MS layer microhardness in the heat-treated samples increased due to nanoprecipitation,but the 316L SS layer microhardness resembled that of AF.The AT and SA ultimate tensile strengths increased to(1360±50)and(1473±41)MPa,respectively,attributable to precipitation strengthening.The SA 316L SS layer exhibited a high stress-induced martensite fraction,enhancing the ductility of heated samples.展开更多
Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.Methods The electricfield distribution,bias voltage range and electron beam...Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.Methods The electricfield distribution,bias voltage range and electron beam quality under different cathode positions were simulated by CST software.Results Changes in the cathode position can cause changes in the electricfield distributions under the cathode emission surface change,thereby changing the size of the effective emitting area and affecting the relationship between the bias voltage and beam current.Conclusions Only when the cathode is installed in the proper positions,the beam current and the bias voltage have an approximately linear proportional relationship.When the cathode is installed improperly,the electron beam emission is disordered,resulting in decreased electron beam quality.展开更多
基金supported by the National Natural Science Foundation of China(No.52301050)the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(No.2022QNRC001the China Postdoctoral Science Foundation(No.2023M741701)。
文摘Heat treatment significantly influences homogeneous material microstructures and mechanical properties,which can be improved by an optimal heat treatment process.However,heat treatment application to heterogeneous materials presents significant challenges due to compositional and microstructural heterogeneities.Herein,a laminated heterostructured alloy comprising alternating316L stainless steel(SS)and 18Ni300 maraging steel(MS)layers fabricated using wire and arc additive manufacturing was investigated.A solution treatment was applied at900℃for 0.5 h.Subsequently,the solution-treated and asfabricated(AF)samples were aged at 500℃for 4 h;these samples were denoted SA and AT,respectively.The AT phase compositions and orientations were similar to those of AF.The SA 316L SS layer resembled that of AF,but the SA 18Ni300 MS layers exhibited a reduced austenite phase fraction and refined grain size,attributable to solid-state transformation.In the AT sample,aging induced the formation of nanoscale acicularωphase and ellipsoidal Ni_(3)Ti,Fe_(2)Mo,and X precipitates in the 18Ni300 MS layers.Conversely,the SA precipitates contained acicular Fe Ni_(2)and ellipsoidalω,Ni_(3)Ti,and X precipitates,and their fractions were lower than those in AT precipitates.The18Ni300 MS layer microhardness in the heat-treated samples increased due to nanoprecipitation,but the 316L SS layer microhardness resembled that of AF.The AT and SA ultimate tensile strengths increased to(1360±50)and(1473±41)MPa,respectively,attributable to precipitation strengthening.The SA 316L SS layer exhibited a high stress-induced martensite fraction,enhancing the ductility of heated samples.
基金funded by National Natural Science Foundation of China(Nos.51805265,51775527)Natural Science Foundation of Jiangsu Province(No.BK20180472).
文摘Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.Methods The electricfield distribution,bias voltage range and electron beam quality under different cathode positions were simulated by CST software.Results Changes in the cathode position can cause changes in the electricfield distributions under the cathode emission surface change,thereby changing the size of the effective emitting area and affecting the relationship between the bias voltage and beam current.Conclusions Only when the cathode is installed in the proper positions,the beam current and the bias voltage have an approximately linear proportional relationship.When the cathode is installed improperly,the electron beam emission is disordered,resulting in decreased electron beam quality.
