| Materials challenges must be successfully resolved for nuclear energy to continue to make further improvements in reliability,safety and economics.Compared to traditional ultra-low carbon stainless steels,titanium alloys with high specific strength,good process performance,excellent impact resistance,low radioactivity and low radiation swelling tendency,have proved their great potential in spent nuclear fuel reprocessing,power reactor miniaturization,modular mobile nuclear reactor and spent nuclear fuel storage tanks applications.Especially since the 1980s,with the development of of low-radioactive materials,Russia,Japan and other western countries have started the application and research of titanium alloys in the field of nuclear power.In this research,a medium-strength,high-toughness,radiation-resistant,low-radioactive Ti-5Al-3V-3Zr-0.7Cr（Ti-5331,wt%）alloy was developed based on[Al]eq and[Mo]eqcalculations,crystal structure design techniques,neutron irradiation tests and alloying element optimization.Both laboratory and industrial Ti-5331 alloy ingots were prepared,and the relationship among its microstructure,processing and properties were systematically investigated.Additionally,the microstructure and texture evolution in the Ti-5331 alloy sheet with different processing parameters were studied and discussed.The influence of irradiation dose and temperature on the material performance was also deeply investigated.The main research conclusions are as follows.（1）[Al]eq and[Mo]eq calculations and crystal structure design methods were applied to optimize the alloy composition（Ti-Al-V-Zr-Cr）,to meet the low radiation resistance and low radiation activity.The radiation-induced decay cycle of the new alloy is close to that of pure titanium,and it can meet the requirements of recycling within 4 years.（2）It was found that with the increase of Cr content,the grains of Ti-Al-V-Zr alloy can be significantly refined without reducing plasticity.In addition,the Cr content also significantly affects the neutron shielding properties.Alloy with 0.76wt%Cr showed the best comprehensive properties.（3）Isothermal thermal compression tests were carried out to study the high temperature deformation behavior of the Ti-5331 alloy.The constitutive model of the alloy was established based on hyperbolic sine equation,which revealed the relationship between critical strain of dynamic recrystallization and the peak strain,as well as the recrystallization fraction behaviors.Based on the dynamic material model,the high-temperature deformation stability zone of the alloy was established:850～900℃/0.01～0.1s-1.（4）The effect of rolling temperature,deformation reduction and heat treatment on the performance,microstructure and texture of the Ti-5331 titanium alloy sheet was studied.While the rolling temperature was below theβphase transformation temperature,{0001}∥ND and{1010}∥RD texture was obtained;When the rolling temperature was above theα+β/βphase transformation temperature,no obvious texture in the sheet was formed.After900℃/1h,AC heat treatment,the alloy showed the best comprehensive mechanical properties:Rm=920MPa,A=18%,V-notch impact toughness is 93J/cm2.（5）The effect of He+irradiation temperature and irradiation dose on the microstructure and mechanical properties of Ti-5331 alloy were studied.Under small irradiation doses,the surface morphology of the alloy was intact but contained spherical bulges.Under high irradiation doses,particle precipitates appeared on the surface of the alloy.At low irradiation temperatures,precipitated particles also appeared on the surface of the alloy,and at high irradiation temperatures,tcrackings started to appear.The microstructure of the alloy without any precipitation was observed without irradiation. |
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