Study On The Microstructural And Textural Evolution During Annealing Of New Zirconium Alloy Tubes

This thesis reports a quantitative investigation of microstructure and texture evolution during annealing at 560℃, 580℃ and 600℃ of SZA-4 zirconium alloy tubes. Hardness measurements were done to all the samples in order to obtain the hardness curve as function of holding time in different temperature, then the recrystallization volume fraction and kinetics were calculated, and the microstructure and texture evolution were observed and statistic by ECC and EBSD, to investigate the influence of annealing on the microstructure and texture during the recrystallization, thus provide theoretical guidance for industrial production.The micro-hardness results show that as the increasing of holding time, the hardness was decreased gradually, as the increasing of annealing temperature, the hardness change more quickly : annealed at 560℃ for 20 min, the sample hardness significantly decreased and remain unchanged after holding 180 min for HV195; annealed at higher temperature(580℃), the hardness marked drop after holding 10 min and remain unchanged after holding 120 min for HV 195; annealed at 600℃, the hardness droped after holding 5 min and stopped at 60 min for HV 195.The curve of recrystallization volume fraction and time had calculated by equation XV=(HV0-HV)/(HV0-HVrex)show that the time of fully recrystallized is 60 min under 600℃, but annealed at 580℃ and 560℃ need 120 min and 180 min, respectively. So the recrystallization volume fraction increased faster as the higher of annealing temperature. Besides, the activation energy of recrystallization is 163.49KJ/mol according to the JMAK equation.The microstructure of SZA-4 alloy tubes that annealing at different temperature have been quantitatively investigated. It is found that the higher the temperature, the fast recrystallization occurs, namely it waste minimal time when finish recrystallization. Under same time, the longer of the holding time, the more of recrystallization volume percent. The recrytallized grain will grow up when prolong holding time after finish the recrystallization. Besides, according to the Misorientation angle distribution evolution of the SZA-4 cold-rolled tubes annealed at different temperature, the little angel boundary decrease and the high angel boundary increase accompany with process of recrystallization.The pole figures and inverse pole figures of SZA-4 cold-rolled tubes annealed at different temperature have been investigated. The result shows that the pole figures {0001} change little which all distribute on AD-TD and little different in angel bias to pole figure center, it may be case by select region and indexing rate. Mix {101ˉ0}、{112ˉ0} pole figures and inverse pole figures, we can see that the <10 1ˉ0>//AD texture intension change from strong to weak, but <112ˉ0>//AD texture intension change from weak to strong. So, the cold-rolling SZA-4 alloy texture is <101ˉ0>//AD, and the texture turn to <112ˉ0>//AD as recrystallization occur.