Study On Microstructure,Texture And Second Phase Of New Zirconium Alloy Tube

With the improvement of nuclear reactor burnup and refueling cycle prolong,traditional zirconium alloys gradually do not meet the need.It is imperative to develop new zirconium alloys with better corrosion resistance and mechanical properties.The ways of development new zirconium alloy are mainly to adjust the composition or optimize the processing.There two ways will make organization change a lot.Characterizing the microstructure of new zirconium will effectively promote the development of new zirconium.It can provide sufficient experimental data and theoretical support for optimizing the processing and improving the performance of zirconium alloy,which can provide some reference for further research.It also can provide some reference for follow-up study.The thesis studied three kinds of zirconium alloys which were Zr-Nb-Fe-Cu series alloy with stress relief annealing state(A),Zr-Nb-Fe-Cu series alloy with recrystallization annealing state(B)and Zr-Nb-Fe series alloy with recrystallization annealing state(C).Using optical microscope(OM)and electron channel contrast imaging(ECC)quantitatively characterized microstructure of samples.Using electron backscatter diffraction(EBSD)and X ray diffraction(XRD)analyzed the sample crystal orientation and texture type.Using transmission electron microscopy(TEM)and Secondary electron imaging(SE)characterized second phase particles.Some conclusions were obtained below:The microstructure of sample A was mainly composed of elongated fibrous deformed grains.In addition,there were a little of hard deformed grains and fine recrystallized grains.The microstructure of sample B which was recrystallization annealing state was mainly near equiaxed recrystallized grains but there were still a lot of elongated grains.Recrystallization is not sufficient and the average grain size is 4.75 ?m.The sample C was recrystallized and the microstructure was similar to equiaxed grains.However,the structure was more uniform than sample B.The recrystallization of sample C was more sufficient and the average grain size was 4.88 ?m.(2)The three samples all had typical bimodal texture.The sample A had typical <101(?)0///RD fiber texture.The sample B had annealed fiber texture <112(?)0///RD and some <101(?)0///RD texture.Samples C only had annealed fiber texture <112(?)0///RD.The texture intensity of stress relief annealing sample was significantly stronger than the recrystallized samples.The texture orientation factor of three sample was calculated.The results show that the fND of the recrystallized samples is higher than stress relief annealing sample and the recrystallization was more sufficient the value of fND was greater.(3)The shape of second phase particles(SPPs)in sample A was sphere,ellipsoid or clavate.Those particles were along fibrous tissue with zonal distribution.The SPPs distribution in the sample B was more diffuse but there were still some particles at the grain boundary distribution,forming the second phase cluster structure.The morphology of SPPs were mainly spherical with a few number of short rod.The distribution of sample C was more random.The morphology was spherical and a little of irregular short rod.The SPPs of sample B were small and had a large quantity.The average diameter of sample B was 51.89 nm.The number of SPPs of sample C was small but the size was 96.45 nm bigger than sample B.The sample A was between the two,the average diameter of the second phase was 54.32 nm.Sample A,B the size of the second phase was mainly focused on 20 nm to 60 nm.The proportion accounted for about 75%.The second phase size distribution of sample C was more uniform and the distribution range was wider.The SPPs of the three samples all contained Zr(Nb,Fe,Cr)2 phase and ?-Nb phase.The Zr(Nb,Fe,Cr)2 phase in the samples B and C had obvious stacking fault structure.