Study On The Composition And Mechanical Processing Influence On Microstructure And Texture In Zirconium Alloys

Zirconium alloy was chosen for use in the core of water-cooled nuclear reactors because of its low thermal neutron capture cross-section,reasonable mechanical properties and adequate corrosion resistance in high temperature water. Moreover, the microstructure of zirconium alloy, especially the precipitates, such as the size, distribution, and kind of that, have a profound influence on both anti-corrosion and mechanical ability. in addition , there is a formation of texture during the Zirconium mechanical processing which have an effect on the Hydrideorientation,mechanical properties,irradiation growth and the anti-corrosion properties. composition and mechanical processing play a very important role in the formation of the microstructure and texture.it is necessery to master the microstructure and texture evolution changed with composition and the mechanical processing .so can we optimize the properties of the Zirconium.in order to know this ,In this paper,the evolution of microstructure and texture during the change of composition and the mechanical processing was investigated with Electron channeling contrast (ECC), electron backscatter diffraction (EBSD),X-ray diffraction, and scanning transmission electron microscopy (TEM).The investigation of microstructure and texture in Zr-Nb and Zr-Sn-Nb showed that(1) the grain of annealing materials is uniform and equiaxed , and most of the grain size ranges from 2 to 5μm,the second phase particles(SPP) is very different between the two kind of alloys. the main texture of final annealing is the basal texture ,and the maximum is spread out towards the transverse direction. And the <-12-10> directions align parallel to the rolling direction.the result showed that composition play a little influnce on the texture and the microstructure.(2)there are a big different between the two kind of alloys . the SPP dispersed evenly in Zr-Sn-Nb with the size between 50¹00nm,we find two kind of precipitates by means of TEM ,the first one is Zr(NbFeCr)₂ with a HCP structure ,the other one is proved to be the (ZrNbCr)₂Fe with the FCC structure; there are two kind of precipitates in the Zr-Nb-Cu alloy. The first one isβ-Nb with a BCC structure,small size (50¹50nm)and a distribution in the grain ,the other one is Zr₂Cu precipitates with a tetragonal structure, big size(200⁵00nm) and distributed on the grain boundary.The investigation of microstructure and texture during the mechanical processing in the T6 Zirconium alloy showed that:(1) T6 Zirconium alloy obtain a lath martensite microstructure after quebch,due to big deformation during the hot rolling,the original structure was elonged there are also some recrystalled grain exist, we final obtain uniform and equiaxed recrystalled grain with the grain size between 3⁵um after twice of cold rolling and annealing.(2) there is a change from random texture to a the basal texture after hot rolling ,and the maximum is spread out towards the transverse direction. It keeped the texture type duing the followed mechainal processing ,but there are a highter intensity in rolling sheet than annealing sheet.and in the rolling sheet with the {0001}<10-10> texture as a main texture ,but a {0001}<11-20> in the annealing sheet. (3)The alloy element completely dissolve in the matrix after quench,and separate out from matrix as precipitates during hot rolling, the precipitates show a belt type distribution along the RD direction, the precipitates grow after hot rolling and the belt structure disappear,in the follow fabrications, the particles is more evenly distributed after the annealing processes than cold rolling.