Zr-sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为(1010)方向平行于轧向((1010)∥RD),而退火后转变为(1210)方向平行于轧向((1210)∥RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C∥ND)的取向;最终退火板材的大晶粒多为(1210)∥RD的基面织构,小晶粒则以(1010)∥RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.

HETEROGENEOUS MICROSTRUCTURE AND TEXTURE EVOLUTION DURING FABRICATION OF Zr-Sn-Nb ZIRCONIUM ALLOY SHEETS

Zirconium alloys are widely used as fuel cladding and structural materials for nuclear reactors due to the low neutron absorption cross-section,good corrosion resistance and acceptable mechanical properties.These properties are greatly dependent on microstructural and textural features, such as grain morphology,grain size,crystallographic texture and distribution of precipitates.It is necessary to understand microstructure and texture evolution during fabrication in order to optimize the manufacturing process and to improve the service performance.In this work,microstructure and texture evolution during fabrication of Zr-Sn-Nb new zirconium alloy sheets are investigated using XRD,SEM-ECC,TEM and EBSD.The results show that the random texture formed byβquenching transforms into tilt basal texture after hot rolling.The basal texture keeps stable during the following fabrication stages.The texture of the rolling sheets is mainly characterized as〈1010〉direction parallel to rolling direction(〈1010〉∥RD),while the texture of the annealing sheets is〈1210〉direction parallel to rolling direction(〈1210〉∥RD).The microstructure evolves from a weave Widmansatten structure ofβquenching stage to heterogeneous deformation structures associated with hot and cold rolling and then to a fully recrystallized structure after final annealing.The cold rolling sheets present more heterogeneous structures in which the C axes of less deformed grains mostly concentrate in the normal direction.The larger grains in annealed structures mostly belong to the〈1210〉∥RD basal texture while the smaller grains are in the〈1010〉∥RD orientation.The reason for the heterogeneous deformation structures and texture evolution during annealing are discussed according to the deformation and recrystallization mechanisms.