Effect Of Annealing And Pre-deformation On Microstructure And Properties Of A Novel Zirconium Alloy

Zirconium alloys are widely used as the cladding and structural materials of nuclear reactors due to its good corrosion resistance,low thermal neutron capture cross section and high strength.Rolling and heat treatment processes are involved in the processing of zirconium alloy strip,its final status affect many properties of it and the safety of nuclear reactors.It is of great significance to explore the process of the novel zirconium alloy,so a series of studies on the microstructure and mechanical properties of a zirconium alloy strip after annealing and deformation were carried out.The results of the study are expected to provides a useful reference for the localization of novel zirconium alloy for nuclear reactors.In this paper,metallographic microscope,scanning electron microscopy,electron backscatter diffraction,X-ray diffraction,transmission electron microscopy,universal testing machine were used to research a novel zirconium alloy strip,first the microstructure and mechanical properties of novel zirconium alloy strips and under different annealing processes were studied,the main conclusions are as follows:The grains are eauiaxed whose average grain size after annealing at 560?620?×3h are distribution between 2.3?2.8 ?m.The average size of second phase particle are between 70?80nm,which are body-centered cubic ?-Nb phase and hexagonal close packed Zr-Nb-Fe phase.Annealing near the allotropic transformation temperature the size of second phase particles is significantly increased and distribute concentrated on the grain boundary.The grain's<0001>is in the ND-TD plane and tilts toward TD and there were<10 10>//RD and<11 20>//RD texture.As the annealing temperature increases the strength of basal texture decreases and then rises,strength obtained at 580?×3 h is at least being 6.14;The texture of<1120>//RD showed a tendency to increase slowly.The change of texture is not obvious when extending holding time.Annealing at 560?620?×3h both ?s and ?b in the RD and TD are reduced compared to the original material,the texture parallel to RD is the main reason that affects the difference in mechanical properties in three directions;Annealing near the allotropic transformation temperature a large amount of the second phase accumulates at the grain boundary,causing brittle fracture.Second the microstructure and mechanical properties of novel zirconium alloy strips after pre-deformation and annealed were studied.The main conclusions are as follows:pre-deformation from 2%-10%,the grain has't changed much;Pre-deformation of 14%produces a significant increase of distorted grains.The average grain size of 2%pre-deformation+annealing at 580?×3h is 2.5?m,and the average grain size of other pre-deformation+annealing are refined.Pre-deformation processes produce dislocation networks inside the grain,when annealed at 580?×3h it will form subgrains and arrays with low dislocation density;The textures of 2%,6%,and 10%pre-deformation are still basal bimodal textures.The<1010>//RD texture gradually increased with the deformation increased from 2%to 10%,when reach 14%<1120>//RD texture disappears.Extending annealing time at 580?,some strong<1010>//RD texture generated by 6%pre-deformation transform into<1120>//RD texture;The Schmid factor of the {1010}<1210>and {1011}<1210>slip system are larger than the basal slip system,prismatic and pyramidal slips are are easier to start;The ?s after pre-deformation+annealing is decreases while ?b is increases;After 6%pre-deformation+580? ×3h annealing the ?b is a maximum value of 550.3 MPa.