Effect Of Pre-compressed Deformation On Precipitation Behavior Of Zr-Sn-Nb Alloy During Aging

In this study,multiple characterization and analysis techniques including scanning electron microscope（SEM）,electron channel contrast（ECC）,electron backscatter diffraction（EBSD）and transmission electron microscope（TEM）are used in the investigation of Zr-0.85Sn-0.4Nb-0.4Fe-0.1Cr-0.05Cu alloy.This paper systemically studied the recrystallization behavior,recrystallization grain size,morphologies and distribution evolution,growth kinetics and precipitation evolution of second phase particles（SPPs）during aging after quenching.Meanwhile,the effect of 6%and 12%pre-compression deformation on the above issue is also the key research content in present paper.Main conclusions attained in present are as follows:（1）The microstructure of the Zr-Sn-Nb alloy aged at 550-700℃for 30-1800 min can be generally separated into two groups by their morphologies.One type is plate structure obtained when the alloy were on the early stage of aging;the other one is recrystallization structure transformed from plate structure with the increase of aging temperature and prolongation of holding time.The plate structures recrystallized by strain induced grain boundary migration（SIBM）mechanism in specimens without pre-deformation,and recrystallization structure remained orientation feature of priorαplates.（2）Second phase particles’precipitation is closely related to the recrystallization process.The linear distribution of SPPs gradually transforms into randomized with the process of recrystallization.When the SPPs fully precipitate,the growth of SPPs in Zr-Sn-Nb alloy using in this paper during aging after quenching follows to Kahlweit’s second order growth kinetics.The growth activation energy in alloy without pre-deformation is experimentally determined to be 214 kJ/mol.From TEM observation,There are two types of SPPs in the alloys after aging at 550-700℃for 30-1800 min,including orthorhombic Zr₃Fe containing Cu element and hexagonal Zr（Fe,Cr,Nb）₂（C14-Laves）,and the sizes of Zr₃Fe are bigger than Zr（Fe,Cr,Nb）₂.（3）The introduction of pre-deformation can accelerate the recrystallization process,and make recrystallization can carry at a lower temperature and using shorter holding time.Deformation could also refine recrystallized grains,and 12%pre-deformation is more significant than 6%on refinement effect.Unlike alloys without pre-deformation,specimens pre-formed by 6%and 12%recrystallized through the subgrain growth nucleation.There is no similarity between recrystallization grains and the plate structure in orientation characteristics.The originalβgrain boundary is showing signs of gradual disappearance.And pre-deformation could promote the uniform distribution of SPPs.In addition,pre-deformation is in favor of refining SPPs.The average size of the second phase particles in 12%pre-deformation alloy is the smallest after the same aging treatment.Pre-deformation can also slightly reduce the growth activation energy of SPPs.According to the results of experiment,the value decreased to 203 kJ/mol after 6%pre-deformation,and it reduced to 202 kJ/mol after 12%pre-deformation.The pre-deformation has no remarkable impact on the type of SPPs.