Malykhin D. Changes in thin crystalline structure of Hf, Zr and it alloys at different thermal and mechanical treatments

Thesis is devoted to investigations of dynamics of thin crystalline structure (TCS) and it laws in hcp metals (Zr and alloys, Hf) after various kinds of thermo mechanical treatment: cold working, beta-quenching. The task is concerned with problems of distinction of higher technologic and radiation kinds of investigated metals as nuclear materials. By methods of X-ray diffractometry, transmission electron microscopy and metalography it is carried out an analysis of TCS and texture evolution at cold-working of hafnium ГФЭ-1, of zirconium and Zr-1%Nb alloy and also microstructure changing in SHF-quenched materials of Zr-2,5%Nb alloy. Methodological bases of X-ray analysis of strains in hcp metals are developed. Due to it a divided analysis of dislocations structure and intergranular strains are carried out in observed materials. Laws of influence of character of dislocation distribution on texture and microstructure of cold-worked hafnium are established. So, at deformation ~5% there is a stochastic dislocation distribution. It is considered as sings of its conductivity and plasticity of the material. At ~ 15% it is found a formation of dislocations forest and "c+a"-loops. Grows of grains and slowing of texture changing are connected with that. At deformation ~30% it is found a significant structural heterogeneity in the dislocation distribution, which consider as sings of beginning of destruction of material. It is shown that in the pure zirconium and Zr-1%Nb alloy with 90% degree of deformation at 300 and 100 K take place a crystallographic anisotropy of microstructure parameters and constancy of the total characteristic of strains as a combination of both dislocations and intergranular strains. It is established that the cryogenic deformation of the pure zirconium and the alloy promotes to increasing of equivalent resistant pressure on 100…150 MPa. This increment is connected with increasing of dislocations density, with its lower conductivity and with forming in the alloy heterogeneities of the martensitic nature. In result of investigation of TCS state of SHF-quenched samples of Zr-2,5%Nb alloy it is established a nearly isotropic distribution of intergranular strains. Also it is established an effect of microstructure "memory" about of the phase alpfa-beta transformation. It systematically displays as a hcp crystalline structure elastic deformed on ±0,2% up to "rhombic" character.