Storogilov G. The microstructure formation and properties of the alloy HT-50 change, under deformation and thermal influences

The dissertation is devoted to establishing the regularity of structure of superconducting Nb-Ti alloys formation under the influence of various factors intensive plastic deformation, diffusion decomposition and determining the relationship between the parameters of influences, of the structure characteristics and physico-mechanical properties. First applied to Nb-Ti alloys, the multi-cycle method «upsetting-extrusion» led to implementing them in a finely dispersed and homogeneous sub-microcrystalline structure. The formation of such structures contributes to the effective decomposition of the metastable solid solution. The process of separation α-Ti-phase is accelerated and its volume fraction increases. This improves the Jc of superconductors made by technology using this method. Holding the MUE also provides increased strength and ductility of Nb-Ti alloys. The improvement in the mechanical characteristics breakage of fibres were reduced, and the elongated of superconductor increases. The regularities of interrelation of parameters of mechanical-thermal influence (degree of pre-strain, temperature and time of intermediate and final heat treatments, the number of heat treatments, the degree of deformation between the heat treatments and the degree of final deformation) with characteristics of the separation in α-Ti-phase, and level of Jc in Nb-Ti superconductors. It is shown that to achieve high current-carrying ability of the volume fraction of α-Ti-phase should be as large, and its optimal size to provide the final degree of deformation. Made of long multi-strand Nb-Ti superconductors of different designs with high current-carrying capacity (up to ~ 3,6*105 A/cm2 at B=5 T). The obtained conductors were handed over to the customer for the manufacture of the magnetic system high-gradient cryomagnetic separator. Using the developed optimal regimes obtained Nb-Ti superconductor with the record current-carrying capacity (4*105 A/cm2, B=5 T).