Brodnikovskyi D. Influence of second phase particles of Ti-Si and Zr-Cr based alloys on the structure and mechanical properties formation during deformation at higher temperature

For the first time the regularities of formation of deformation structures and mechanisms of dynamic softening in alloys with HCP lattice systems based on Ti-Si and Zr-Cr with different stacking fault energy (SFE) strengthened second phase particles size of 0.5-2 mkm. The presence of particles silicides Ti5Si3 as a result of DR is formed inhomogeneous volume of material of the grain refinement around particles in the alloy Ti-17Al-1,5Zr-1,9Si (at. %). It is look like a coherent framework from small grains. Within a coherent framework of small grains located regions with large grains which can not go to the grain refinement or a movement along the length of significant slots of large-borders. It has been found that the occurrence of stable connected framework with grinded grain causes strain localization in the frame to the certain temperature-strain rate conditions (T = 700 °C , ? = 1,8·10-4 c-1). Localization of deformation occurs due to a decrease in the flow stress of fine-grained material by the action mechanism of slip along the grain boundaries. It is characteristic of structural superplasticity. It is shown that porosity is occurred on the boundary between slots of the material witch deforms at different speeds. The dependence of grain size on the flow stress at DR in the alloy based on Ti-Si system correspond to the dependence of D ~ ?-1,2. Superplasticity is realized in a more narrow range of values of the Zener - Holomon's parameter than DR one. Superplasticity is observed when refinement structure in DR and is to increase the stability of deformation. It is no necking tensile and elongation increases, increases speed dependence of the flow stress which is reduced about in two times. Poligonization is relief from a high SFE reduces the softening initiation temperature in the alloy Zr-3,2Cr. The activation energy of the process that causes softening is correspond to the value of the activation energy of dislocation rearrangements (H = 0.4 eV). DP is occurred in the alloy of Zr-3,2 at. % Cr. Structural superplasticity effect is not observed. Formed with the substructure of large-border due to the dissolution of intermetallic particles on dislocations in the alloy of Zr-1,65Cr. It is shown that the initiation of the second phase particles of the DR (Ti-17Al-1,5Zr-1,9Si) and DP (3 Zr- 3,2Cr) leads to suppressing of the SD-effect and an increase in ductility compared with alloys without particles. It was proposed to use effect of DR in the presence of solid particles of the second phase for mechanical thermal treatment. It would be obtained large stretchings, fine-grained, non-porous structure with relatively low deformation temperatures.