Papers by Author: N.A. Koneva

Abstract: The present work summarizes and presents separate results obtained by the authors when investigating mesoscopic and microscopic internal stresses formed under the conditions of thermal and mechanical treatment of martensitic, pearlitic and austenitic steels. Internal stresses were investigated using the method based on the analysis of bend extinction contours. The results obtained on industrial steels were presented. The sources were described and examples of internal stresses induced by these sources were given. The nature of bending-torsion of the crystal lattice depending on the averaging volume was determined. It has been shown that in martensitic steels along with the increase in the averaging volume (carbide particle → separate martensitic lath → martensite packet→ martensitic plate → grain) the amplitude of bending-torsion of the crystal lattice decreases. The nature of distortions also changes. At large amplitudes and low volumes of averaging they are completely or partly elastic, at large volumes of averaging they are completely plastic. Thereby, distortions are fully driven by the excess dislocation density.

Abstract: The present study was conducted by transmission electron microscopy (TEM) in order to investigate the structure of multicomponent nickel-based alloy obtained by directional solidification and change in its phase composition at high-temperature annealing. All states of the alloy possessed monocrystalline structure with [001] orientation. The alloy under study contained other elements apart from Ni, such as: Al, Co, and also Mo, Cr, W, Ta, Re, and Ru. The alloy was investigated in three states after annealing for: 1) 118 h; 2) 372 h; 3) 1274 h at 1000°С. The basic phases that form the alloy were γ and γ′. In the state after annealing for 118 h Al₆(Re,Ru) phase was observed in an insignificant amount. After longer high temperature annealing new phases occurred, such as σ-phase and δ-phase, Laves phase. The structures occurring during annealing can be classified into four types: 1) quasi-cuboids, 2) anisotropic stripe structures, 3) anisotropic structures of striped type with σ-phase separation, 4) structureless zones with large two-phase areas.