Marina M. Abramova

Microstructure Evolution in a Cu-0.5Cr-0.2Zr Alloy Subjected to Equal Channel Angular Pressing, Rolling or Aging

The evolution of microstructure in the Cu-0.5%Cr-0.2%Zr alloy subjected to thermomechanical treatment has been studied by means of the x-ray analysis. The workpieces have been subjected to 1, 2, 4 and 8 passes of equal channel angular pressing, plain cold rolling and aging treatment. The results of the XRD investigations reflect the evolution of the lattice parameter, the size of coherently scattering domains, the elastic microdistortions and the dislocation density in Cu matrix. The observed changes in the microstructure are explained by the competition between the developing defects and precipitation of the Cr phase particles from the Cu matrix.

Microstructure, properties, and failure characteristics of medium-carbon steel subjected to severe plastic deformation

The paper deals with two-stage processing of medium-carbon steel 45 (0.45 % C; 0.27 % Si; 0.65 % Mn) via quenching and high pressure torsion. Such processing combination allowed producing a nanocomposite microstructure with a ferrite matrix and high-dispersed carbides. The ultimate tensile strength of the nanostructured steel is over 2500 MPa. The processing effect on the structure, mechanical properties and failure mechanisms of steel 45 samples is studied. The peculiarities of static fractures in the samples after HPT are demonstrated in comparison with those after quenching.

The Effect of Structure on Mechanical and Corrosion Properties of Austenitic Steel Subjected to Neutron Irradiation

The initial and deformed states of austenitic stainless steel AISI 321 before and after neutron irradiation with a damage dose up to 5.3 dpa at reactor core temperature of 350 °С were comparatively investigated. Corrosion behavior, mechanical properties are analyzed in the temperature range of 20…650 °С. It is shown that radiation damage of the steel in the deformed state significantly decreases in comparison with the initial coarse-grained state at the same level of corrosion resistance.

Superior Strength and Multiple Strengthening Mechanisms in Nanocrystalline TWIP Steel

The strengthening mechanism of the metallic material is related to the hindrance of the dislocation motion, and it is possible to achieve superior strength by maximizing these obstacles. In this study, the multiple strengthening mechanism-based nanostructured steel with high density of defects was fabricated using high-pressure torsion at room and elevated temperatures. By combining multiple strengthening mechanisms, we enhanced the strength of Fe-15 Mn-0.6C-1.5 Al steel to 2.6 GPa. We have found that solute segregation at grain boundaries achieves nanograined and nanotwinned structures with higher strength than the segregation-free counterparts. The importance of the use of multiple deformation mechanism suggests the development of a wide range of strong nanotwinned and nanostructured materials via severe plastic deformation process.

Corrosion-Resistance of MAO-Coatings on Al-Si Alloys

The results of the experimental study of the influence of micro-arc oxidation (MAO) on the corrosion resistance of aluminum alloy samples AK12D are presented in this paper. The description of the research methodology, including the formation of the hardened layer on the surface of laboratory samples by MAO under various process conditions and the study of their corrosion resistance are given. The studies were conducted in accordance with the experimental design theory for fractional factorial experiment 23-1. The MAO process was carried out using an alkaline electrolyte. MDO process factors were chosen according to an electrolyte concentration of the components (caustic potash - KOH and water glass - Na2SiO3) and electrical parameters of the process determined by the capacitors capacitance. In addition to corrosion resistance of the samples, the thickness, porosity, and microhardness of MAO layer were determined. Regression equations and conclusions about the degree of influence of modes of micro-arc oxidation on the corrosion resistance of the samples were compiled on the basis of the data obtained. The results showed that the MAO process regimes have a significant effect on the corrosion resistance of the samples. Regression equations describing the effect of the thickness and porosity of the surface on the corrosion rate are derived. It has been found that the greatest influence on the corrosion resistance renders the mean value of porosity. With an increase of this parameter there is an increase in the corrosion resistance of the coating. To account for this effect, it has been suggested that the corrosion resistance of the MAO layer should not correlate with the porosity but with the absolute volume occupied by the pores in the coating. The study was conducted to investigate the prospects for the use of the MAO method for improving the corrosion properties of parts and details made of Al-Si aluminum alloys.