S. L. Demakov

Bio: S. L. Demakov is an academic researcher from Ural Federal University. The author has contributed to research in topics: Alloy & Titanium alloy. The author has an hindex of 7, co-authored 40 publications receiving 154 citations.

Unusual Young׳s modulus behavior in ultrafine-grained and microcrystalline copper wires caused by texture changes during processing and annealing

Abstract: Effect of annealing on the dynamic Young׳s modulus E of ultrafine-grained (UFG) and microcrystalline (MC) copper obtained by combined severe plastic deformation (SPD) including repeated hydrostatic extrusion and drawing (UFG copper) or only repeated drawing (MC copper) is investigated. It is established that the Young׳s modulus in the SPD-prepared UFG and MC samples exceeds that in the coarse-grained fully annealed (CGFA) samples by 10% to 20%. Subsequent isothermal annealing at elevated temperatures between 90 and 470 °С leads to a sharp decrease of the Young׳s modulus for annealing temperatures above 210 °С. After annealing at 410 °С, the value of E reaches its minimal value that is 35% lower than E in CGFA samples (total change in E is about 50% of the initial value). Further annealing at higher temperatures leads to some increase in the Young׳s modulus. It is shown that the unusual behavior of the Young׳s modulus is caused by the formation of the 〈111〉 axial drawing texture in the SPD-treated samples which is replaced by the 〈001〉 annealing texture during the post-SPD heat treatments.

Effect of annealing temperature on the texture of copper wire

Abstract: It has been found by textural analysis methods that, in the course of annealing with heating and cooling at a rate of 100 K/s, the textured state of an oxygen-containing copper wire of grade M00 deformed by drawing to 97% reduction changes, retaining the zonal structure. In the central zone, at a relative current radius from 0 to 0.3, the 〈111〉 orientation dominates to a temperature of 300°C. At the higher temperatures, the 〈100〉 orientation becomes dominant and remains up to 500°C. At relative current radii of 0.6–1.0 (peripheral zone) and 0.3–0.6 (intermediate zone), the dominant 〈100〉 orientation is retained to 300°C; at the higher temperatures, the dominance of the 〈100〉 orientation levels off. As the annealing temperature increases, the intermediate zone wedges out at the expense of growth of the central and peripheral zones. On the whole, the annealing at high temperatures (above 400°C) leads to the predominance of the 〈100〉 orientation; it is highly dominant for relative radii of 0–0.5.

Fiber vs Rolling Texture: Stress State Dependence for Cold-Drawn Wire

Abstract: The texture of the cold-drawn copper wire was investigated along the radius using electron backscatter diffraction. The complex fiber texture of the central region of the wire was considered as the rolling texture consisting of a set of preferred orientations. The texture of the periphery region was revealed to be similar to the shear texture. The orientation-dependent properties of the wire were proven to be determined by the texture of the near-surface layers.

Structural and phase transformations in a quenched two-phase titanium alloy upon cold deformation and subsequent annealing

Abstract: Methods of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry have been used to study the formation of the structure and phase composition upon the cold rolling of rodlike semi-finished products of the VT16 alloy quenched for martensite (Tq = Tpt − 10 K). It has been established that, with an increasing degree of elongation caused by rolling in the range under investigation, a more complete deformation-induced transformation occurs according to the scheme α″ → (α′ + βa) with the formation of a βa solid solution with an anomalously large lattice parameter because of the development of accommodation processes due to the difference in the specific volumes of the initial (α″) and arising (α′) martensitic phases. A correlation between the phase composition and the microhardness and elastic characteristics has been established. The temperature intervals of the occurrence of the processes of solid-solution decomposition have been determined upon the continuous heating in the quenched and cold-rolled states.

Martensite Formation and Decomposition during Traditional and AM Processing of Two-Phase Titanium Alloys—An Overview

Abstract: Titanium alloys have been considered as unique materials for many years. Even their microstructure and operational properties have been well known and described in details, the new technologies introduced—e.g., 3D printing—have restored the need for further research in this area. It is understood that martensitic transformation is usually applied in heat treatment of hardenable alloys (e.g., Fe alloys), but in the case of titanium alloys, it also occurs during the thermomechanical processing or advanced additive manufacturing. The paper summarizes previous knowledge on martensite formation and decomposition processes in two-phase titanium alloys. It emphasizes their important role in microstructure development during conventional and modern industrial processing.

Microtexture and anisotropy in wire drawn copper

Abstract: In many processing operations, it is critical to know the relationship between the resultant sample geometry and the distribution of crystallographic or grain orientations within the polycrystalline aggregates. The spatial variations in crystallographic texture associated with different parts of the sample geometry can influence differences in the plastic response within different regions of a sample. In this paper we present a study of such local variations in the texture (microtexture) as well as grain boundary or mesotexture associated with copper wire and its implications for micromechanical inhomogeneity within a sample volume. The unique experimental and analytical aspects of such microtexture characterization are discussed along with the issues of grain boundary structural parameters and its role in microtexture and anisotropy. The presence of differences in twin frequency in different regions of the sample is suggested as a possible source of strength anisotropy.