E. V. Naydenkin

Influence of equal-channel angular pressing on the structure and mechanical properties of low-carbon steel 10G2FT

Results are presented of the investigation of mechanical properties, microstructure, and phase composition of low-carbon steel 10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) before and after equal-channel angular pressing (ECAP). It has been established that the ECAP of steel 10G2FT at T = 200°C in the case of the ferritic-pearlitic state and at T = 400°C in the case of the martensitic state leads to the formation of a predominantly submicrocrystalline structure with an average size of structural elements of approximately 0.3 μm, causes an increase in the strength properties, a decrease in the plasticity, and the localization of plastic flow. It has been experimentally shown that the initially martensitic structure after ECAP causes higher strength properties in comparison with the ferritic-pearlitic structure.

The influence of temperature on microstructure and microhardness in high-pressure torsion of low-carbon steel

The ultrafine-grained structures produced by cold (20 ?C) and warm (450 ?C) high- pressure torsion in low-carbon steel were studied using transmission electron microscopy and X-ray analysis. After cold high-pressure torsion, the size of fragments is smaller (100 nm) and structure is more homogeneous in comparison with warm deformation (120 nm). As a result of high-pressure torsion, the microhardness of steel investigated has been increased up to 600 HV and 570 HV after cold and warm deformation respectively.

Microstructural Characterization of Low-Carbon Steel Processed by High Pressure Torsion and Annealing

Ultrafine grained low carbon steel processed by high pressure torsion (HPT) has been investigated. Depending on initial state (ferritic-pearlitic state after normalization at 950°C, or martensitic ones after quenching from 950°C and 1180°C), the evolution of the microstructure and the mechanical properties was investigated after HPT and annealing at 400-600°C using transmission electron microscopy and X-ray analysis. It has been shown that HPT of martensitic low carbon steel provides a finer structure then that for ferritic-pearlitic initial state, and the initial martensitic morphology and phase composition is strongly dependent on the temperature of quenching. The initial structure was refined by HPT to 95nm in ferritic-pearlitic state and up to 65 and 50 nm in martensitic ones (after quenching from 950°C and 1180°C, respectively). Such ultrafine grained structures demonstrate substantial mechanical properties and possess a high thermal stability up to 500°C in all investigated states. Annealing for 1 h at 500°C results in grain growth up to 860nm for ferritic-pearlitic initial state and 150-450 nm for martensitic ones.

Effect of high-temperature annealing on the microstructure and mechanical properties of ferritic-pearlitic steel 10G2FT subjected to equal-channel angular pressing

Results are given of the investigation of mechanical properties, microstructure, and phase composition of low-carbon ferritic-pearlitic steel 10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) after equal-channel angular pressing and subsequent high-temperature annealing at temperatures of 500–700°C. It has been shown that the predominantly submicrocrystalline structure formed during the equal-channel angular pressing possesses high thermostability up to a temperature of 500°C. The contribution of age hardening to the strengthening of steel 10G2FT during the equal-channel angular pressing and to the stabilization of the submicrocrystalline structure to high annealing temperatures is discussed.

The Effect of Grain Boundary State on Deformation Process Development in Nanostructured Metals Produced by the Methods of Severe Plastic Deformation

In this review the investigations of deformation process development are discussed which were carried out by tension and creep in the temperature range Т<0.4Tm (here Тm is the absolute melting point of material) for nanostructured metals produced by the methods of severe plastic deformation. The contribution of grain boundary sliding to the total deformation in the above temperature interval is also considered. An analysis is made of the effect of grain size and grain boundary state on the evolution of grain boundary sliding and cooperative grain boundary sliding in nanostructured metals.

Deformation Behavior and Plastic Strain Localization of Nanostructured Materials Produced by Severe Plastic Deformation

The literature on the deformation behavior and plastic strain localization inherent to nanostructured metallic polycrystals produced by severe plastic deformation techniques is reviewed. The effects of the texture, structure heterogeneity and state of grain boundaries on the special features and evolution of mesoscopic and macroscopic localized deformation bands are investigated. The role of grain-boundary sliding in the development of mesoscopic plastic deformation bands is discussed.

The Features of Deformation Behavior of Ultra-Fine Grained Titanium and Aluminum Alloys under Conditions of High Strain Rate Superplasticity

The stress-strain curves at high strain rate superplasticity were analyzed for Ti-6Al-4V and aluminum 1420 industrial alloys in ultra-fine grained state produced by severe plastic deformation. For both alloys the observed strengthening effect can be caused by grain growth under the above mentioned conditions resulting to increase of grain boundary sliding resistance. In the case of aluminum alloy the grain recovery can be accompanied by significant change in phase composition which is also stimulates the recrystallization process.

The Evolution of Structure and Mechanical Properties of Fe-Mn-V-Ti-0,1C Low-Carbon Steel Subjected to Severe Plastic Deformation and Subsequent Annealing

The present work deals with the evolution of mechanical properties and structure of low-carbon Fe-1,12Mn-0,08V-0,07Ti-0,1C (wt.%) steel after severe plastic deformation (SPD) and high-temperature annealing. Steel in initial ferritic-pearlitic state was deformed by equal channel angular pressing (ECAP) at T=200°C and high pressure torsion (HPT) at room temperature. The evolution of ultrafine grained structure and its thermal stability were investigated after annealing at 400-700°C for 1 hour. The results shown that SPD leads to formation of structure with an average size of (sub-) grain of 260 nm after ECAP and 90 nm after HPT. Ultrafine grained structures produced by SPD reveal a high thermal stability up to 500°C after ECAP and 400°C after HPT. At higher annealing temperatures a growth of structural elements and a decrease in microhardness were observed.

Evolution of grain–subgrain structure and carbide subsystem upon annealing of a low-carbon low-alloy steel subjected to high-pressure torsion

The effect of annealing on the evolution of an ultrafine-grain structure and carbides in a 06MBF steel (Fe–0.1Mo–0.6Mn–0.8Cr–0.2Ni–0.3Si–0.2Cu–0.1V–0.03Ti–0.06Nb–0.09C, wt %) has been studied. The grain–subgrain structure (d = 102 ± 55 nm) formed by high-pressure torsion and stabilized by dispersed (MC, M3C, d = 3–4 nm) and relatively coarse carbides (M3C, d = 15–20 nm) is stable up to a temperature of 500°C (1 h) (d = 112 ± 64 nm). Annealing at a temperature of 500°C is accompanied by the formation in regions with a subgrain structure of recrystallized grains, the size of which is close to the size of subgrains formed by high-pressure torsion. The average size and distribution of dispersed particles change weakly. The precipitation hardening and the increase in the fraction of high-angle boundaries in the structure cause an increase in the values of the microhardness to 6.4 ± 0.2 GPa after annealing at 500°C as compared to the deformed state (6.0 ± 0.1 GPa). After 1-h annealing at 600 and 700°C, the microcrystal size (d = 390 ± 270 nm and 1.7 ± 0.7 μm, respectively) increases; the coarse M3C (≈ 50 nm) and dispersed carbides grow by 5 and 8 nm, respectively. The value of the activation energy for grain growth Q = 516 ± 31 kJ/mol upon annealing of the ultrafine-grained steel 06MBF produced by high-pressure torsion exceeds the values determined in the 06MBF steel with a submicrocrystalline structure formed by equal-channel angular pressing and in the nanocrystalline α iron.

Effect of Grain Boundary State on Diffusion and Diffusion-Controlled Processes in Ultrafine-Grained Materials Processed by Severe Plastic Deformation

Experimental studies on the grain boundary diffusion and processes controlled by it in the ultrafine-grained metallic materials produced by various methods of severe plastic deformation are reviewed. Correlation between the increased diffusion permeability of grain boundaries and features of recrystallization and deformation development in these materials possessing the non-equilibrium state of grain boundaries formed during severe plastic deformation in the temperature range of T < 0.35Tm is demonstrated and analyzed.