113,044 research outputs found
Morphology pecularities of carbide phases in High-V cast irons
No full textMorphology pecularities of carbide phases in High-V cast irons / V. G. Efremenko [и др.] // Інноваційні ресурсозбережні матеріали та зміцнювальні технології : матеріали Міжнар. наук.-практ. конф. 6-8 червня 2012, м. Маріуполь / ДВНЗ «ПДТУ». – Маріуполь, 2012. – С. 28-29
Importance of discipline "Damage and Reliability" in reforming the curriculum of materials engineering students in the framework of TEMPUS-MMATENG project
No full textEfremenko, V. G. Importance of discipline "Damage and Reliability" in reforming the curriculum of materials engineering students in the framework of TEMPUS-MMATENG project / V. G. Efremenko // Университетская наука-2016 : в 4 т. : тез. докл. междунар. науч.-техн. конф. (Мариуполь, 19-20 мая 2016 г.) / ПГТУ. – Мариуполь, 2016. – Т. 4. – С. 17–18
Capabilities of «CES Edupack 2014» software in teaching of students in «materials engineering»
No full textEfremenko, V. G. Capabilities of «CES Edupack 2014» software in teaching of students in «materials engineering» / V. G. Efremenko // Университетская наука-2015 : в 4-х т. : тез. докл. междунар. науч.-техн. конф. (Мариуполь, 19-20 мая 2015 г.) / ГВУЗ «ПГТУ». – Мариуполь, 2015. – Т. 4. – С. 12-14
Alternative Approach for the Intercritical Annealing of (Cr, Mo, V)-Alloyed TRIP-Assisted Steel before Austempering
No full textTRIP-assisted C-Si-Mn steels are usually subjected to austempering with a preliminary intercritical annealing that is targeted at the multi-phase structure with 40-60 vol.% of proeutectoid ferrite. The kinetics and the mechanism of phase-structural transformations can be impacted due to the additional alloying of TRIP-assisted steel by the strong carbide forming elements, thus necessitating an alternative approach for the selection of intercritical annealing parameters. This issue is analyzed in the present work, which investigates the effect of the temperature of intercritical annealing on the "Structure/Properties" correlations in 0.2 wt.% C-Si-Mn-Nb steel additionally alloyed by 0.55 wt.% Cr, 0.20% Mo, and 0.11 wt.% V. The annealing temperature ranged from 770 degrees C to 950 degrees C, and austempering was performed at 350 degrees C for 20 min. It was observed that the addition of the (Cr, Mo, and V) complex significantly improved the steel hardenability. However, the annealing of steel at 770 degrees C (to gain 50 vol.% of proeutectoid ferrite) resulted in the precipitation of coarse cementite lamellas during bainite transformation, thus lowering the amount of retained austenite (RA) and decreasing the strength and ductility of the steel. At higher annealing temperatures, carbide-free bainite was formed, which presented a 2.5-3.5 times increase in the RA volume fraction and a 1.5 times increase in the RA carbon content. The optimal combination of the mechanical properties (UTS of 1040 MPa, TEL of 23%, V-notch impact toughness of 95 J/cm(2), PSE of 23.9 GPa center dot%) referred to annealing at a temperature close to the Ac-3 point, resulting in a structure with 5 vol.% ferrite and 9 vol.% RA (the residue was carbide-free bainite). This structure presented an extended manifestation of the TRIP effect with an enhanced strain hardening rate due to strain-induced martensite transformation. The impact of the alloying elements on the carbon activity in austenite served as the basis for the analysis of structure formation
On selection of rational intercritical annealing temperature of a low-alloyed trip-assisted steel
No full textEfremenko B. On selection of rational intercritical annealing temperature of a low-alloyed trip-assisted steel / B. Efremenko, Y. Chabak, V. Greshta, I. Petryshynets, A. Efremenko, W. Kaiming, M. Brykov // Неметалеві вкраплення і гази у ливарних сплавах. Збірник тез ХVІІ Міжнародної науково-технічної конференції (Запоріжжя, 26-27 листопада 2024 року). – Запоріжжя: НУ «Запорізька політехніка», 2025. – С. 35
Structural features of high-chromium cast iron surface layers decarburization under destabilizing heating
No full textStructural features of high-chromium cast iron surface layers decarburization under destabilizing heating / V. G. Efremenko [и др.] // Інноваційні ресурсозбережні матеріали та зміцнювальні технології : матеріали Міжнар. наук.-практ. конф. 6-8 червня 2012, м. Маріуполь / ДВНЗ «ПДТУ». – Маріуполь, 2012. – С. 39-40
Chemical composition of Laves phase in 718 inconel-type LPBF alloy modified by surface laser melting
No full textEfremenko B. Chemical composition of Laves phase in 718 inconel-type LPBF alloy modified by surface laser melting / B. Efremenko, A. Lekatou, V. Efremenko, Y. Chabak, K. Wu, S. Arshad, E. Balalaeva // Неметалеві вкраплення і гази у ливарних сплавах. Збірник тез ХVІІ Міжнародної науково-технічної конференції (Запоріжжя, 26-27 листопада 2024 року). – Запоріжжя: НУ «Запорізька політехніка», 2025. – С. 90-91
Austempering vs. Q&P: Comparative effects on microstructure and mechanical properties of complex-alloyed TRIP-assisted steel
No full textThis study compares the effect of austempering (AT) and two-step quenching and partitioning (Q&P) treatments on the microstructure and mechanical properties of a 0.2 wt% C Mn-Si-Cr-Mo-V-Nb TRIP-assisted steel. Both treatments included austenitization (770 °C or 900 °C) followed by quenching and isothermal holding (20 min). AT used a 350 °C isothermal hold, while Q&P involved quenching to 200 °C or 230 °C, followed by partitioning at 350 °C. Microstructural analysis (OM, SEM, XRD, EPMA, EBSD) revealed ferrite and (Nb,V)C in both treatments, with bainite (AT) or tempered martensite/bainite (Q&P) and varying retained austenite (RA) content depending on the austenitization temperature. Austenitization at 770 °C resulted in Cr- and Mo-promoted cementite precipitation, reducing the RA volume fraction and ductility. In contrast, 900 °C austenitization resulted in a cementite-free structure with 7–9 vol% RA exhibiting a clear TRIP effect. The ultimate tensile strength (UTS) increased with austenitization temperature (820–880 MPa to 1040–1090 MPa) due to a decreased proeutectoid ferrite, grain refinement, and enhanced TRIP effect, though at some expense of ductility/toughness. Under the same austenitization parameters, Q&P yielded slightly higher UTS (∼ 50 MPa higher), and much greater impact toughness (by 2 times at 770 °C and 1.4 times at 900 °C). Due to a superior strength-ductility-toughness balance, Q&P is identified as a more promising heat treatment for this TRIP-assisted steel
Effect of quenching temperature on hardness and three-body-abrasion wear resistance of hybrid multi-component cast irons
No full textEfremenko V. Effect of quenching temperature on hardness and three-body-abrasion wear resistance of hybrid multi-component cast irons / V. Efremenko, Y. Chabak, M. Golinskyi, I. Petryshynets, V. Kudin, K. Shimizu, D. Zaitsev // Неметалеві вкраплення і гази у ливарних сплавах. Збірник тез ХVІІ Міжнародної науково-технічної конференції (Запоріжжя, 26-27 листопада 2024 року). – Запоріжжя: НУ «Запорізька політехніка», 2025. – С. 52-55
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
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