Статті КТОМП (ДМетІ)

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Determination of Bronze БрА7К2О1,5Мц0,3 Crystallization Interval Limit Values and Phase Transformations
(Dnipro University of Technology, Dnipro, 2025) Kimstach, Tetiana V.; Uzlov, Kostiantyn I.; Bilyi, Oleksandr P.; Solonenko, Liudmyla I.; Repyakh, Serhii I.
ENG: Phase transformations temperatures, crystallization intervals, etc. are any alloy’s fundamental parameters. Alloys’ casting, technological and operational properties are related to them. Nevertheless, unlike two-component bronzes, such requirements for multi-component structural, non-magnetic, corrosion-resistant bronze БрА7К2О1,5Мц0,3 are absent. Purpose. For Cu-Al-Si-Sn-Mn system bronzes, crystallization intervals quantitative values (liquidus and solidus temperatures, crystallization interval size and solid phase relative share in it) have been established. БрА7К2О1,5Мц0,3 bronze’s alloying components’ synergistic and selective influence on its crystallization interval and relative fluidity indicators changing has been determined. Methodology. Well-known methods and research techniques, including thermography, differential thermal analysis, spectral chemical analysis, images analysis digital method have been used in this work. Bronzes fluidity has been assessed using spiral test. Bronze’s alloying elements’ synergistic and selective influences on its characteristics have been determined using chemical elements ratio in it (KR criterion) and experimental data results processing by Excel computer program. Findings. In bronze БрА7К2О1,5Мц0,3 with KR criterion value rising from 0.35 to 0.84, there increase liquidus, solidus temperatures and crystallization interval from 32 to 49 °C. Bronze’s alloying elements’ (Al, Si, Sn, Mn) synergistic and selective influences on its crystallization interval limit values have been determined. It has been established that conditionally-veritable fluidities of БрА7К3О1,5Мц0,3 and БрА9Ж3Л bronzes are practically the same. For Cu-Al-Si-Sn-Mn system bronzes with KR = 0.35‒2.07, solid phase relative volume fraction (φSP) in crystallization temperature range is 60‒63 %. Originality. For the first time, limiting values and phase transformations for БрА7К2О1,5Мц0,3 bronze’s crystallization interval and alloying elements synergistic and selective influence on these indicators have been determined. Practical value. Based on БрА7К2О1,5Мц0,3 bronze’s chemical composition selected, mathematical models have been proposed for its liquidus and solidus temperatures calculating and for transition from dependences of solid phase t(φSP) volume fraction in crystallization temperature range to temperatures’ absolute values t(φSP). Their use will allow increasing the indicators of foundry and technological parameters accuracy forecasting.
Influence of Ice Structure on Vitability of Frozen Sand-Water and Sand-Clay Mixtures
(Dnipro University of Technology, Dnipro, Ukraine, 2024) Solonenko, Liudmyla I.; Uzlov, Kostiantyn I.; Kimstach, Tetiana V.; Mianovska, Yana V.; Yakymenko, D. Yu.
ENG: Purpose. To establish influence regularity of sand, water and clay preparation conditions on vitability of frozen mixtures made from combinations of these components and to increase the castings quality in foundries, as well as to improve technologies for artificial freezing of soils for underground constructions. Methodology. In this research, sand, clay, and water are used. Ice quality is estimated visually after water freezing at -15 °C in glass tubes. Frozen mixtures’ vitability at -15 °C is studied on beam-type samples. As indicators of survivability, the time to 1 mm bending of samples on supports and the time to their destruction are accepted. The time is recorded with a stopwatch, the temperature with an alcohol thermometer, the mass with electronic scales and the deflection arrow with a clock-type indicator. Findings. The presence and amount of water-soluble impurities in rare water significantly influence the nature, size and distribution of gas bubbles in ice, as well as frozen sand-water mixtures vitability. Frozen mixtures’ survivability increases with water content in them increasing, and, for sand  water mixtures, survivability is maximum if ice has a homogeneous structure. Among mixtures with clays, the mixture with non-swollen kaolin clay has the greatest vitability. Regarding survivability, recommendations for manufacturing products from frozen foundry mixtures have been developed. Originality. For the first time, deformation change kinetics (bending arrows) under the influence of beam-type samples’ self-mass from mixtures of quartz sand and water and quartz sand, clay and water frozen at -15 °C, which have been previously prepared in different ways, have been investigated. Insights into the influence of various factors and ice quality on the vitability of frozen mixtures have been further developed. Practical value. The obtained results can be useful for expanding ideas about natural frozen soils’ behavior during their cyclic temperature changes, soils artificially frozen during mine shafts elaboration, escalators’ and junctions’ tunnels, etc. when constructing subways. In foundries, the developed recommendations will reduce technological losses and will improve casting quality made using frozen casting molds and cores from sand-water or sand-clay-water mixtures, castings’ patterns and their pouring systems from sand-water mixtures.