Abstract
The article presents original experimental data on surface tension of the Fe100 –xMnx (x = 4–13 wt %) melts. Surface tension and density of the melt were measured by the sessile drop method at heating from the liquidus temperature to 1780°C and subsequent sample cooling in the atmosphere of high-purity helium. Temperature and concentration dependences of surface tension and density of Fe–Mn melts were plotted. Manganese is a surface-active substance in iron melt. The value of surface tension coefficient of Fe–Mn melts decreases as Mn content increases. Experimental data on the surface tension of Fe–Mn melts is consistent with the theoretical dependences (the Pavlov–Popel’ equation and the Shishkovsky equation). During the investigation of Fe–Mn melt microheterogenity, correlation between the values of kinematic viscosity, surface tension, and density is revealed. Fluidity dependence of Fe–Mn melts on their density in the cooling mode has a linear character which indicates satisfaction of the Bachinskii law. Discrepancy in the melt viscosity ratios to the surface tension coefficient obtained from the experimental data and from the empirical formula is discovered. Using the experimental data on viscosity and surface tension of Fe–Mn melts, the entropy change in the melt’s bulk and the change in the melt’s surface entropy, respectively, are studied. The surface entropy and the bulk entropy in the melt decrease in their absolute value with its increasing Mn content. From the study results, it is concluded that there is no destruction of the microheterogeneous structure of Fe100 –xMnx (x = 4–13 wt %) melts when heated up to 1780°C.
Highlights
Surface tension and density of the melt was measured by the method of sessile drop at heating from the liquidus temperature up to 1780 °C and subsequent cooling of the sample in the atmosphere of high-purity helium
The value of surface tension coefficient of Fe – Mn melts decreases while Mn content increases
Experimental data on the surface tension of Fe – Mn melts is consistent with the theoretical dependences (Pavlova-Popiel equation and the Shishkovsky equation)
Summary
Сплавы Fe – Mn с содержанием марганца 4, 6, 8, 10 и 13 вес. % были получены в лабораторных условиях в защитной атмосфере высокочистого гелия при нагреве до температуры 1600 °С с последующим охлаждением со скоростью ~1 °С/с. Химичес кий состав образцов определен с помощью спектромет ра SPECTROMIDEX (SPECTRO Analytical Instruments GmbH, Germany). Поверхностное натяжение измеряли методом сидящей капли в режиме нагрева до 1780 °С и последующего охлаждения образца. Затем запускали гелий до давления ~105 Па. Образцы выдерживали в камере с инертной средой в течение 5 – 8 мин при температуре плавления, затем производили нагрев до 1780 °С с шагом 30 °С. Изотермические выдержки в точках отсчета составляли не менее 15 мин. Профиль исследуемой капли снимали цифровой фотокамерой с копированием изображения на компьютер, геометрические размеры профиля капли определяли с помощью программы анализа изображений SIAMS 700 с точностью 0,3 – 0,6 град. Погрешность определения значений поверхностного натяжения не превышала 7 %. Метод измерения поверхностного натяжения металлических расплавов (метод сидящей капли) и установка для его реализации описаны в работах [18 – 19]
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