Abstract:The replication casting process is used for manufacturing open-pore aluminum foams with advanced performances, such as stability and repeatability of foam structure with porosity over 60%. A simple foam structure model based on the interaction between sodium chloride solid particles poorly wetted by melted aluminum, which leads to the formation of air pockets (or "air collars"), is proposed for the permeability of porous material. The equation for the minimum pore radius of replicated aluminum foam is derived. According to the proposed model, the main assumption of the permeability model consists in a concentration of flow resistance in a circular aperture of radius r min . The permeability of aluminum open-pore foams is measured using transformer oil as the fluid, changing the fractions of initial sodium chloride. Measured values of minimum pore size are close to theoretically predicted ones regardless of the particle shape. The expression for the permeability of replicated aluminum foam derived on the basis of the "bottleneck" model of porous media agrees well with the experimental data. The obtained data can be applied for commercial filter cells and pneumatic silencers.

The new technology of producing ingot of AlSi7Fe1 high-strength is described. This new technology consists in saturation of melt with hydrogen, with further blowing with oxygen. Studied the microstructure, phase composition and mechanical properties of ingot after blowing oxygen of melt and ingot obtained with the traditional method. Have suggested that in liquid aluminum alloy AlSi7Fe1 because of blowing with oxygen arise refractory particles Al2O3. These particles Al2O3 further in crystallization serve as a modifier of the microstructure of ingot. Mostly observed modifications of eutectic phases. Thus saturation of melt with hydrogen, with further blowing with oxygen provides an increased tensile strength of ingot AlSi7Fe1.

The technology of producing a composite material in situ envisages the pre-saturation of an AlSi7Fe1 melt with hydrogen; afterwards, the melt is blown with oxygen until the hydrogen dissolved in the melt is burned out. The hydrogen content was researched during the manufacturing process of the composite material; before oxygen blowing, and at incomplete and complete burning out of the dissolved hydrogen. The interrelation between the absorbed hydrogen content and the aluminum oxide fraction was identified. A mathematical model was proposed which demonstrated that during the saturation process of the melt with oxide particles, hydrogen was absorbed on their surface as a layer close to monoatomic, which does not lead to the realization of the pores’ heterogeneous nucleation mechanism. Due to this, castings produced from the researched composite material are leakless. Incomplete burning out of hydrogen dissolved in the melt leads to the formation of significant hydrogen porosity. The proposed method of prevention of gas porosity in cast composites is an alternative to the conventional one and offers not only the purging of the melt from oxide inclusions but, on the contrary, a significant increase in their specific surface, which allows for the reduction in hydrogen content on the inclusion surface to the monoatomic level.

One of the main goals of modern materials research is obtaining different microstructures and studying their influence on the mechanical properties of metals; aluminum alloys are particularly of interest due to their advanced performance. Traditionally, their required properties are obtained by alloying process, modification, or physical influence during solidification. The present work describes a saturation of the overheated AlSi7Fe1 casting alloy by oxides using oxygen blowing approach in overheated alloy. Changes in metals’ microstructural and mechanical properties are also described in the work. An Al10SiFe intermetallic complex compound was obtained as a preferable component to Al2O3 precipitation on it, and its morphology was investigated by scanning electron microscopy. The mechanical properties of the alloy after the oxygen blowing treatment are discussed in this work.

Приведены результаты сравнительного исследования коррозионной стойкости алюмоматричного композита, полученного методом продувки кислородом предварительно гидрогенизированного расплава на основе сплава Al-Si-Fe с содержанием железа более 1 %, предназначенного для литья под давлением, и сплава Al-7Si с 0,3 % Fe, модифицированного лигатурой 5Al-Ti в количестве 2 %. Коррозия в алюминиевых сплавах обусловлена нарушением сплошности оксидной пленки на некоторых фазах, прежде всего на фазе Al 5 SiFe. Пары образцов из композита и сплава сравнения диаметром 15 мм и длиной 50 мм подверглись испытаниям в 7 %-ном растворе солевого тумана NaCl в камере КСТ-1 на подвесках при температуре 22 °С в течение 300 ч. Полученные результаты показали близкие значения убыли массы образцов, несмотря на значительно более высокое содержание железа в материале, поскольку сформировавшиеся в расплаве при продувке кислородом частицы Al 2 O 3 размером 100-200 нм, осаждаясь на границах фаз, снижают площадь поверхности взаимодействия с коррозионной средой. Литературные данные показывают существенное отличие сопротивления коррозионному воздействию композитов ex situ от in situ вследствие различий в размерах и расположении в матрице упрочняющей фазы. Исследованный композиционный материал может быть рекомендован как коррозионно-стойкая альтернатива сплавам с повышенным содержанием железа, используемым для литья под давлением.