This study is focused on the design of new Al–Cu–Mn alloys with enhanced strength and heat resistance achieved without high-temperature exposur

Проведенное исследование было направлено на разработку новых сплавов с повышенными прочностью и термостойкостью на базе системы Al–Cu–Mn без применения операций высокотемпературной обработки. Рассмотрено 7 экспериментальных сплавов, содержащих постоянную концентрацию (2 %) магния с переменным содержанием (от 0 до 4 %) меди. Выявлено, что добавка Mn ~ 2 % практически полностью входит в состав твердого раствора алюминия. Для меди в литой структуре установлено распределение между твердым раствором алюминия и эвтектическими включениями фазы Al₂Cu. Экспериментальным путем определено, что при содержании меди в сплаве 2 и 3 % в твердом растворе алюминия содержится примерно равное количество меди – до 1,5 %. Исследована деформационная пластичность экспериментальных сплавов по режиму холодной прокатки со степенью обжатия 80 и 95 %. Установлено, что для сплавов, содержащих до 3 % меди, проведение предварительной обработки не требуется – они обладают высокой технологичностью при обработке давлением. Изучено влияние термической обработки в интервале температур отжига 200–600 °С на структурные и фазовые характеристики сплавов. Выполнена оценка упрочнения сплава в процессе многоступенчатых отжигов посредством измерения твердости. Полученные данные позволили оценить влияние меди и проанализировать термостойкость модельных сплавов. Проведены испытания на растяжение холоднокатаных листов толщиной 0,5 мм со степенью обжатия 95 % сплавов, содержащих 2 и 3 % меди. Результаты показали высокие значения свойств – в частности, сплав c добавкой 3 % меди обладает сопоставимой прочностью со сплавом 1201 в состоянии T6.

The article investigates the structure of sheets made from the Al – Ca – Mn aluminum alloy system, coated using the micro-arc oxidation (MAO) method. The alloy sheets with a composition of Al – 2.5%Ca – 1.5%Mn – 0.4%Fe –0.2%Si – 0.2%Cu – 0.8%Zn were produced through hot rolling and subsequently treated in a low-alkaline alkalinesilicate electrolyte. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were employed to assess the microstructure and phase composition during the study. The results revealed a high dispersion of the alloy structure with various phases present, such as Al4Ca and Al6(Mn, Fe). The sizes of the dispersed eutectic precipitates ranged from 1.5 to 5 micrometers. The thickness of the obtained MAO coatings was between 20 and 30 micrometers. The coating structure in the middle of the samples was uniform, without through porosity, although some isolated pores and cracks were observed. X-ray phase analysis indicated the presence of aluminum oxides in the coating, such as α-Al2O3 and η-Al2O3. Additionally, other alloying elements like calcium, potassium, and sodium were noted. An important aspect was that the structure of the alloy near the coating remained stable, indicating good adhesion between the aluminum matrix and the coating. The authors emphasize the need for further research to optimize processes for producing strong and wear-resistant coatings, especially for applications in Arctic conditions. This work lays the groundwork for developing new structural materials with multifunctional coatings that could be beneficial in various industries, including automotive and shipbuilding. The work was carried out within the framework of the RNF project 23-79-00055 “Creation of scientific bases for the development of new structural materials of reduced density with protective multifunctional ceramic-like coatings for use in transport systems of the Arctic region” (coating, SEM, XRD) and at the expense of the grant named after P. L. Kapitsa of Moscow Polytechnic University, implemented within the framework of the program “Priority 2030” (melting, casting, deformation processing). The structure study was performed using the scientific equipment of the Research Chemical and Analytical Center of SIC Kurchatov Institute.

Coatings with thicknesses of 25, 50, and 100 μm were formed in an alkaline-silicate electrolyte at a constant anodic current density of 10 A/dm² in the Soft-mode. A multi-technique approach, including SEM-EDX, XRD, EIS, and microhardness testing, was employed to characterize the coatings. The coatings with thicknesses of 50 and 100 μm consisted of three layers: a base layer, a pancake layer, and an outer porous layer. The outer layer of the coating is enriched in silicon (from electrolytes) and alloying elements of the substrate, due to the occurrence of micro-arc discharges, type-B discharges, which eject plasma containing these elements into the surface layers of the coating. Phase analysis reveals a progressive increase in the α-Al₂O₃ modification with an increase in coating thickness, which correlates with enhanced microhardness. Electrochemical testing in a 3% NaCl solution demonstrates that the 100 μm Soft-mode coating provides the highest corrosion protection, significantly outperforming both thinner coatings and Arc-mode counterparts. In the Soft-mode, small “external” discharges organize into moving groups, enabling uniform thickness build-up. A model of these discharges is proposed, interpreting them as “type B discharge light” that does not reach the surface due to the presence on the surface of the “pancake-like” layer formed by type-B discharges of a hydrogen-saturated porous outer layer.