Probe microscopy in the study of the surface of aluminum alloys

The work was supported by the Grant of the RNF 14-19-01033-P (study of topography and elemental composition of the surface) and the State Task (№ State registration AAAA-A17-117021310379-5 - study of electrical properties of the surface). The authors are grateful to N.A. Belov (MISiS) for providing samples

Phase Composition and Microstructure of Cast Al-6%Mg-2%Ca-2%Zn Alloy with Fe and Si Additions

Data Availability Statement: Not applicable.Investigating the effect of Fe and Si is essential for any new Al-based composition, as these impurities can be easily found both after primary production and recycling. This study is dedicated to filling the gap in revealing the phase composition of an Al-6%Mg-2%Ca-2%Zn alloy after the combined and separate addition of Fe and Si. This was addressed by permanent mold casting and solid solution heat treatment. The investigation of slowly solidified samples also contributed to understanding potential phase transitions. It was found that the alloy containing 0.5%Fe can have nearly spherical intermetallics after heat treatment, whereas a higher Fe content brought the formation of a needle-shaped Al3Fe intermetallic. We explain this by the formation of a ternary α-Al + Al10CaFe2 + Al4Ca eutectic, which is more compact in as-cast condition compared to divorced binary α-Al + Al4Ca and α-Al + Al3Fe eutectics. Similarly, 0.5%Si readily incurred the formation of a needle-shaped Al2CaSi2 intermetallic, probably also by a binary reaction L → α-Al + Al2CaSi2. In the solidified samples, no Mg2Si phase was found, even in slowly solidified samples. This is contrary to the thermodynamic calculation, which suggests a peritectic reaction L + Al2CaSi2 Mg2Si. Interestingly, the addition of 0.5%Si caused an even coarser microstructure compared to the addition of 1%Fe, which caused the appearance of a primary Al3Fe phase. We conclude that the new alloy is more tolerable to Fe rather than Si. Specifically, the addition of 0.5%Fe can be added while maintaining a fine morphology of the eutectic network. It was suggested that the morphology of eutectic and solid solution hardening governed the mechanical properties. The strength of the alloys containing separate 0.5%Fe (UTS = 215 ± 8 MPa and YS 146 ± 4 = MPa) and the combined 0.5%Fe and 0.5%Si additions (UTS = 195 ± 14 MPa and YS ± 1 = 139 MPa) was not compromised compared to the alloy containing 0.5%Si (UTS 201 ± 24 = MPa and YS = 131 ± 1 MPa).Russian Science Foundation (Project No. 23-79-01055 https://rscf.ru/project/23-79-01055/) (SEM, XRD analysis, hardness, tensile tests); Moscow Polytechnic University within the framework of the grant named after Pyotr Kapitsa (Conceptualization, SEM, TEM, Thermo-Calc calculations, discussion); the results were obtained by using the equipment of the Center for Collective Use, “Materials Science and Metallurgy”, with the financial support of the Ministry of Science and Higher Education of the Russian Federation (#075-15-2021-696)

Влияние висмута и свинца на фазовый состав и структуру сплава Al–5%Si–4%Cu–4%Sn

The article focuses on the actual problem of creating economically alloyed antifriction aluminum alloys doped with low-melting metals. It was found in earlier experiments that an alloy containing about 5 % Si, 4% Cu and 6 % Sn (wt.%) has a balanced complex of technological and physicomechanical properties. Due to the high cost of tin, this paper considers the possibility of reducing its concentration to 4 %, and its partial replacement by other low-melting metals, such as bismuth and lead. Thermodynamic calculations (in the Thermo-Calc program) including the construction of polythermal and isothermal sections are used to study the joint and separate influence ofthese elements on the phase composition of the Al—5%Si—4%Cu—4%Sn alloy. It is shown that the addition of lead and bismuth leads to the appearance of an extensive area of fluid separation, and therefore their total concentration should not exceed 1—2 %. The phase composition and microstructure ofthe Al—5%Si—4%Cu—4%Sn—0,5%Pb—0,5%Bi alloy were studied using scanning electron microscopy and micro X-ray spectral analysis. It was found that in the cast state, low-melting metals are evenly distributed in the structure of the alloy, and in terms of the combination of properties, the experimental aluminum alloys surpass the BrO4Z4S17 antifriction bronze. Heat treatment mode T6 leads to a significant increase in the hardness of the experimental alloy. However, in the process of heating for quenching at 500 °C, local fusion of the low-melting component occurs, which leads to deterioration of the microstructure upon re-crystallization and, as a result, causes alloy embrittlement.Статья посвящена актуальной на сегодняшний день проблеме создания антифрикционных алюминиевых сплавов, экономнолегированных легкоплавкими металлами. В ранних исследованиях было установлено, что сбалансированным комплексом технологических и физико-механических свойств обладает сплав, содержащий, мас.%: около 5 Si, 4 Cu и 6 Sn. В данной работе в связи с высокой стоимостью олова рассмотрена возможность снижения его концентрации до 4 % и его частичной замены другими легкоплавкими металлами, такими как висмут и свинец. С использованием термодинамических расчетов в программе Thermo-Calc, включая построение политермических и изотермических разрезов, было изучено совместное и раздельное влияние этих элементов на фазовый состав сплава Al—5%Si—4%Cu—4%Sn. Показано, что добавки свинца и висмута приводят к появлению обширной области расслоения жидкости, в связи с чем их суммарная концентрация не должна превышать 1—2 %. С использованием сканирующей электронной микроскопии и микрорентгеноспектрального анализа изучены фазовый состав и микроструктура сплава Al-5%Si—4%Cu—4%Sn-0,5%Pb—0,5%Bi. Выявлено, что в литом состоянии легкоплавкие металлы распределены равномерно в структуре экспериментального сплава, а по совокупности свойств этот материал превосходит антифрикционную бронзу БрО4Ц4С17. Термическая обработка по режиму Т6 приводит к существенному повышению твердости исследуемого сплава. Однако в процессе нагрева под закалку при 500 °С происходит локальное оплавление легкоплавкой составляющей, что обуславливает ухудшение микроструктуры при повторной кристаллизации и, как следствие, служит причиной охрупчивания материала