Acta Metallurgica Slovaca

BIOSOLUBLE MAGNESIUM-BASED ALLOYS FOR OSTEOSYNTHESIS

Viktor Greshta — 2024-03-25

The impact of micro-alloying of AZ91 and NZ30K magnesium alloys with silver and scandium to produce biosoluble implants for osteosynthesis is studied in the paper. The application of these alloys is limited due to the significant reduction of the mechanical properties of magnesium during the regeneration of fractures. It was found that the higher the concentration of the above-mentioned elements, the bigger the amount of intermetalloids that appear and the smaller they become. There were different mechanical properties observed at the sample cross-section, but the difference was successfully eliminated by thermal treatment. It reduced the chemical heterogeneity of the workpiece at the cross-section and, respectively, the value of micro-hardness. It is shown that microalloying these alloys with 0.05…0.1 % of silver and scandium ensures the grinding of the structural elements of the metal and a significant increase of the set of their properties. The research of the developed alloys showed that NZ30K alloy, which additionally contains 0,05 ... 0,1% of silver, after a three-month treatment with gelofusine saves its mechanical properties like those of the bone tissue. Pre-clinical research revealed that they are non-toxic, have an antibacterial effect and preserve the whole set of properties till the complete fracture consolidation.

MODELING OF CARBIDE FORMATION IN ALLOY OF THE Ni-Cr-Co-W-Mo-Al-Ti-C SYSTEM

Alexander Glotka — 2024-03-25

Theoretical modeling of thermodynamic processes of separation of carbide phases was carried out, as well as a practical study of the structure and distribution of chemical elements in carbides. Based on an integrated approach for the Ni-Cr-Co-W-Mo-Al-Ti-C system, new regression models were obtained that make it possible to predict the chemical composition of carbides based on the chemical composition of the alloy. A comparative assessment of the calculation results obtained using regression models and experimental data obtained by X-ray spectroscopy was carried out.

Microstructure of the P92 weld joint after 5000 h of annealing

Marek Sroka — 2024-03-25

P92 (X10CrWMoVNb9-2) is commonly used for high-pressure elements of modern power units for supercritical steam parameters. As a result, steel is characterized by good strength, corrosion and creep resistance properties at elevated temperatures.

Welded joints of pressure elements of steam boilers are potentially the weakest points in assessing their service life. Therefore, they are a place where, during long-term operation, the continuity of the material within the weld, usually in the heat-affected zone, may be lost. Therefore, material studies of welded joints on the base material contribute to the understanding of degradation processes.

The paper presents microstructure and hardness testing of P92 welded joint after 5000h of annealing at 600 and 650°C. The hardness of the material was compared to the microstructure images in the initial state and after annealing. A scanning electron microscope carried out the microstructure tests.

LOW CARBON FOOTPRINT ALUMINIUM COMPONENTS FOR E-MOBILITY

Elisa Fracchia — 2024-03-25

In the fast-evolving E‐mobility transformation, the circular economy is one of the key factors to make Europe carbon neutral by 2050, together with sustainability, achievable only with a synergic approach, from raw material choice to recycling, through product design for re‐purposing. Secondary aluminium alloys have a twenty times lower carbon footprint than primary metals, leading to significant CO₂ savings. Their properties can satisfy engineering targets through optimized product design. Adopting a smart system layout, in which functions are assigned to assemblies, some of the low‐end mechanical properties of secondary alloys can be offset. Design for easy disassembling can then guarantee a selective re‐purposing and, finally, an environmentally friendly recycling of components. Innovative products in this field have been developed and successfully produced by means of an optimized high-pressure die casting (HPDC) technology, adopting low carbon footprint raw materials supplied in alternative to ingot format. In this work, the characterization of a component for e-mobility has been conducted, evaluating both the characteristics of the scrap alloy used to produce the castings and the casting itself. The results demonstrate a fine and high-quality microstructure of the casting, proving the feasibility of the production process using exclusively scrap alloy.

MODELING THE FERROSILICOMANGANESE SMELTING PROCESS USING MANGANESE-RICH SLAG

Assylbek Abdirashit — 2024-03-25

В статье представлены результаты полного термодинамического моделирования (ТДМ) процесса выплавки стандартного ферросиликомарганца (FeSiMn) из шлаков рафинированных железомарганцевых и марганцевых руд Казахстана. Моделирование процессов и фазовых превращений в системе исследовалось при температуре 500-2200 ℃ для отдельных составов с шестью включениями 8-10-12-14-16-18 кг и давлением 0,1 МПа. С помощью системы Mn-Si-Al-Ca-Mg-OC изучен механизм совместного карботермического восстановления марганца, кремния, воздействия, электричества и железа. Проведенные расчеты позволяют полностью учесть все физико-химические процессы, протекающие при выплавке стандартного ферросиликомарганца карботермическим методом. В ходе анализа установлено, что производство металлической фазы стандартного ферросиликомарганца соответствует ГОСТ 4756-91 при температуре 1600-1700 ℃ с нагрузкой 12-14 кг на 100 кг шихты. При дальнейшем повышении температуры марганец и кремний начинают переходить в газовую фазу. Химический состав сплава при 1700 ℃ с добавкой 12 кг, %: Mn – 73,05; Си – 16,24; Fe – 9,67 и C – 1,03, а при содержании 14 кг составляет, %: Mn – 73,15; Си – 17,12; Fe – 8,24 и C – 1,48. Термодинамическое моделирование фазовых переходов подсистемы марганцевая шихта – восстановитель ферросиликомарганца из трудноизвлекаемых окисленных марганцевых руд Жайремского месторождения и марганцевых шлаков методом электроплавки.

CORROSION EVALUATION OF LPBF-MANUFACTURED DUPLEX STAINLESS STEEL

Zbigniew Brytan — 2024-03-25

In this study, the effect of as built and heat-treated additively manufactured 2507 super duplex stainless steel (SDSS) on electrochemical corrosion performance was examined. The corrosion was studied by Tafel polarization and electrochemical impedance spectroscopy (EIS) methods in a 3.5% NaCl solution. For this purpose, the as-built and heat-treated printed samples (solution annealed and stress-relieved) were examined by LOM/SEM and X-ray diffraction to evaluate the phase changes of steel at different processing stages. The correlation between corrosion resistance, structure, and heat treatment was assessed. As a result of the very fast cooling rate of the LPBF process, SDSS reveals ferrite as the major phase in the printed samples. To enhance the corrosion resistance of LPBF-produced duplex stainless steel, it's crucial to balance its two-phase structure and minimize residual stresses. The ferrite grains are elongated in the build direction, with some austenite precipitation along the grain boundaries or as Widmanstatten laths. The stress-relieved and as-printed SDSS exhibits reduced corrosion characteristics by around 20% compared to the solution-annealed SDSS, according to anodic polarization curves. Based on EIS results, the solution-annealed SDSS revealed an almost double increase in corrosion resistance (based on charge transfer resistance values) compared to the as-printed and stress-relieved conditions.

NUMERICAL SIMULATION OF BENDING STEELS USED IN AUTOMOTIVE INDUSTRY WITH EMPHASIS ON SPRINGBACK

Mulidrán — 2024-03-25

In this work, the influence of material models used in the FE simulation on the springback prediction of various steels is investigated. The aim of this work is to extend the knowledge base regarding springback prediction of steels used in car production. The springback effect after V-bending operation was studied on TRIP, HSLA and EDDQ steels. The bending angle was set to 90°. In the numerical simulation, Hill48 and Barlat yield criteria were used in combination with Ludwik's and Swift's hardening models. Achieved data from the numerical simulations were compared and evaluated with experimental test results. The experimental results showed the relation between springback and mechanical properties, mainly the yield strength. Higher values of yield strength have negative impact on the final angle of the bent part, thus increasing springback of the part. The numerical results of the springback were not identical with the experimentally achieved springback values in most cases. Particularly, when Swift yield criterion was used in the simulation.