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Evaluation of cracking risk of 80MnSi8-6 nanobainitic steel during hot forging in the range of lower temperature limits

Lisiecka-Graca Paulina, Lisiecki Łukasz, Zyguła Krystian, Wojtaszek Marek

Materials Science Poland

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2024

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Vol. 42, No. 1

171--185

EN

Nanobainitic steels exhibit an exceptional combination of high strength, good plasticity, impact toughness, and wear resistance. They are suitable for the production of large mass components through the open-die forging process. Subsequently, the forgings are air-cooled. An obstacle of this method is the extended time required for the large forgings to undergo a bainitic transformation, making the industrial implementation of this process economically unjustifiable. Nevertheless, nanobainitic steels also allow for the open-die forging of small batches of structural elements with high property requirements. A technological limitation lies in the necessity of performing a series of operations, leading to a prolonged processing time dependent on the shape of the product and the degree of deformation. Therefore, inter-operational reheating is often necessary, incurring costs and time consumption. This is particularly relevant to forgings with a mass ranging from a few to several dozen kilograms, which, due to their low thermal capacity, rapidly dissipate heat to the surroundings and tools. Designing an economical process with a limited number of reheating cycles requires advanced knowledge of material behavior under thermo-mechanical deformation parameters, including boundary conditions where a significant decrease in plasticity occurs and the risk of crack initiation. To obtain this information, a comprehensive analysis of the influence of thermo-mechanical parameters applied during the deformation of nanobainitic steel at relatively low temperatures on the flow characteristics and crack formation was conducted. To achieve this goal, the Digital Image Correlation method, the finite element method modeling considering damage criteria, and the macrostructural evaluation of deformed specimens were employed.

2

The Application of Fuzzy Logic Analysis for the Fast Calculations of Proper Parameters of Manufacturing Titanium Alloys from Powders

Zyguła Krystian, Wojtaszek Marek

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

703--710

EN

This paper presents a method based on the use of fuzzy logic for the rapid selection of optimal induction sintering parameters. The prepared fuzzy controller uses expert knowledge developed from the results of induction sintering tests of Ti-5Al-5Mo-5V-3Cr alloy green compacts produced from a mixture of elemental powders. The analysis of the influence of the applied sintering parameters on the material characteristics was based on the evaluation of the microstructure state and the measurement of the relative density of the samples after sintering. In this way, a universal tool for estimating the sintering parameters of titanium powder-based green compacts was obtained. It was shown that with the help of fuzzy logic it is possible to analyze the influence of the parameters of the manufacturing process of metal powder materials on the quality of the obtained products.

3

Fast Estimation of Favorable Parameters of Hot Metal Forming, Using the Fuzzy Logic Method

Wojtaszek Marek, Zyguła Krystian

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

723--731

EN

The paper presents an approach based on the use of the fuzzy logic method as a tool for quick estimation of favorable parameters of hot plastic working of selected alloy and for the identification of those combinations of parameters that should be avoided. The idea and basic principles of operation of fuzzy controllers for the selection of thermo-mechanical parameters of hot metal forming were presented. The most important information necessary for a quick analysis based on knowledge engineering has been compiled. An example of the fuzzy controller using the information obtained based on plastometric test data and the results of observation of the microstructure state of deformed samples at various temperature and strain rate variants is presented. For the tested alloy, it was shown that the analysis of the parameters of their plastic processing using the fuzzy logic method, based on properly formulated expert knowledge, leads to obtaining satisfactory results. Thus, it was confirmed that fuzzy logic can be successfully used as a tool for quick estimation of correct or unfavorable thermal and mechanical combinations of hot forging processes.

4

Forging of PM Ti-6Al-4V alloy at the temperature above β-transus and high strain rate: modeling and trials in industrial conditions

Wojtaszek Marek, Zyguła Krystian, Łukaszek-Sołek Aneta, Jabłońska Magdalena, Stanik Rafał, Gude Maik

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e102, 2023

EN

The results of the forging process in open dies of the powder metallurgy (PM) Ti-6Al-4V alloy, carried out at the temperature above β-transus and at a high strain rate were presented. As an initial material for the research relatively cheap elemental powders were used. This approach gives a real chance for the implementation of the developed technologies. As the range of phase transition temperature in titanium alloys is influenced also by the technology of their production, the β-transus temperature was estimated for the PM Ti-6Al-4V alloy. Finite element method (FEM) numerical analysis of the forging process at the temperature of 1000 °C and high strain rate was performed. The results obtained by the FEM modeling were verified under industrial conditions. The forging trials were made at the temperature of 1000 °C on a screw press operating at a speed of 250 mm s-1. For comparison, the alloy was also studied in as-cast and hot-rolled conditions, which is widely used as a feedstock. The influence of the method of manufacturing feedstock on the microstructure and selected properties of the forgings was determined. This approach allowed for a qualitative assessment of the PM material. The forging process in open dies of two different feedstocks led to the production of forgings with a uniform and similar lamellar microstructure. Thus, it was shown that the heating conditions, the parameters of the forging process, and the method of cooling the product after forging have a decisive influence on the microstructure condition of the forgings shaped in the temperature range of the β phase.

5

Manufacturing and properties of al-al alloy bimetallic composites obtained from powders by hot extrusion

Wojtaszek Marek, Zyguła Krystian

Composites Theory and Practice

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2022

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R. 22, nr 4

211--218

EN

This paper presents the process of manufacturing bimetallic composites in the shell-core system. Al17Si5Fe3Cu1.1Mg0.6Zr alloy powder was used for the shell. Pure aluminum was used as the core of the composite, respectively, in the form of a cast and then rolled rod, and in the form of a semi finished product obtained from aluminum powder. The semi-finished powders were produced by means of the uniaxial hot pressing method. From the components prepared in this way, an extrusion chargé was made by machining in an alloy shell-core system. Permanent bonding of the components and forming the required shape of the composites was carried out using direct hot extrusion under isothermal conditions. It was confirmed that the application of powder metallurgy technology for the production of one or both component materials makes it possible to conduct the extrusion of the components with significantly different plasticity without violating the cohesion of the layers. This approach made it possible to produce layered composites with high-strength properties of the outer layer and with a ductile core. The microstructural state of the components was evaluated, focusing on the continuity of the transition zone between the components. Observations of the separation lines between the layers revealed that the zone between the components was continuous, which was found for both composites, regardless of the examined cross-section. On this basis, it was concluded that the direct hot extrusion process, carried out under the adopted parameters, made it possible to combine the components very well. Selected properties of the layered composites were also determined. It was shown that the proposed method, combining powder metallurgy and hot forming technologies, makes it possible to obtain a continuous connection of components and produce products with properties significantly differentiating in the core and shell zones. These properties can be controlled by appropriate selection of the components, as well as by the method of manufacturing the core. Potential applications of the studied materials include the manufacture of bimetallic components for operation in conditions where significantly different properties of the outer zone and the core are required.

6

Selected aspects of manufacturing structural elements from titanium alloys combining cost-effective powder metallurgy technology and metal forming processes

Zyguła Krystian, Wojtaszek Marek, Śleboda Tomasz, Lypchanskyi Oleksandr

Computer Methods in Materials Science

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2019

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Vol. 19, No. 3

122--130

EN

Titanium alloys are mainly used in the automotive, aviation, shipbuilding and military industries. Their main advantages are low specific gravity, resistance to cracking and corrosion, high strength as well as fatigue strength. The most important disadvantages of titanium alloys include low thermal conductivity, difficulties in their machining and high cost of manufacturing. For the latter reason, titanium alloys are primarily used for the manufacturing of highly responsible components, such as implants and aviation structures, while the remaining products are produced in limited series. In the appropriate conditions, many titanium alloys can be formed in hot working processes. At present, in the processes of manufacturing structural elements of titanium alloys, a semi-finished products obtained by the casting method are commonly used. However, more and more research is being carried out on the use of powder metallurgy based material in this field. This approach opens up the possibility of decreasing production costs. As initial material, the alloy powders or mixtures of elemental powders can be used. The properties of alloy powder products are usually high and stable, however, the cost of powder production is high. Obtaining product from titanium alloys based on a powders mixture is relatively simple and significantly cheaper. The disproportion of prices causes, that a great number of research projects realized in recent years in the field of implementation of powder metallurgy for manufacturing titanium-based products is directed towards the use of powder mixtures since this approach gives real chances for the successful implementation of cost effective titanium alloys processing technology.

PL

Stopy tytanu są stosowane głównie w przemyśle motoryzacyjnym, lotniczym, stoczniowym i wojskowym. Ich głównymi zaletami są niski ciężar właściwy, odporność na pękanie i korozję, wysoka wytrzymałość oraz wytrzymałość zmęczeniowa. Do wad stopów tytanu można zaliczyć niską przewodność cieplną, skomplikowaną obróbkę mechaniczną i wysokie koszty produkcji. Z tego ostatniego powodu stopy tytanu są stosowane przede wszystkim do produkcji wysoce odpowiedzialnych elementów konstrukcyjnych, takich jak implanty i struktury lotnicze, podczas gdy pozostałe produkty są wytwarzane w ograniczonym stopniu. Stosując odpowiednie parametry termomechaniczne, stopy tytanu mogą być z powodzeniem kształtowane na drodze przeróbki plastycznej na gorąco. Obecnie w procesach wytwarzania elementów konstrukcyjnych stopów tytanu powszechnie stosuje się półprodukty uzyskane metodą odlewania. Jednak w tej dziedzinie prowadzone są coraz więcej badań nad wykorzystaniem materiałów opartych na metalurgii proszków. Takie podejście otwiera możliwość obniżenia kosztów produkcji. Jako materiał wyjściowy można zastosować proszki stopowe lub mieszaniny proszków elementarnych. Wykorzystanie proszków stopowych zwykle zapewnia wysokie i stabilne własności, jednak koszt produkcji takiego proszku jest wysoki. Otrzymywanie produktów ze stopów tytanu na bazie mieszaniny proszków elementarnych jest stosunkowo proste i znacznie tańsze. Dysproporcja cen powoduje, że ogromna liczba projektów badawczych zrealizowanych w ostatnich latach w zakresie wdrażania metalurgii proszków do wytwarzania produktów na bazie tytanu jest ukierunkowana na stosowanie mieszaniny proszków elementarnych, ponieważ takie podejście daje realne szanse na pomyślne wdrożenie opisanej technologii przetwarzania stopów tytanu.