This paper analyses the effect of different charge compositions for melt production, cooling rate (i.e. casting wall thickness) and inoculation on the gray iron microstructure. In this study, three gray iron melts were produced that had almost the same chemical composition. The proportions of steel scrap (SS), pig iron (PI), gray iron return (GIR) and SiC in charge were as follows: melt 1 (10 % SS, 39.4 % PI, 49.2 % GIR, 0.6 % SiC), melt 2 (38.8 % SS, 9.9 % PI, 47.9 % GIR, 1.6 % SiC) and melt 3 (0 % SS, 0 % PI, 99.2 % GIR, 0.06 % SiC). One uninoculated and one inoculated stepped test casting with walls thicknesses of 5, 10, 20, 45 and 65 mm was casted from each melt. The inoculant was added in the melt stream during pouring in the mould in an amount of 0.23 wt.%. The type, size and distribution of graphite flakes in the analysed walls did not significantly depend on the charge compositions. The structure of the metal matrix, carbides precipitation and type, size and distribution of graphite flakes were largely dependent on the wall thickness. As the wall thickness increased, the cooling rate decreased and the type of graphite flakes changed, from D and E through B to A type. Carbide formation has occurred in the edge region of the 5 mm thick walls. With the decrease of the cooling rate and increasing the proportion of D and E type graphite flakes, the ferrite content in the metal matrix increased. The carbide content in the edge region of the 5 mm thick walls was significantly reduced by inoculation. Inoculation increased the proportion of A type graphite flakes in the middle of 5 mm thick wall and in walls with a thickness from 10 to 65 mm. In addition, inoculation significantly reduced the proportion of B, D and E type graphite flakes or were completely eliminated. Wall thickness has affected this effect.
Materials Science. Non-Equilibrium Phase Transformations.
Vol. 8 (2022), Issue 1
Table of Contents
The features of recrystallization of steels with different chemical composition and type of crystal lattice under laser action were investigated. These processes are of great importance in high-speed laser heating and cooling, as well as in the formation of the microstructure of steels under the influence of residual heat.
It was found that recrystallization under laser action has signs of a dynamic process due to an increase in the dislocation density. In addition, the dislocation substructure of steel is inherited from the initial hot-deformed state. It is shown that the mechanism of laser recrystallization depends on the type of steel, chemical composition, and crystal lattice.
In different steels, the development of primary, collective, and secondary recrystallization was observed. In this case, the change in the grain structure of steels took place against the background of an increased density of dislocations and the formation of a cellular dislocation substructure.
The properties of an array of carbon nanostructures or a material containing its is differ from the properties of individual components. For bulk array of carbon nanostructures it is unknown to what extent the electrons of each layer participate in conductivity, the role of defects is not defined. properties. So, this work presents some answers to these questions.
Research on vegetable oils was already carried out in the industrial era. Oils are used not only in the food industry, but also in the cosmetics and pharmaceutical industries. Due to the beneficial effect on the human body, they have been studied more and more thoroughly. The development of high pressure food preservation has further accelerated this process. Due to the use of pressure in the production and preservation of food, it turned out to be important to study the phase transitions induced by pressure in these oils. Due to their long-term nature, these transformations may damage the machines used in the industry. So far well-researched vegetable oils in this regard are castor oil, rapeseed oil, soybean oil, sunflower oil and olive oil. Research on other oils will be conducted in the future.
The Electrothermal Processes During High-voltage Electric Pulse Consolidation of Refractory Powder Materialspg(s) 16-18
The main features of high-voltage electric pulse consolidation (HVC) of refractory powder materials and the resulting unique capabilities of the method are considered. The electro-thermal processes of HVC at the contacts between powder particles and at the macroscale of the entire consolidated sample are analyzed. The results of experimental studies of the parameters of high-voltage electrical impulse action in the processes of consolidation of high-temperature powder compositions, high-voltage welding of dissimilar materials, as well as high-voltage discharges in liquid are presented. The results of measuring the intensity of thermal radiation of the investigated materials under high-voltage electrical impulse action, recorded by the method of pulse photometry using photodiode sensors, which, together with the Rogowski coil, are components of the measuring complex developed by the authors, are presented.
The reactive ball milling technique was applied to fabricate the Mg-based composite with graphite additives. The sorption/desorption kinetics of the composites were investigated under isothermal conditions. The best hydrogen sorption/desorption kinetics was attained for the magnesium-carbon composite synthesized using the low surface area graphite powder as an active additive. This sample is characterised by the best kinetics performance compared to other composites. It releases 4.2 wt.% of hydrogen at 270 ºC within ~18 min and uptakes 4.6 wt/.% of hydrogen for ~130 min at 200 ºC.
The results of testing a nozzle with a zero angle of attack for obtaining atomized metal powders are presented, which indicate its increased overhaul life, a satisfactory yield of fine fraction powders with a good spherical powder shape.
Nanotechnology has grown in popularity due to the enormous potential for producing materials and products with diverse properties, allowing significant advancement of existing technology and the development of new innovative technologies. Nanomaterials behave differently at the nanoscale than their conventional counterparts, opening exciting new possibilities in a wide range of construction applications. Nonetheless, the lack of information on nanomaterials’ suitability, high costs, and health risks limits their use in construction and structural engineering. As a result, research must be conducted to provide accurate information and facts about the properties and performance of nanomaterials under various load conditions, as well as information on the advantages of using nanomaterials over other construction materials. This paper provides information on nanomaterial properties and how they affect structural materials’ microstructure and mechanical properties. It also demonstrates the benefits of using nanotechnology and suggests new possibilities.