Papers by Keyword: Quantitative Metallography

Abstract: In the phase transformations of the solid state, situations can occur in which the initial phase transform forming two or more distinct phases. The exact mathematical model for situations where more than one transformation occurs simultaneously or sequentially was proposed by Rios and Villa. The computational simulation was used to study the evolution and visualization of the possible microstructures that these transformations may present. The causal cone methodology was adopted. The simulations were compared with the analytical model to ensure that they occur as expected. The growth of individual grains of each phase was monitored in 3D microstructure evolution. With this monitoring, was possible to extract useful data able to quantify the simulated 3D microstructure. Quantifying the simulated microstructures increase the possibility of the simulations give to the experimentalist insights about the transformations. In this paper, it is verified that each grain evolves in an individual way, as expected, however their growth is similar.

Abstract: The electrode processes are often studied on iron for the needs of hydrogen technologies. This paper presents the use of the resources of the “MicroScan” program in manual methods to determine the stereological parameters of the Armco iron. For this purpose, the average number of particles per one unit of the N_A surface area and the average surface area of the grains in the 〈A flat structure were determined, using the planimetric, the Jeffries and the comparative methods. The linear method was used to determine the average number of segments per one length unit of the N_L structure and the average length of the circuits of grains in the 〈L flat structure. It was found out that the mean values of the determined parameters were in line with the PN-84/H-04507 standard and small differences existing in the obtained results were due to the jumping character of the pattern scale of the mentioned standard. The relative error of the N_A and A parameters indicates that the planimetric method allows to achieve the most accurate measurement of the size of the grain.

Abstract: Non-metallic inclusions may be introduced to liquid steel from the outside, usually with charge material, or they may be produced in the metallurgical process. According to literature, if evenly distributed, non-metallic inclusions may affect the functional properties of steel, mainly its fatigue strength. The aim of this study was to determine the quantity and dimensional structure of non-metallic inclusions in high-grade medium carbon steel melted in an electric furnace and subjected to desulfurization. The experimental material consisted of semi-finished products of high-grade, medium-carbon constructional steel containing manganese, chromium, nickel, molybdenum, and boron. The levels of phosphorus and sulphur impurities did not exceed 0.02%. Billet samples were collected to determine the chemical composition, microstructure, the relative volume of non-metallic inclusions, and the size of impurities. The results were processed and presented in graphic form.

Abstract: The subject matter of the paper is the quantitative evaluation of gaseous and shrinkage porosity in the turbine blades using quantitative metallography methods. The research material consisted of blades with a polycrystalline structure made of IN 713C superalloys. Three different shell mould systems were used during the investment casting: shell A - typical industrial shell mould system and used in this work as the reference; shell B – similar to version A, but SiC grit was applied as back-up stucco; shell C – entirely SiC shell mould system. The blades of superalloy IN-713C cast into the wholly SiC shell mould system have revealed much lower porosity as compared to the blades cast into the typical industrial shell mould system.

Abstract: The casting defects, microstructure and hardness of Elektron 21 Mg sand casting alloy was investigated. Visual and radiographic examination showed the presence of non-metallic inclusions and porosity. Quantitative analysis of microstructure was performed, no correlation between section thickness, grain size, volume fraction of eutectic areas and hardness was observed. Casting defects were responsible for cracking at magnesium casting/steel tube interface.

Abstract: In this paper the results of microstructural investigations and methodology of detection of intermetallic compounds were reported. The microstructural investigations included the light microscopy, scanning electron microscopy, chemical microanalysis and X-ray diffraction analysis. It was found that the microstructure of Mg-5Al-3Ca-0.7Sr-0.2Mn alloy consists of α-Mg, (Mg,Al)2Ca, Al3Mg13(Sr,Ca), Mg2Ca and Al2Ca intermetallic phases. The correct detection of these phases requires the high magnifications and a large number of measurements fields.

Abstract: The subject matter of the paper is the quantitative evaluation of gaseous and shrinkage porosity in construction elements of a low-pressure aircraft engine turbine using quantitative metallography methods. The research material comprised blades and blade segments with a polycrystalline structure made of IN 713C and MAR M247 superalloys. One of the major problems that occur in the precision castings is their porosity: gaseous, which is the result of emission of dissolved gases from the superalloy during solidification, and shrinkage, being the result of shrinkage of the superalloy and of insufficient feeding of the interdendritic space. The developed practical procedure of selective measurement of gaseous and shrinkage porosity enabling the examination of precision castings made of high-temperature creep resisting nickel superalloys is presented.

Abstract: In the course of our experiments we have developed an etching process by means of which the austenite grains formed subsequent to roughing can be made visible in the case of Grade X80Mo0 and X80Mo2 microalloyed steels. The definition of the size and elongation of the grains enables the production process to be optimized and the microstructure features associated with the desired mechanical properties attained thereby.

Abstract: Magnesium alloys are the lightest, widely used structural material. They are often used in aeronautical and automotive industries, where the weight savings are essential. Magnesium alloys present acceptable mechanical properties but their high temperature properties are unsatisfactory. This led to development of magnesium alloys with rare earth elements addition. To achieve good mechanical properties these alloys are modified with zirconium. Modification affects positively also corrosion resistance of Mg-RE alloys. It is important to study impact of modifier amount on the structure and properties of these alloys. Unmodified and modified alloys were investigated. Three variants of modification were: modification according to Magnesium-Elektron specification, 50% and 100% more modifier. Mechanical and structural properties were investigated. Fractures were observed on scanning electron microscope. Results showed that grain refinement and yield strength increase with increasing amount of modifier. Impact of modification on tensile strength is unclear, probably because of non-metallic inclusions in the material’s structure. The inclusions sources are oxygenated nappe of liquid metal and fluxes, used during smelting.

Abstract: Magnesium alloys, thanks to their low density, are characterized by very high specific strength and specific stiffness. Due to acceptable mechanical properties, these alloys are widely used in automotive and aerospace industries for the elements such as: gearbox and engine housings, steering wheel columns or wheels. The main problem of the most common magnesium alloys – such as AZ91 are their weak high temperature properties. This led to development of alloys containing rare earth elements. These alloys achieve their demanded mechanical properties after grain refinement with the zirconium. Because of a big responsibility of the elements made from Mg-RE alloys, it is important to investigate modification impact on properties of the magnesium alloys. The paper presents results of studies properties of the WE43 and Elektron 21 casting magnesium alloys, modified in three different ways – according to Magnesium-Elektron specification, 50% stronger modification and 100% stronger. For the comparison, unmodified alloys were also investigated. Investigations showed, that alloys modified according to MEL specification presents optimal set of structural and mechanical properties. Further increase of amount of modifiers doesn’t let to significant increase of mechanical properties. Fractographic investigations showed many non-metallic inclusions on the fractures surface, which are result of faulty smelting process.