Introduction of polymers into the cement composites improves same of the properties of concretes and mortars. Therefore, the polymer-cement composites are successfully used in construction. The model of microstructure formation in cement composites modified with thermoplastic polymer (pre-mix modifiers) has already been developed and successfully implemented. However, the formation of microstructure in the case of epoxy-cement composites (containing post-mix modifier) demonstrates same peculiarities which should be taken into account when modelling the process. The microstructure of epoxy-cement composites and its formation is discussed in the paper. The model is offered, formulated on the basis of the microscopic observations and results of testing.
The thermochemical treatment applied to improve the surface properties of AZ91 consisted in heating the material in contact with AlSi10Mg powder at 445 oC for 30 min. During heat treatment process the powder was held under pressure to facilitate the diffusion of the alloying elements to the substrate and, accordingly, the formation of a modified layer. Two pressures, 1 MPa and 5 MPa, were tested. The resultant layers, containing hard Mg2Si and Mg17Al12 phases, were examined using an optical microscope and a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (EDS). The experimental data show that the layer microstructure was dependent on the pressure applied. A thicker, three-zone layer (about 200 μm) was obtained at 1 MPa. At the top, there were Mg2Si phase particles distributed over the Mg17Al12 intermetallic phase matrix. The next zone was a eutectic (Mg17Al12 and a solid solution of Al in Mg) with Mg2Si phase particles embedded in it. Finally, the area closest to the AZ91 substrate was a eutectic not including the Mg2Si phase particles. By contrast, the layer produced at a pressure of 5 MPa had lower thickness of approx. 150 μm and a two-zone structure. Mg2Si phase particles were present in both zones. In the upper zone, Mg2Si phase particles were regularly distributed over the Mg17Al12 intermetallic phase matrix. The lower zone, adjacent to the AZ91, was characterized by a higher volume fraction of Mg2Si phase particles distributed over the matrix composed mainly of Mg17Al12. The alloyed layers enriched with Al and Si had much higher hardness than the AZ91 substrate.
Metallic bearing alloys have different types, most of which are tin (Babbitt) or bronze based. Bronze bearings are used at heavy duty conditions. The goal of this research is an investigation on the effect of cooling rate and pouring temperature (two important factors in casting production) on the Brinell hardness and pin-on-disc wear resistance (two important properties in bearing applications) of bronze SAE660. The melt had prepared by induction furnace. Then, it had poured in sand mold in four different casting conditions, including pouring temperatures of 950 oC and 1200 oC, and cooling with water and air. Finally, the microstructure, hardness and wear resistance of the SAE660 had investigated. The results indicated that if the maximum hardness, along with the minimum weight loss due to wear (or maximum wear resistance) is required; the contents of intermetallic compounds, lead phase and the solid solution phase should be more. In this way, the samples which are cooled in air and poured at 950 oC have the high hardness and the lowest weight loss.
A method of using the electric charge in a capacitor was applied for the manufacture of thermocouple micro-joints. The motivation for the study was the need to produce a stable welded connection without affecting the geometry of the substrate, which was a thin sheet of Inconel 625 alloy (UNS designation N06625). Within the framework of the research work, a suitable workstation for micro-joints elaboration was built and welding experiments were performed using different electric charges. Studies carried out within the framework of the present work have shown that joints based on Inconel 625 alloy and platinum have the best application properties in the range of small-scale temperature measurements. They can be used, e.g., for monitoring the temperature distribution on the inner surfaces of electric motor casings. An undeniable advantage is in this case the high thermal resistance of both materials used to produce the joint, i.e. the Inconel 625 alloy and platinum. This allows them to be used at high temperatures under atmospheric conditions.
This paper presents the results of studies of high-alloyed white cast iron modified with lanthanum, titanium, and aluminium-strontium. The samples were taken from four melts of high-vanadium cast iron with constant carbon and vanadium content and near-eutectic microstructure into which the tested inoculants were introduced in an amount of 1 wt% respective of the charge weight. The study included a metallographic examinations, mechanical testing, as well as hardness and impact resistance measurements taken on the obtained alloys. Studies have shown that different additives affect both the microstructure and mechanical properties of high-vanadium cast iron.
The multiple direct remelting of composites based on the A359 alloy reinforced with 20% of Al2O3 particles was performed. The results of both gravity casting and squeeze casting were examined in terms of the obtained microstructure and mechanical characteristics. In microstructure examinations, the combinatorial method based on phase quanta theory was used. In mechanical tests, the modified low cycle fatigue method (MLCF) was applied. The effects obtained after both gravity casting and squeeze casting were compared. It was noted that both characteristics were gradually deteriorating up to the tenth remelting. The main cause was the occurrence of shrinkage porosity after the gravity casting. Much better results were obtained applying the squeeze casting process. The results of microstructure examinations and fatigue tests enabled drawing the conclusion that the A359 alloy reinforced with Al2O3 particles can confer a much better fatigue life behavior to the resulting composite than the A359 alloy without the reinforcement. At the same time, comparing these results with the results of the previous own research carried out on the composites based also on the A359 alloy but reinforced in the whole volume with SiC particles, it has been concluded that both types of the composites can be subjected to multiple remelting without any significant deterioration of the structural and mechanical characteristics. The concepts and advantages of using the combinatorial and MLCF methods in materials research were also presented
High-tin bronzes are used for church bells and concert bells (carillons). Therefore, beside their decorative value, they should also offer other functional properties, including their permanence and good quality of sound. The latter is highly influenced by the structure of bell material, i.e. mostly by the presence of internal porosity which interferes with vibration of the bell waist and rim, and therefore should be eliminated. The presented investigations concerning the influence of tin content ranging from 20 to 24 wt% on mechanical properties of high-tin bronzes allowed to prove the increase in hardness of these alloys with simultaneous decrease in the tensile and the impact strengths (Rm and KV, respectively) for the increased tin content. Fractures of examined specimens, their porosity and microstructures were also assessed to explain the observed regularities. A reason of the change in the values of mechanical properties was revealed to be the change in the shape of α-phase crystals from dendritic to acicular one, and generation of grain structure related to the increased Sn content in the alloy.
This work presents an influence of cooling rate on crystallization process, structure and mechanical properties of MCMgAl12Zn1 cast magnesium alloy. The experiments were performed using the novel Universal Metallurgical Simulator and Analyzer Platform. The apparatus enabled recording the temperature during refrigerate magnesium alloy with three different cooling rates, i.e. 0.6, 1.2 and 2.4°C/s and calculate a first derivative. Based on first derivative results, nucleation temperature, beginning of nucleation of eutectic and solidus temperature were described. It was fund that the formation temperatures of various thermal parameters, mechanical properties (hardness and ultimate compressive strength) and grain size are shifting with an increasing cooling rate.
Ultrasonic pulse echo technique was used to study cupric oxide (CuO) thin films. CuO thin films were prepared using sol gel technique. They were doped with Lithium (Li) (1%, 2% and 4%). Thin films’ thickness (d) and band gap energy (Eg) were measured. In addition, elastic moduli (longitudinal (L), shear (G), bulk (K) and Young’s (E)) and Poisson’s ratio (v) were determined to estimate the microstructure properties of the prepared films. The study ameliorated the used transducers to overcome their dead zone and beam scattering; wedges were developed. The results showed the effectiveness of these wedges. They enhanced transducers’ sensitivity by changing the dead zone, beam diameter, beam directivity and waves’ transmission. Also, the study noted that Li doping caused the improvement of CuO thin films to be more useful in solar cell fabrication. Li-CuO thin films had narrower band gap. Thus, they acquired a high quantum yield for the excited carriers; also they gained more efficiency to absorb solar light.
Hybryd PLD method was used for deposition high quality thin Ti, TiN, Ti(C,N) and DLC coatings. The kinetic energy of the evaporated particles was controlled by application of variation of di#11;erent reactive and non reactive atmospheres during deposition. The purpose was to improve adhesion by building a bridge between the real ceramic coating and the substrate. A new layer composition layout was proposed by application of a bu#11;er, starting layer. Advanced HRTEM investigation based on high resolution transmission electron microscopy was used to reveal structure dependence on specific atmosphere in the reactive chamber. New experimental technique to examine the crystallographic orientation based on X-ray texture tomography was applied to estimate contribution of the atmosphere to crystal orientation. Using Dictyostelium discoideum cells as a model organism for specific and nonspecific adhesion, kinetics of shear flow-induced cell detachment was studied. For a given cell, detachment occurs for critical stress values caused by the applied hydrodynamic pressure above a threshold. Cells are then removed from the substrate with an apparent first-order rate reaction that strongly depends on the stress. The threshold stress depends on cell size and physicochemical properties of the substrate, but it is not a#11;ected by depolymerization of the actin and tubulin cytoskeleton.
The paper describes the studies of ternary SnZn9Al1.5 lead-free alloy from the viewpoint of its mechanical behavior as well as microstructure examined by the light and scanning electron microscopy. The authors focused their attention specifically on the fatigue parameters determined by the original modified low-cycle fatigue method (MLCF), which in a quick and economically justified way allows determination of a number of mechanical parameters based on the measurement data coming from one test sample only. The effect of the addition of 1.5% Al to the binary eutectic SnZn9 alloy on its microstructure and the obtained level of mechanical parameters was analyzed. The phases and intermetallic compounds occurring in the alloy were identified based on the chemical analysis carried out in micro-areas by the SEM/EDS technique. It was shown that the addition of 1.5% Al to the binary eutectic SnZn9 alloy resulted in a more favorable microstructure and consequently had a positive effect on the mechanical parameters of the alloy. Based on the conducted research, it was recommended to use a combinatorial method based on the phase quanta theory to quickly evaluate the microstructure and the original MLCF method to determine a number of mechanical parameters.
Lead-free alloys containing various amounts of zinc (4.5%, 9%, 13%) and constant copper addition (1%) were discussed. The results of microstructure examinations carried out by light microscopy (qualitative and quantitative) and by SEM were presented. In the light microscopy, a combinatorial method was used for the quantitative evaluation of microstructure. In general, this method is based on the phase quanta theory according to which every microstructure can be treated as an arrangement of phases/structural components in the matrix material. Based on this method, selected geometrical parameters of the alloy microstructure were determined. SEM examinations were based on chemical analyses carried out in microregions by EDS technique. The aim of the analyses was to identify the intermetallic phases/compounds occurring in the examined alloys. In fatigue testing, a modified low cycle fatigue test method (MLCF) was used. Its undeniable advantage is the fact that each time, using one sample only, several mechanical parameters can be estimated. As a result of structure examinations, the effect of alloying elements on the formation of intermetallic phases and compounds identified in the examined lead-free alloys was determined. In turn, the results of mechanical tests showed the effect of intermetallic phases identified in the examined alloys on their fatigue life. Some concepts and advantages of the use of the combinatorial and MLCF methods in materials research were also presented.
The results of studies presented in this article are an example of the research activity of the authors related to lead-free alloys. The studies covered binary SnZn90 and SnZn95 lead-free alloys, including their microstructure and complex mechanical characteristics. The microstructure was examined by both light microscopy (LM) and scanning electron microscopy (SEM). The identification of alloy chemical composition in micro-areas was performed by SEM/EDS method. As regards light microscopy, the assessment was of both qualitative and quantitative character. The determination of the geometrical parameters of microstructure was based on an original combinatorial method using phase quantum theory. Comprehensive characterization of mechanical behavior with a focus on fatigue life of alloys was performed by means of the original modified low cycle fatigue method (MLCF) adapted to the actually available test machine. The article discusses the fatigue life of binary SnZn90 and SnZn95 alloys in terms of their microstructure. Additionally, the benefits resulting from the use of the combinatorial method in microstructure examinations and MLCF test in the quick estimation of several mechanical parameters have been underlined.
The study includes the results of research conducted on selected lead-free binary solder alloys designed for operation at high temperatures. The results of qualitative and quantitative metallographic examinations of SnZn alloys with various Zn content are presented. The quantitative microstructure analysis was carried out using a combinatorial method based on phase quanta theory, per which any microstructure can be treated as an array of elements disposed in the matrix material. Fatigue tests were also performed using the capabilities of a modified version of the LCF method hereinafter referred to in short as MLCF, which is particularly useful in the estimation of mechanical parameters when there are difficulties in obtaining many samples normally required for the LCF test. The fatigue life of alloys was analyzed in the context of their microstructure. It has been shown that the mechanical properties are improved with the Zn content increasing in the alloy. However, the best properties were obtained in the alloy with a chemical composition close to the eutectic system, when the Zn-rich precipitates showed the most preferred morphological characteristics. At higher content of Zn, a strong structural notch was formed in the alloy because of the formation in the microstructure of a large amount of the needle-like Zn-rich precipitates deteriorating the mechanical characteristics. Thus, the results obtained during previous own studies, which in the field of mechanical testing were based on static tensile test only, have been confirmed. It is interesting to note that during fatigue testing, both significant strengthening and weakening of the examined material can be expected. The results of fatigue tests performed on SnZn alloys have proved that in this case the material was softened.
The article presents the study results of Sn-Zn lead-free solders with the various Zn content. The results concern the hypoeutectic, eutectic and hypereutectic alloys containing respectively 4.5% Zn, 9% Zn and 13.5% Zn. Moreover, these alloys contain the constant Ag (1%) addition. The aim of the study was to determine the microstructural conditionings of their fatigue life. In particular it was focused on answer the question what meaning can be assigned to the Ag addition in the chemical composition of binary Sn-Zn alloys. The research includes a qualitative and quantitative assessments of the alloy microstructures, that have been carried out in the field of light microscopy (LM). In order to determine some geometrical parameters of the microstructure of alloys the combinatorial method based on the phase quanta theory was applied. Moreover, for the identification necessities the chemical analyses in the micro-areas by SEM/EDS technics were also performed. Based on the SEM/EDS results the phases and intermetallic compounds existing in the examined lead-free solders were identified. The mechanical characteristics were determined by means of the modified low cycle test (MLCF). Based on this method and on the results obtained every time from only one sample the dozen of essential mechanical parameters were evaluated. The research results were the basis of analyzes concerning the effects of microstructural geometrical parameters of lead-free alloys studied on their fatigue life at ambient temperature.
Using methods of physical material studies (scanning electron microscopy and micro X-ray spectral analysis), a study was carried out with focus on alteration of structure and phase composition in surface layers of Al-Si alloy (silumin АК10М2N) treated in electroexplosive alloying with a multiphase plasma jet formed in the process of aluminum foil explosion and carrying particles of Y2O3 weighted powder portion. It was revealed that a porous surface layer with non-homogeneously distributed alloying elements (silicon, yttrium) in it is formed in any conditions of electroexplosive alloying of silumin. Thickness of the modified layer is different, varying 50 to 160 µm, depending on the zone to be examined. The modified surface consists basically of Al, Si and Y. Yttrium in the modified layer is thought to be an indirect evidence of better physical and mechanical properties of the surface layer in comparison with the base material.
This research work is focused on examining the turning behavior of Incoloy 800H superalloy by varying important cutting parameters. Incoloy 800H is an Iron- Nickel-Chromium based superalloy; it can withstand high temperature (810°C), high oxidization and corrosion resistance. But, it is difficult to turn in conventional machines and hence the present work was carried out and investigated. Experiments were conducted based on the standard L27 orthogonal array using uncoated tungsten inserts. The cutting force components, namely, feed force (Fx), thrust force (Fy) and cutting force (Fz); surface roughness (Ra) and specific cutting pressure (SCPR) were measured as responses and optimized using Taguchi-Grey approach. The main effects plots and analysis of mean (ANOM) were performed to check the effect of turning parameters and their significance on responses of cutting forces in all the direction (FX, FY, FZ), the surface roughness (Ra) and specific cutting pressure (SCPR). The tool wear and machined surfaces were also investigated using white light interferometer and SEM.
Characteristics of the microstructure of corrosion-resistant cast 24Cr-5Ni-2.5Mo duplex steel after introduction of 0.98, 1.67 and 4.3% Si were described. Based on the test results it has been found that silicon addition introduced to the corrosion-resistant cast two-phase duplex steel significantly reduces austenite content in the alloy matrix. Increasing silicon content in the test alloy to 4.3% has resulted, in addition to the elimination of austenite, also in the precipitation of Si-containing intermetallic phases at the grain boundaries and inside the grains. The precipitates were characterized by varying content of Cr and Mo, indicating the presence in the structure of more than one type of the brittle phase characteristic for this group of materials. The simulation using Thermo-Calc software has confirmed the presence of ferrite in all tested alloys. In the material containing 4.3% Si, the Cr and Si enriched precipitates, such as G phase and Cr3Si were additionally observed to occur.
In Poland, researchers have a very strong interest in archaeometallurgy, which, as presented in classical works, focuses on dating artefacts from the prehistoric and early medieval periods in the form of cast iron and copper castings. This study, extending the current knowledge, presents the results of a microstructure investigation into the findings from the Modern era dating back to the late Middle Ages. The investigated material was an object in the form of a heavy solid copper block weighing several kilograms that was excavated by a team of Polish archaeologists working under the direction of Ms Iwona Młodkowska-Przepiórowska during works on the marketplace in the city of Czestochowa during the summer of 2009. Pre-dating of the material indicates the period of the seventeenth century AD. The solid copper block was delivered in the form of a part shaped like a bell, named later in this work as a “kettlebell”. To determine the microstructure, the structural components, chemical composition, and homogeneity, as well as additives and impurities, investigations were carried out using light microscopy, scanning electron microscopy including analysis of the chemical composition performed in micro-areas, and qualitative X-ray phase analysis in order to investigate the phase composition. Interpretation of the analytical results of the material’s microstructure will also help modify and/or develop new methodological assumptions to investigate further archaeometallurgical exhibits, throwing new light on and expanding the area of knowledge of the use and processing of seventeenth-century metallic materials.
The results of structure and mechanical properties investigations of tungsten heavy alloy (THA) after cyclic sintering are presented. The material for study was prepared using liquid phase sintering of mixed and compacted powders in hydrogen atmosphere. The specimens in shape of rods were subjected to different number of sintering cycles according to the heating schemes given in the main part of the paper From the specimens the samples for mechanical testing and structure investigations were prepared. It follows from the results of the mechanical studies, that increasing of sintering cycles lead to decrease of tensile strength and elongation of THA with either small or no influence on yield strength. In opposite to that, the microstructure observations showed that the size of tungsten grain increases with number of sintering cycles. Moreover, scanning electron microscope (SEM) observations revealed distinctly more trans-granular cleavage mode of fracture in specimens subjected to large number of sintering cycles compared with that after one or two cycles only.
Currently is the biggest problem of metallurgical companies the increase of fossil fuel prices and strict environmental regulations. As a result of this, companies must look for alternatives that would reduce the amount of fossil fuels and reduce emissions. Wood sawdust has huge energy potential, which can be used in the process of agglomerate production. This type of energy is locally available, has some similar properties as fossil fuels and is economically advantageous. For these reasons, experimental study using laboratory agglomeration pan was realized to study the possibility of agglomerate production with a mixed fuel. Experimental results show the viability of mixed fuel use in the agglomeration process, but also show significant possibility for improvement. The maximum acceptable substitution ratio, which corresponds to qualitatively suitable agglomerate is 20% of pine sawdust. Based on the realized experiments and the obtained results we have acceded to the intensification of the agglomeration process with an objective to increase the amount of added substitution fuel while maintaining the required quality of agglomerate.
Mechanical properties and residual stresses of friction stir welded and autogenous tungsten inert gas welded structural steel butt welds have been studied. Friction stir welding (FSW) of structural steel butt joints has been carried out by in-house prepared tungsten carbide tool with 20 mm/ min welding speed and 931 rpm tool rotation. Tungsten inert gas (TIG) welding of the butt joints was carried out with welding current, arc voltage and the welding speed of 140 amp, 12 V and 90 mm/min respectively. Residual stress measurement in the butt welds has been carried out in weld fusion zone and heat affected zone (HAZ) by using blind hole drilling method. The magnitude of longitudinal residual stress along the weld line of TIG welded joints were observed to be higher than friction stir welded joint. In both TIG and FSW joints, the nature of longitudinal stress in the base metal was observed to be compressive whereas in HAZ was observed to be tensile. It can be stated that butt welds produced with FSW process had residual stress much lower than the autogenous TIG welds.