Structural Aspects of Remelting of the AZ91 Magnesium Alloy Surface Layer

In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam

Asbestos-cement panels - microstructural investigations of asbestos fibres

W pracy podjęto się analizy materiałoznawczej włókien azbestu występujących w płytach azbestowo-cementowych. Do zobrazowania mikrostruktury włókien wykorzystano mikroskopię optyczną i skaningową mikroskopię elektronową. W oparciu o badania mikrostrukturalne dokonano oceny zagrożeń dla życia i zdrowia człowieka, wynikających z eksploatacji eternitu. Badaniom mikrostrukturalnym poddano ponadto płyty azbestowo-cementowe po obróbce termicznej. Badania te miały na celu zobrazowanie ewentualnych zmian w strukturze płyty oraz występujących w nich włókien azbestu, jakie mogą wystąpić w wyniku oddziaływania wysokiej temperatury, w tym także otwartego ognia np. w trakcie pożaru. Naświetlono ponadto aktualną sytuację w zakresie eliminowania zagrożeń, wynikających z użytkowania wyrobów zawierających azbest i przedstawiono metody utylizacji tego typu wyrobów.In this study, the material science analysis of asbestos fibres present in asbestos-cement panels was undertaken. To illustrate the microstructure of asbestos fibres, both optical and scanning electron microscopy was used. Based on the microstructural analysis, the risk to human life and health resulting from the use of eternit was assessed. In addition, structural investigations were carried out for asbestos-cement panels, subjected to thermal treatment. These investigations were aimed at illustrating the possible changes in panel microstructure and the asbestos fibres present within, which can come about as the result of the effect of a high temperature, including from a naked flame, e.g. during a fire. In addition, the current situation in the removal of risk resulting from the use of products containing asbestos fibres was made clear and methods of recycling such products were presented

GTAW surface treatment of 7075 aluminum alloy

Microscopic examinations were performed by means of an Olympus GX41 light microscope and a JEOL JSM-6610LV scanning microscope. EDS examinations were carried out using an X-ray microanalyzer by Oxford Instruments

Surface modification of ZrO2-10 wt. % CaO plasma sprayed coating

Oxide ZrO2-CaO plasma-sprayed coatings were remelted using the modified gas tungsten arc welding (GTAW) method. The original two-burner set, generating a free independent arc, was used in the treatment. The samples were subjected to structural examination using light and scanning electron microscopes, and energy-dispersive X-ray microanalysis (EDX). A substantial heterogeneity of the plasma-sprayed coatings was found, observable with a laminar structure, significant porosity, and step change in the concentration of the elements. Significant changes in the structure were found after the remelting treatment. Both microscopic and EDX investigations showed that the treatment leads to a reduction in the heterogeneity of the chemical composition of the coating material and to a loss of structural characteristics typical for plasma-sprayed coatings

Data for: Making asbestos-cement products safe using heat treatment

A composite cement-asbestos samples were placed in a corundum crucible and heated for 1 hour in an electric furnace. After the heating process the samples were subjected to microstructural investigations using scanning electron microscopy. These tests were carried out using a JEOL JSM-6610LV microscope after covering the samples earlier with a conductive layer of gold. X-ray examinations were also carried out to identify the asbestos form and evaluate the phase changes caused by the thermal treatment. XRD tests were carried out using the powder method on a Philips X'Pert Pro diffractometer. The measurement step was 0.008° and count time -50 s. Phase identification was performed based on data from the ICDD PDF-4 database. In the case of the selected samples, spectroscopic tests in the mid-infrared range - 4000 - 400 cm-1 (MIR) were also carried out. These tests were performed using a Bruker 70V spectrometer. Spectroscopic samples were prepared in the form of KBr pellets. The measurements were made by the transmission technique, and spectra were recorded on the scale of absorbance at 256 scans and 4 cm-1 resolution. The chemical composition of the samples was determined using an Axios Max WD-XRF X-ray fluorescence spectrometer with wavelength dispersion using a 4kW Rh lamp

Influence of gun turning on shooting accuracy

W artykule przedstawiono rozważania dotyczące wpływu skręcenia broni strzeleckiej podczas celowania na, celność strzelania. Z zasad balistyki zewnętrznej wprowadzono zależności pozwalające obliczyć zboczenie pocisku i obniżenie punktu trafienia oraz zaprezentowano wyniki obliczeń dla określonych nastaw celownika przy różnych położeniach celu, wykonane dla różnych kątów skręcenia broni.Turning the gun is the aiming error of frequent occurrence among novice shooters. This error arises when the sighting blade of the rear sight is not horizontal at the moment of a bullet exit. Turning the gun has the great influence on the point of bullet impact. The longer is a distance between the barrel axis and the top of a front sight, the bigger influence for a given gun model, the influence depends on the sight setting and on the shooting range. The Siacci method for flat-fire trajectories calculation was used in the paper. It was assumed that the line of sight. It causes diminishing the elevation angle and moving the muzzle up. The formulas are derived to obtain the bullet lowering ∆γ and the bullet deflection z as a function of the gun turning angle α. It is necessary to know the ballistic coefficient c, the distance m between the barrel axis and the top of front sight, the distance a between the top of the sight plane and the muzzle plane, the distance χtar on which the gun is zeroed, the range χ (may be shorter or longer than the distance) and the turning angle α. Practical computation example for the AKM (Kalashnikov) rifle was presented to illustrate application of the method described. The paper will be of interest for military and sporting shooters which tends to improve their skills

GTAW surface treatment of 7075 aluminum alloy

Microscopic examinations were performed by means of an Olympus GX41 light microscope and a JEOL JSM-6610LV scanning microscope. EDS examinations were carried out using an X-ray microanalyzer by Oxford Instruments

Characterization of Cu/SiC surface composite produced by friction stir processing

The main aim of this work was to obtain a copper matrix surface composite using friction stir processing (FSP). The reinforced phase was SiC particles with an average size of 5 mm. The effect of the reinforcement on the microstructure, hardness and wear behaviour were analysed. The friction treatment was carried out using a truncated cone-shaped tool with a threaded side surface. Multi-chamber technology was used to produce the composite microstructure in the copper surface layer. Changes in the material microstructure were assessed by light microscopy and scanning electron microscopy. Comparative measurement of the hardness of the initial and treated material as well as wear resistance tests were also carried out. A favourable effect of the surface treatment on the microstructure and properties of the copper was found. As a result of the friction treatment there was strong grain refinement in the copper surface layer. The average grain size in the stirring zone was about 3 mm and was over 21 times smaller than the average grain size in the initial material. Intensive dispersion of the SiC particles in the modified layer was also found, leading to the formation of a copper matrix composite. The effect of microstructural changes in the surface layer of the material and formation of the surface composite was an over two-fold increase in the hardness of the material and an increase in wear resistance

Pulse electric generator with a permanent magnet core

Opisano konstrukcję i metodykę badań impulsowego generatora indukcyjnego, który ma być źródłem energii elektrycznej w artyleryjskim zapalniku programowalnym. Rdzeń generatora rozpoczyna ruch po ścięciu przepony, co odpowiada przekroczeniu granicznej wartości przyspieszenia postępowego pocisku poruszającego się w lufie. Zaproponowana metodyka badań generatora polega na wystrzeliwaniu rdzenia za pomocą sprężonego powietrza. Ruch rdzenia rozpoczyna się po zerwaniu przepony, gdy ciśnienie powietrza przekroczy wartość graniczną, która odpowiada obciążeniu rdzenia siłą bezwładności podczas strzału. Podczas eksperymentu rejestrowano w funkcji czasu ciśnienie działające na rdzeń oraz napięcia na cewce generatora i na ładowanym przez generator kondensatorze. Układ był analizowany jako obwód RLC w stanie nieustalonym. Przeprowadzono dynamiczną identyfikacje parametrów obwodu i symulacyjne badania wpływu wartości parametrów na napięcie na kondensatorze.The generator to initiate the prime in fuze for cartridges and it’s methods of study has been described. It consists of a stator with coil of wire and permanent magnet 6 mm diameter core. The core begins its movement as a diaphragm is ruptured, during cartridge acceleration in a gun barrel. Thus generator acts reverse to a coil-gun set. The generator was investigated on a special test stand, with compressed air as a driving medium. The pressure, voltage drop across the coil and the voltage on a condenser was measured as a function of the time. Results of numerical investigations of the RLC circuit, as a simplified model of the generator, are also presented