Geopolymers compete with a number of conventional coatings and a few of them have already been replaced. The aim of this work was the analysis of alkali-activated metakaolin-based geopolymers and their use as brush-applied coatings, which were chosen due to their simplicity and cost-effectiveness. Eight coatings were prepared and the AlMgSi aluminum alloy underlying the substrate was also studied. The main characterizations of the prepared coatings were the microscopy analysis, which showed that manual painting with a brush on the coatings we prepared could achieve a high-quality geopolymer layer, and that if microscopic cracks are visible on the surface, they are uniform and do not affect the resulting cohesiveness of the coating. The thicknesses of these coatings are different, ranging from 1.5 to 11 μm, with no visible anomalies. For the evaluation of the properties of the coatings, we determined the analysis of adhesion to the adjacent substrate, microhardness and thermal expansion determined using the so-called dilatometric analysis as important criteria. For these analyses, the results vary by geopolymer type and are discussed in the following chapters.
In terms of physical and chemical properties, titanium and its alloys are among the most important construction materials today. The Ti6Al4V alloy can be classified among high-strength materials with good plasticity, corrosion resistance and other valuable properties. When performing operations associated with long-term heating of workpieces and parts made of titanium alloys in an air atmosphere, a TiO2 layer is formed on the surface of the product. Ti6Al4V alloy, also known as Ti64, in terms of microstructure is a two-phase alloy formed by α+β solid solutions, which has excellent corrosion resistance and biocompatibility. This alloy is also suitable for jet engines, gas turbines and many aircraft components, as well as in biomedicine. Heat treatment can further improve its technical properties, reduces stress, improves machinability, fracture toughness. The surface of alloys can also be thermally stressed when micro and nano layers of material are applied, which serve to extend the life of products made of this alloy. The presented article analyzes the effect of heat treatment at temperatures of 550 °C and 600 °C and corrosion load with salt fog in the range of 168 to 720 hours on the microstructure and microhardness of the Ti6Al4V alloy.
Titanium alloys are among the biocompatible materials that are used for biomedical implants. From the point of view of the reactivity of the human body, it is important to know the state of the surface of these materials, which in technical practice is represented by the term surface integrity, which includes a complex of evaluated properties. One of the classic approaches is the evaluation of the surface roughness and the properties of the stable oxide layer, which influence the formation of the connection of the implant with human tissues and influence its acceptance. Another frequent approach is the use of optical metallography, especially for the assessment of material thickness, distribution and character of corrosion attack. Less common is the use of electron microscopy in the evaluation of the surface, which in this case is affected by the action of corrosion. Samples of both pure titanium and Ti6Al4V alloy were divided into sets according to surface roughness and subsequently exposed to corrosion for different periods of time. The presented article is devoted to basic analyzes of the effect of roughness on corrosion behavior using not only classical optical but also electron microscopy.
This article deals with the issue of silumin inoculation. Two alloys, AlSi7Mg0.3 and AlSi10.5Cu1.2Mn0.8Ni1.2, were selected. 4 pieces of castings were cast from each alloy. One casting was not inoculated and 3 castings were inoculated using AlTi5B1 prealloy in concentrations of 0.05 wt. %, 0.1 wt % and 0.2 wt. % Ti. The castings were cast into metal molds preheated to a temperature of 200°C ± 5°C. In total, 8 pieces of metallographic cuttings were prepared for each alloy. Four samples were taken from the bottom part of the casting and four samples from the middle part of the casting. Secondary axes of DAS dendrites were measured using a microscope. Subsequently, the microhardness of the solid solution α was measured according to Vickers.
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