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Aluminium alloys with higher content of alloying elements are very susceptible to the emergence of crystal segregation that significantly affects the mechanical, physical and chemical properties of these alloys. Crystal segregation is called chemical heterogeneity in microscale and is formed during crystallization. Crystallization of alloys does not occur at a particular temperature, as is the case of pure metals, but in a certain temperature interval. During cooling of the melt occurs to formation of different regions within the dendritic cell that differs in chemical composition. Generally is crystal segregation defined as chemical heterogeneity formed during alloy crystallization that is enriched or deprived of alloying elements and impurities that segregate unevenly across the surface of the dendrites. In the central area of the dendritic cells is alloy deprived of alloying elements, while the outer parts of dendritic cells and in space between dendrites is the concentration of alloying elements richer. This concentration has a hyperbolic course, when the central region of dendritic cells has the lowest concentration of the alloying elements and the outer part of dendrite boughs and interdendritic space have the maximum. Distribution of individual elements has a recurring character and can be described by sine function. The distance between two main axes of dendritic cells is affected by the temperature interval between the liquidus and solidus for the given alloy, the cooling rate of the melt and temperature gradient during solidification. Formation of the crystal segregation in aluminium alloys rich in alloying element and additives cannot be prevented, it is possible only influence its scope and with the right choice of heat treatment parameters can be suppressed. To suppress the crystal segregation the castings are subjected to heat treatment which is called homogenization annealing. It is the diffusion process in which there occurs to a balancing of chemical composition of alloy and the uniformity of its structure.

The microstructure and mechanical properties of castings made of alloy Al+3%Mg were studied along with a tire mold made by low-pressure casting. The microstructure of the alloy was analyzed by optical microscopy, and scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to perform a detailed analysis of its structural components. Static tests of tensile strength were conducted and Brinell hardness was measured to evaluate its mechanical properties. The tensile tests were carried out at normal and elevated temperatures in order to simulate the service conditions of the mold.

Crystal segregation is taken as chemical heterogeneity under the micro-scale and it develops during the crystalli-zation process. Alloy crystallization does not take place under a particular temperature, as it happens in the case of pure metals, but it runs under a certain temperature interval. When cooling the melt, various places start devel-opment among dendritic cells which differ in their chemical composition. Crystal segregation can be generally defined as chemical heterogeneity developing during the alloy crystallization process, and it can be either en-riched or in contrast depleted with alloying elements and impurities, which are unevenly segregating over the en-tire dendritic surface. In the central part of the dendritic cells there is an alloy, which is depleted with alloying elements, while the edge areas of dendritic cells and interdendrite space present higher concentration of alloying elements. This concentration shows a hyperbolic development; when the central part of dendritic cells area has the lowest alloying elements concentration, while the edge part of a dendritic tree and the interdendrite space show the maximum concentration. The distance between two main axes of dendritic cells is affected by the temperature interval running between the liquid and solid phase of the chosen alloy, as well as by melt cooling rate and temper-ature gradient during the solidification phase. The shorter distance between the axes of dendritic cells appears under faster cooling, which allows very fast heat dissipation and creates very fine structure of the resulting alloy. The longer distance between the main axes of dendritic cells stimulates greater segregation appearing under slow melt cooling. Crystal segregation formation of aluminum alloys enriched with alloying elements and impurities cannot be pre-vented, only its extension can be regulated and it can be suppressed with the correct choice of heat treatment pa-rameters. To suppress the crystal segregation the casts should undergo heat treatment which is called homogenization annealing.

Classification of the mineability of rocks is an integral part of the earthworks occurring in the implementation of engineering works. The existence of degrees of excavation difficulty allows us to specify the needs of mechanisms for earthworks. It is determined according to the old standard CSN 73 3050, and new standard CSN 73 6133. Both standards define the mechanical mechanisms that should be used for each degrees of excavation difficulty. Based on this rock may be the most optimal breakage and extracted without machine selection would have been undersized. That would mean its destruction and inefficient extraction of rocks, or contrary oversizing. On that basis, there would be an unreasonable overpricing earthworks. Into force has already entered a new standard but there are a number of differences in their classification. The publication deals with the evaluation degrees of excavation difficulty, and mechanical mechanisms for earthwork and differences between the two standards, respectively their similarities. It is evident that the old standard represents a very detailed division of soil and rock into seven degrees of excavation difficulty and thus represents a substantially transparent calculation of the total price of earthworks. In contrast, the new standard gives only three degrees of excavation difficulty. This represents a major simplification of the process of classification and subsequent utilization of engineering mechanisms.

In the course of homogenizing annealing of aluminium alloys being cast continually or semi-continually it appears that chemical inhomogenity takes off within separate dendritic cells (crystal segregation). It is about a diffusion process that takes place at the temperature which approaches the liquid temperature of the material. In that process the transition of soluble intermetallic compounds and eutectic to solid solution occurs and it suppresses crystal segregation significantly [1]. The temperature, homogenization time, the size of dendritic cells and diffusion length influences homogenizing process. The article explores the optimization of homogenizing process in terms of its time and homogenizing annealing temperature which influence mechanical properties of AlZn5,5Mg2,5Cu1,5 alloy.

This paper deals with the evaluation of the corrosion resistance of the Al-Si alloys alloyed with the different amount of antimony. Specifically it goes about the alloy AlSi7Mg0,3 which is antimony alloyed in the concentrations 0; 0,001; 0,005; 0,01 a 0,05 wt. % of antimony. The introduction of the paper is dedicated to the theory of the aluminium alloys corrosion resistance, testing and evaluation of the corrosion resistance. The influence of the antimony to the Al-Si alloys properties is described further in the introduction. The experimental part describes the experimental samples which were prepared for the experiment and further they were exposed to the loading in the atmospheric conditions for a period of the 3 months. The experimental samples were evaluated macroscopically and microscopically. The results of the experiment were documented and the conclusions in terms of the antimony impact to the corrosion resistance of the Al-Si alloy were concluded. There was compared the corrosion resistance of the Al-Si alloy antimony alloyed (with the different antimony content) with the results of the Al-Si alloy without the alloying after the corrosion load in the atmospheric conditions in the experiment.

Гомогенізація визначається як метод термічної обробки, який складається з тимчасової витримки при високій температурі поблизу ліквідуса (приблизно від 0,7 до 0,8 температури плавлення), щоб усунути хімічну неоднорідність дифузії. Температура та тривалість процесу гомогенізації обрана так, щоб вийшло розчинення рівноваги інтерметалевих фаз, що утворюються в процесі кристалізації і подальшого розповсюдження елементів у твердих α рішеннях. Homogenization is defined as a method of heat treatment, which consists of holding time at high temperature near the liquidus (approx. 0.7 to 0.8 the melting temperature) to eliminate chemical inhomogeneity diffusion processes. Cause of segregation is selective crystal solidification in the gradual change in composition of the solid phase. Melt began to appear after certain of the hypothermia during cooling, and the growth of germs in accordance with the general laws of crystallization. Each rigid layer has a different chemical composition. The first part of the solid phase ingredient low concentration of the element last, on the contrary, very high. Susceptibility to crystal alloy segregation is greater, the greater the temperature interval solidification of alloys and the horizontal distance between the liquidus and solidus lines. Crystal segregation will also increase with increasing content of alloying elements, which in these experimental alloys occurs as containing 6-9% alloying elements. Crystal segregation can be removed by diffusion, for which it is necessary to create conditions by homogenization annealing. Гомогенизация определяется как метод термической обработки, который состоит из временной выдержки при высокой температуре вблизи ликвидуса (примерно от 0,7 до 0,8 температуры плавления), чтобы устранить химическую неоднородность диффузии. Температура и длительности процесса гомогенизации выбрана так, чтобы получилось растворение равновесия интерметаллических фаз, образующихся в процессе кристаллизации и последующего распространения элементов в твердых α решениях.

The publication aims to bring undoubted importance approximate table bearing capacity of gravel soils, which are used in the new constructions. Tabulated values enable to determine the estimated bearing capacity of foundation soil for a simple and inexpensive construction to a depth of 1 meter. In the publication there are compares particular class of gravel soils in depending on the width of the base and ingredients of fine-grained soil. Gravelly soils are the best foundation soil in terms of bearing capacity, but the amount of fine-grained soils or poorly grained gravel, or gravel with a low value of compactness can greatly reduce this value. © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of organizing committee of the World Multidisciplinary Earth Sciences Symposium (WMESS2016)

The application of geosynthetic materials has become an ordinary part of not only transport constructions. Such materials are very versatile depending on the earth construction requirements and soil character. With regard to their popularity in use, research and development of new material and innovations of the existing ones are under way, so that the demands on their usability were met and their long life was ensured. According to their production methods, geosynthetics may be classified into basic groups of woven, non-woven and knitted materials. According to their function, which is expected from the different types of geosynthetics, we distinguish geosynthetics with a filtration, separation, protection barrier, erosion control, drainage and reinforcement functions. However, the application of the geosynthetic materials is not possible without a conveniently prepared subgrade. The use of heavy machinery thus becomes an important step in the implementation of transport constructions. Without quality preparation of the surface and subgrade of the body, the effectiveness of the geosynthetics would be supressed and their life would be much shorter. This could lead to deformations and cause fatal consequences to the overall transport structure. A set of earth works, depending on the type of transport structure, precedes the laying of the geosynthetic material. In general, heavy machinery is used to handle earth in extraction or filling, removal of unsuitable sharp-edged stones and other undesirable objects, to even the surface and to compact it. The article deals with the building machines vital for the preparation of the earth body before the application of geosynthetics. At the same time, it mentions the basic types of geosynthetic materials used in transport constructions.

Proposal soil characteristics represent the most important physical-mechanical parameters for foundation engineering purposes. At present, there are a number of databases produced by the Czech Geological Survey, which building companies use free of charge. Further to the existing data, the databases could be completed with the proposal soil characteristics that would provide free information on the benchmark characteristics of different foundation soils in a modern, fast and easy manner, and thus facilitated its preliminary assessment. In the future, such data could be interconnected with the database information on borehole exploration, slope instabilities, information on the area geology, etc., on the basis of which could be generated a complex preliminary assessment report whether a locality is suitable for foundation engineering purposes. This would render a fast and easy orientation in the given locality even before the survey itself and would be completely free of charge.

Aluminium alloys with higher content of alloying elements are very susceptible to the emergence of crystal segregation that significantly affects the mechanical, physical and chemical properties of these alloys. Crystal segregation is called chemical heterogeneity in microscale and is formed during crystallization. Crystallization of alloys does not occur at a particular temperature, as is the case of pure metals, but in a certain temperature interval. During cooling of the melt occurs to formation of different regions within the dendritic cell that differs in chemical composition. Generally is crystal segregation defined as chemical heterogeneity formed during alloy crystallization that is enriched or deprived of alloying elements and impurities that segregate unevenly across the surface of the dendrites. In the central area of the dendritic cells is alloy deprived of alloying elements, while the outer parts of dendritic cells and in space between dendrites is the concentration of alloying elements richer. This concentration has a hyperbolic course, when the central region of dendritic cells has the lowest concentration of the alloying elements and the outer part of dendrite boughs and interdendritic space have the maximum. Distribution of individual elements has a recurring character and can be described by sine function. The distance between two main axes of dendritic cells is affected by the temperature interval between the liquidus and solidus for the given alloy, the cooling rate of the melt and temperature gradient during solidification. Formation of the crystal segregation in aluminium alloys rich in alloying element and additives cannot be prevented, it is possible only influence its scope and with the right choice of heat treatment parameters can be suppressed. To suppress the crystal segregation the castings are subjected to heat treatment which is called homogenization annealing. It is the diffusion process in which there occurs to a balancing of chemical composition of alloy and the uniformity of its structure.