The presented work discusses the influence of material of foundry mould on the effect of modification of AlSi11 alloy. For this purpose castings were produced in moulds made of four various materials. Castings of the first type were cast in a metal die, the second ones in the conventional mould of bentonite-bound sand, those of the third type in the sand mould with oil binder, the last ones in a shell mould where phenol-formaldehyde resin was applied as a binder. All the castings were made of AlSi11 alloy modified with strontium. For a purpose of comparison also castings made of the non-modified alloy were produced. The castings were examined with regard to their microstructures. The performed investigations point out that the addition of strontium master alloy results in refining of the alloy structure, particularly of the α-phase, causes some morphological changes in the alloy and the refinement of eutectics. The advantageous influence of modifier on the structure of the examined silumin was observed particularly in the case of alloy cast either in the conventional oil-bound sand mould or in the shell mould. The non-modified alloy cast into a metal die exhibits a structure similar to those of modified alloy solidifying in the other moulds. The improvement in both tensile strength and unit elongation suggests that the modification was carried out correctly. The best mechanical properties were found for the alloy cast in a metal die, both with and without modification treatment.
The paper analyses the as-cast state structure of chromium cast iron designed for operation under harsh impact-abrasive conditions. In the process of chromium iron castings manufacture, very strong influence on the structure of this material have the parameters of the technological process. Among others, adding to the Fe-Cr-C alloy the alloying elements like tungsten and titanium leads to the formation of additional carbides in the structure of this cast iron, which may favourably affect the casting properties, including the resistance to abrasive wear.
The article is focused on thermomechanical and plastic properties of two high-manganese TRIPLEX type steels with an internal marking 1043 and 1045. Tensile tests at ambient temperature and at a temperature interval 600°C to 1100°C were performed for these heats with a different chemical composition. After the samples having been ruptured, ductility was observed which was expressed by reduction of material after the tensile test. Then the stacking fault energy was calculated and dilatation of both high-manganese steels was measured. At ambient temperature (20°C), 1043 heat featured higher tensile strength by 66MPa than 1045 heat. Microhardness was higher by 8HV0,2 for 1045 steel than for 1043 steel (203HV0,2). At 20°C, ductility only differed by 3% for the both heats. Decrease of tensile properties occurred at higher temperatures of 600 up to 1100°C. This tensile properties decrease at high temperatures is evident for most of metals. The strength level difference of the both heats in the temperature range 20°C up to 1100°C corresponded to 83 MPa, while between 600°C and 1100°C the difference was only 18 MPa. In the temperature range 600°C to 800°C, a decrease in ductility values down to 14 % (1045 heat), or 22 % (1043 heat), was noticed. This decrease was accompanied with occurrence of complex Aluminium oxides in a superposition with detected AlN particles. Further ductility decrease was only noted for 1043 heat where higher occurrence of shrinkag porosity was observed which might have contributed to a slight decrease in reduction of area values in the temperature range 900°C to 1100°C, in contrast to 1045 heat matrix.
Porosity is one of the major defects in aluminum castings and results in a decrease of the mechanical properties of Al-Si alloys. It is induced by two mechanisms: solidification shrinkage and gas segregation. One of the methods for complex evaluation of macro and micro porosity in Al-Si alloys is using the Tatur test technique. This article deals with the evaluation of porosity with the help of Tatur tests for selected Al-Si alloys. These results will be compared with results obtained from the ProCAST simulation software.
As part of the studies conducted in the field of broadly understood casting of non-ferrous metals, selected results on the impact of variable additions of copper and silicon in aluminium were presented. A series of melts was carried out with copper content kept constant at a level of 2% (1st stage) and 4% (2nd stage) and variable contents of silicon introduced into aluminium. The crystallization characteristics of the examined alloys and the percentage of structural constituents at ambient temperature were obtained by modelling the thermodynamic parameters of individual phases with the CALPHAD method. The microstructure of the obtained alloys was examined and microhardness was measured by the Vickers-Hanemann method. The alloy properties were assessed based on the results of mechanical tests, including ultimate tensile strength (UTS), hardness (BHN) and elongation (E). The machinability of the tested alloys was analyzed in a machinability test carried out by the Keep-Bauer method, which consisted in drilling with a constant feed force.
The obtained results clearly indicate changes in the images of microstructure, such as the reduction in grain size, solution hardening and precipitation hardening. The changes in the microstructure are also reflected in the results of mechanical properties testing, causing an increase in strength and hardness, and plasticity variations in the range of 4 ÷ 16%, mainly due to the introduced additions of copper and silicon. The process of alloy strengthening is also visible in the results of machinability tests. The plotted curves showing the depth of the hole as a function of time and the images of chips produced during the test indicate an improvement in the wear resistance obtained for the tested group of aluminium alloys with the additions of copper and silicon.
Fabrication and microstructure of the AlSi11 matrix composite containing 10 % volume fraction of CrFe30C8 particles were presented in this paper. Composite suspension was manufactured by using mechanical stirring. During stirring process the temperature of liquid metal, time of mixing and rotational speed of mixer were fixed. After stirring process composite suspension was gravity cast into shell mould. The composites were cast, applying simultaneously an electromagnetic field. The aim of the present study was to determine the effect of changes in the frequency of the current power inductor on the morphology of the reinforcing phase in the aluminum matrix. The concept is based on the assumption that a chromium-iron matrix of CrFe30C8 particles dissolves and residual carbide phases will substantially strengthen the composite. The microstructure and interface structure of the AlSi11/CrFe30C8 composite has been studied by optical microscopy, scanning microscopy and X-ray diffraction.
The dimensional accuracy of a final casting of Inconel 738 LC alloy is affected by many aspects. One of them is the choice of method and time of cooling the wax model for precision investment casting. The main objective of this work was to study the initial deformation of the complex shape of a rotor blades casting. Various approaches have been tested for cooling a wax pattern. When wax models are air cooled and without clamping in the jig for cooling, deviations from the ideal shape of the casting are very noticeable (up to 8 mm) and most are in extreme positions of the model. When the blade is cooled in the fixing jig in a water environment, the resulting deviations compared to those of air cooling are significantly larger, sometimes up to 10 mm. This itself does not mean that the final shape of the casting is dimensionally more accurate with the usage of wax models, which have smaller deviations from the ideal position. Another deformation occurs when the shell mould is produced around the wax pattern and further deformations emerge while cooling the blade casting. This paper demonstrates the first steps in describing the complex process of deformations occurring in Inconel alloy blades produced with investment casting technology by comparing results of thermal imagery, simulations in foundry simulation software ProCAST 2010, and measurements from a CNC scanning system using a Carl Zeiss MC 850. Conclusions are so far not groundbreaking, but it seems that deformations of the wax pattern and deformations of the castings do in some cases cancel each other by having opposite directions. Describing the whole process of deformations will help increase the precision of blade castings so that the models at the beginning and the blades in the end are the same.
The results of studies on the use of magnesium alloy in modern Tundish + Cored Wire injection method for production of vermicular graphite cast irons were described. The injection of Mg Cored Wire length is a treatment method which can be used to process iron melted in an electric induction furnace. This paper describes the results of using a high-magnesium ferrosilicon alloy in cored wire for the production of vermicular graphite cast irons at the; Tundish + Cored Wire to be injected methods (PE) for pearlitic-ferritic matrix GJV with about 25 %ferrite content. The results of calculations and experiments have indicated the length of the Cored Wire to be injected basing on the initial sulfur content and weight of the treated melt. The paper presents a microstructure matrix and vermicular graphite in standard sample and different walled castings. The results of numerous trials have shown that the magnesium Tundish + PE Method process can produce high quality vermicular graphite irons under the specific industrial conditions of the above mentioned foundries.
Changes of gas pressure in the moulding sand in the zone adjacent to mould cavity were analysed during pouring of cast iron. No significant effect of pressure on the surface quality of castings was observed. In the second series of tests, the concentration of hydrogen in the gas atmosphere was measured. It has been found that the value of this concentration depends on metal composition and is particularly high in cast iron containing magnesium. This is due to the reduction of water vapour with the element that has high affinity to oxygen. The presence of hydrogen causes the formation of gas-induced defects on the casting surface.