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Search Results: 1 - 10 of 461888 matches for " A. Zyska "
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The influence of graphite particles on supercooling of composite suspension
M. ??giewka,Z. Konopka,A. Zyska
Archives of Foundry Engineering , 2007,
Abstract: The work presents the solidification kinetics of a composite suspension with graphite particles dispersed in AlMg10 alloy matrix during its flow along a runner. The temperature field for investigated materials has been determined by measuring the suspension temperature values during flow and solidification in the elongated runner-like mould cavity. The influence of the quantity of ceramic particles on the temperature of the solidification beginning has been shown, and by the same its influence on the supercooling of the flowing composite suspension. Differences between the supercooling values for matrix alloy and for composites have been revealed. The obtained results have been interpreted pointing to the influence of graphite particles on activating the nucleation and change of the heat exchange conditions between the flowing suspension and the mould wall.
The influence of the Ni layer covering carbon fibre on the AK132 matrix structure
A. Zyska,Z. Konopka,M. ??giewka
Archives of Foundry Engineering , 2007,
Abstract: The quality and the quantity assessment of the structure of the AlSi13Cu2 alloy matrix composites reinforced with carbon fibre in the amount of 5, 10, or 15 vol. percent has been presented. Due to the poor wettability of carbon fibre by molten AlSi alloy and the low castability of the examined composites, the Ni-covered fibre with 0.25 μm thick Ni layer has been used and the pressure casting technology has been employed. The chemical interaction between Ni layer and the molten AlSi alloy has been estimated in the thermodynamic aspect using the Thermo-Calc calculation packet as well as performing the microstructural investigations by means of transmission electron microscope. Simulations of solidifying have been carried out and the phase composition of the metal matrix has been determined. Microstructural examinations have proved that the total dissolving of the Ni layer occurs under the conditions of composite production and the phases of the Al3Ni type (Fe and Cu dopped) arise. These phases occur in the form of independent precipitates in the whole volume of matrix as well as the ones locally grouped around the carbon fibres.
Evaluation of the heat transfer coefficient at the metal-mould interface during flow
Z. Konopka,M. ??giewka,A. Zyska
Archives of Foundry Engineering , 2007,
Abstract: Calculation results concerning the heat transfer coefficient at the metal-mould interface during flow of the AlMg10 alloy in the channel-like cavity of the spiral castability test mould. The experimental cooling curve as well as changes of metal flow velocity have been determined on the basis of the measured metal temperature during flow. The cooling curve equation for the examined alloy, derived from the heat balance condition in a casting-mould system and taking into account experimental data concerning changes in metal temperature and its flow velocity, has enabled evaluation of the heat transfer coefficient at a chosen point of a metal stream along the mould channel. Graphic representations of changes of this coefficient against time and the channel length have been shown.
The solidification of squeeze cast AlCu4Ti alloy
A. Zyska,Z. Konopka,M. ??giewka
Archives of Foundry Engineering , 2007,
Abstract: The results of examining the solidification process of the squeeze cast AlCu4Ti alloy have been presented. A simulation of the alloysolidification has been described for both the equilibrium conditions taking into account squeeze pressure and the non-equilibrium conditions under the assumption of the lack of diffusion in the solid state (Scheil model). Experiments have been held for plate castings squeezed under the pressure ranging from the atmospheric one to the value of 90 MPa. The derivative differential thermal analysis (DDTA) method has been used for determining the phase transition point, solidification rate and the degree of alloy supercooling dependent on the squeeze pressure. It has been found that the solidification rate is increased by almost seven times for squeeze castings as compared with the gravity castings. Squeezing causes also a significant refinement of the alloy dendritic structure and removes gas and shrinkage porosity, characteristic for die castings. The high quality AlCu4Ti-alloy castings can be obtained already at the 30 MPa pressure.
The influence of graphite particles on solidification of composite suspension during flow
Z. Konopka,M. ??giewka,A. Zyska
Archives of Foundry Engineering , 2007,
Abstract: The measurements concerning the temperature field of the composite suspension with AlMg10 alloy matrix reinforced with graphite particles during its flow in a runner-like mould cavity have been performed for the purpose of investigating the influence of the graphite particles on the solidification kinetics. Applying the derivative differential thermal analysis method, the kinetics of solidification heat release has been calculated for examined composites. The time-dependent quantity of solid phase crystallized over the period of flow has been determined on this basis. The dependence of the solid phase quantity upon the momentary length of the experimental casting has apportioned the length of the solidification zone in the casting and the critical fraction of solid phase at which the flow stops. The solidification zone is longer and the critical fraction of solid phase at the stream front is lower for composite containing 10% of graphite particles than for the one with 20% of graphite. The composite reinforced with 20% of graphite particles flows at a significantly lower rate and exhibits reduced castability as compared with the composite with 10% of graphite. It is caused by the higher solidification rate in the initial stage of the process. The obtained results allow for supposing that graphite particles intensify composite solidification by changing the kinetics of the process.
The ‘full sleeve’ application in the horizontal cold-chamber machine for pressure die casting of aluminium alloys
Z. Konopka,A. Zyska,M. ??giewka,A. Bielecka
Archives of Foundry Engineering , 2008,
Abstract: The ‘full sleeve’ construction has been designed and accomplished in the horizontal cold-chamber pressure die casting machine. Main part of this solution is a counter plunger placed in a movable die half which allows for full filling of the shot sleeve and precisely fixes the metal quantity needed for casting. The purpose of this new construction solution is mainly the reduction of the casting porosity caused by air entrapment and the improvement of both castability and accuracy of the die cavity reproduction. For such a redesigned machine there have been performed examinations consisting in pressure casting of AlSi9Cu alloy (EN AC-46000) at varying plunger velocity in the second stage of injection and varying intensification pressure. The alloy castability (the die filling ability) has been measured for each parameter setting. For the purpose of comparison, similar measurements have been performed also for the conventional system without a counter plunger. The castability examination has been done by means of a specially designed die with an impression of a trial casting of variable wall thickness. The experiments have been held according to the assumed factor design 22, what allowed for determining the mathematical models describing the influence of die filling parameters on the castability and the die cavity reproduction level. Both alternatives of the experiment confirmed the positive influence of plunger velocity and intensification pressure increase on the improvement of castability, the measure of the latter being the filled length of the impression. Applying of the new ‘full sleeve’ solution has improved castability for each experiment by about 20% as compared with conventional alternative. Castability in the ‘full sleeve’ system has been increased even for low values of plunger velocity and intensification pressure. For both alternative systems the influence of plunger velocity has been found, as an average, by four times greater than the influence of intensification pressure. The possibility of applying lower pressure values has been noticed for the shot sleeve construction with the counter plunger. This can influence favourably both the die and the machine durability. The obtained results have been explained and it has been pointed out that the ‘full sleeve’ construction can be widely adopted in pressure die casting of metal alloys.
The solidification during flow of composite suspension in the permanent mould
M. ??giewka,Z. Konopka,A. Zyska,M. Nadolski
Archives of Foundry Engineering , 2011,
Abstract: The presented work presents the influence of graphite particles on the solidification kinetics of metal suspension based on AlSi10Mgalloy during the die cavity filling. In order to examine this problem, the measurements concerning temperature changes in the selected points of the metal mould have been taken for two materials poured into the die: the pure AlSi10Mg alloy and the alloy reinforced with graphite particles. Thus the solidification and cooling curves of the examined material have been achieved. The recorded temperaturechanges have served as a basis for preparing graphs representing the velocity of the metal stream and the distance travelled by the front of the stream against the time. The introduction of graphite particles into the matrix alloy has caused the shortening of the distance flown by the material by 50% as compared with the non-reinforced alloy. The recorded temperature changes have allowed also for determining the temperature changes for the front of the metal stream during the die filling. Taking into account these results it has been found that the AlSi10Mg+10%Cgr composite begins its solidification after having covered the distance seven times shorter than the corresponding distance measured for the non-reinforced AlSi10Mg alloy.
Influence of solidification rate on microstructure of gravity cast AZ91 magnesium alloy
K.N. Braszczyńska-Malik,A. Zyska
Archives of Foundry Engineering , 2010,
Abstract: Derivative thermal (ATD) and microstructure analyses of gravity cast AZ91 magnesium alloy are presented. The alloy was cast into cold steel and sand moulds with the same dimensions. ATD curves – solidification curves and their first derivative – are presented. The investigated alloy exhibited a strong alloying elements segregation and the presence of solid solution and (Mg17Al12) eutectic mixture. Discontinuous precipitates of phase were also observed in the microstructure of AZ91 cast into sand mould.
The assessment of bell casting producibility based on computer simulation of pouring and solidification
M. Nadolski,A. Zyska,Z. Konopka,M. ??giewka
Archives of Foundry Engineering , 2011,
Abstract: The work estimates the possibility of modification of the traditional production method of bell castings taking into account calculations performed by NovaFlow&Solid simulation program. Changes are evaluated with regard to the arrangement of the shrinkage defects in castings, which are of influence on the acoustic and mechanical properties of castings.
Analysis of the failure causes in an element made of AlSi11Cu2(Fe) alloy
G. Golański,A. Zyska,K. Werner,H. Stok?osa
Archives of Foundry Engineering , 2011,
Abstract: The paper presents results of research on a cross element damaged during the service, made of the casting alloy of aluminum -AlSi11Cu2(Fe) (AK132). Performed research was to explain the reasons for this damage and included microstructural observation as wellas the investigation on mechanical properties. On the basis of the tests carried out it has been noticed that there is significantinhomogeneity of the structure characterized by the presence of both: normally modified eutectic areas (α + Si) and needle-shaped primarysilicon crystals. On the cross-section of the cast wall there were numerous casting defects of diverse size observed – shrinkage porosity.On the basis of the research it has been concluded that the damage of the examined element occurred as a result of fatigue crackinginitiated from the surface near the marks left by the knock-outs, while the subsequent propagation of the crack ran along the primaryprecipitates of silicon crystals as well as through the crystals.
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