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1
Content available Review on Oxide Formation and Aluminum Recovery Mechanism during Secondary Smelting
Osoba L.O., Owolabi O.B., Talabi S.I., Adeosun S.O.
Journal of Casting & Materials Engineering
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2018
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Vol. 2, no. 2
45-51
EN
The remelting, refining, and casting process of aluminum alloys often generate aluminum dross containing primarily oxides and nitrides of aluminum and entrapped metallic aluminum at the surface of the molten metal as a result of reactions within the furnace atmosphere at elevated temperatures. The handling of dross is an expensive but necessary activity during aluminum smelting. Furthermore, the amorphous Al2O3 oxide film formed on the pure molten aluminum surface due to the liquid metal randomly distributed atoms is impermeable to the diffusion of aluminum metal and oxygen. In amorphous materials, there is a low mobility of the charge carriers and an absence of preferred diffusion paths. This film can transform to crystalline Al2O3 by nucleation and grows with time and opportunity. This review discusses the mechanism of oxide formation and the aluminum metal recovery processes.
2
Content available Dependence of Reoxidation Effect on a Type of Gating System in Investment Casting Technology
Herman A., Vratny O.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 3
107--112
EN
Nowadays, there are growing demands on the accuracy of production. Most of this is reflected in precise manufacturing, such as the investment casting process. Foundries are looking for causes of defects in some cases for a very long time, and it may happen that the source of defects is completely different from what was originally assumed. During the casting process there exist potential causes of defects as oxygen inclusions. This paper represents a summary of the beginnings of a wider research that will address the problems of gating systems in investment casting technology. In general, the influence of the melt flow is underestimated and the aim of the whole scientific research is to demonstrate the significant influence of laminar or turbulent flow on the resulting casting quality. Specifically, the paper deals with the analysis of the most frequent types of defects found in castings made of expensive types of materials casted in an open atmosphere and demonstration of connection with the design of gating systems in the future.
3
Content available Reoxidation Processes Prediction in Gating System by Numerical Simulation for Aluminium Alloys
Bruna M., Bolibruchova D., Pastričák R.
Archives of Foundry Engineering
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2017
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Vol. 17, iss. 3
23--26
EN
Pouring of liquid aluminium is typically accompanied by disturbance of the free surface. During these disturbances, the free surface oxide films can be entrained in the bulk of liquid, also pockets of air can be accidentally trapped in this oxide films. The resultant scattering of porosity in castings seems nearly always to originate from the pockets of entrained air in oxide films. Latest version of ProCast software allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up in casts. During a filling calculation, ProCast can calculate different indicators which allow to better quantify the filling pattern. The fluid front tracking indicator “ Free surface time exposure” has the units [cm2s]. At each point of the free surface, the free surface area is multiplied by the time. This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow. Experiments to validate this new functions were executed.
4
Content available Simulation of Casting Technologies for Al-Si-Cu Plate Casting
Cupido L. H., Żak P. L.
Archives of Foundry Engineering
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2013
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Vol. 13, iss. 3 spec.
11--14
EN
During the casting of aluminium alloys, the susceptibility to form oxide films is high, due to the turbulent flow of the melt and constant exposure of new surface area. This have impact on the properties of the material and the service life of the casting components. Also, hydrogen solubility in the solid state are very low, which ends up being rejected and causing porosity. After pouring, when solidification occurs, another phenomenon arise called shrinkage. This require excess molten metal to be fed during this phase change to eliminate or reduce the effect of volumetric changes. Filling and feeding during aluminium casting is therefore of paramount importance, and careful steps needs to be undertaken to reduce possible defects in the castings. The objective is to apply studied literature guides and rules and simulate the casting process of aluminium alloys, and understand the how certain defects are occurring during this process. This is a preliminary study towards the understanding of the “macro evolution” of Al-Si-Cu alloy during solidification, which will be the bases for the study of microsegregation of the specified alloy.
5
Content available remote Properties of oxide films produced on surface of aluminum alloys
Płonka S., Lorek R.
Advances in Manufacturing Science and Technology
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2010
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Vol. 34, nr 3
33-47
EN
The paper presents results of 3D geometric structure of the surface of Al2O3 oxide films generated in the following aluminum alloys: AlCu4Mg1, AlSi1MgMn and AlZn9Si7. There are presented hardness distributions on depth of the oxide film obtained in result of hard electrolytic oxidation, investigation of microstructure of this film with use of the BSE detector, and microanalysis of chemical composition performed with use of the EDS detector. One has undertaken an attempt of selection of aluminum alloy type to production of rotors to open end spinning machines, with respect to selected parameters of surface topography and maximal hardness of the oxide film.
PL
W pracy przedstawiono wyniki badań struktury geometrycznej powierzchni 3D warstw tlenkowych Al2O3 i wytworzonych na stopach aluminium: AICu4Mg1 i AlSi1MgMn oraz AlZn9Si7. Określono rozkład twardości na głębokości warstwy tlenkowej uzyskanej w wyniku utleniania elektrolitycznego twardego. Przedstawiono wyniki badania mikrostruktury warstwy oraz analizę składu chemicznego wykonaną przy użyciu odpowiednio detektorów BSE i EDS. Podjęto próbę doboru stopu aluminium na rotory przędzarek bezwrzecionowych, z uwzględnieniem przyjętych parametrów topografii powierzchni, oraz maksymalne twardości warstwy tlenkowej.
6
Content available remote An establish attempt of reasons of machining splinter formation in AC44200 alloy high pressure die castings
Mutwil J.
Archives of Foundry Engineering
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2008
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Vol. 8, iss. 3
159-166
EN
A problem of splinter formation during machining the AC44200 alloy high pressure die casting has been experimental investigated. In order to establish the reason of this occurrence a set of 200 high pressure die casting of the tensile strength samples have been prepared. The tensile tests were carried out using a Zwick Z050 universal testing machine. JM-SPC program has been used for statistical analysis of test results. A large variability of tensile strength results has been found. In order to find the reason of this variability the fracture surface investigations (macrographs for all of samples and SEM micrographs for chosen samples) have been carried out. It has been establish that in all cases a significant decrease of tensile strength was caused by presence of inclusions or porosity. In lot of cases the inclusions have a form of oxide film.
7
Content available remote Oxide layers on implanted GaAs surfaces: X-ray photoelectron spectroscopy and ellipsometry study
Kulik M., Saied S.O., Liśkiewicz J.
Nukleonika
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1999
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Vol. 44, nr 2
167-174
EN
The chemical composition of an oxide on the GaAs surface implanted with Xe and Ar ions at various doses was studied by x-ray-photoelectron spectroscopy (XPS). It was found that only the dose of the introduced admixtures, and thereby the number of occurring defects can influence the kind of oxide covering surface. From the ellipsometric measurements it was found that the layer thickness of the oxide on the GaAs surface increases monotonically with the increasing dose implanted and reaches a certain saturation level for the samples exposed to ions at an amorphizing dose.
PL
Metodą XPS badano skład chemiczny tlenku na powierzchni GaAs implantowanego różnymi dawkami jonów Ar i Xe. Stwierdzono, że dawka jonów powodująca amorfizację warstwy domieszkowanej ma wpływ na rodzaj tlenku pokrywającego badane powierzchnie. Na podstawie badań elipsometrycznych stwierdzono, że grubość warstwy tlenku na powierzchni GaAs wzrasta wraz ze wzrostem dawki wprowadzonej domieszki i osiąga pewne nasycenie dla próbek naświetlanych dawką amorfizującą.
8
Quantitative characterisation of alumina scales on high temperature alloys by atomic force microscopy.
Czyrska-Filemonowicz A., Szot K., Wasilkowska A., Breuer U., Quadakkers W.J.
Inżynieria Materiałowa
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1998
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R. XIX, nr 4
1141-1146
EN
The formation of thin oxide films on {111} and {110} single crystal specimens of the Fe20Cr5Al based ODS alloy during the early stages of oxidation at temperatures up to 1000 degrees centigrade was quantitatively investigated by atomic force microscopy (AFM). The AFM results revealed the crystalline character of corrosion layer. The alumina scale morphology (height and grain size of crystallites) was slightly dependent on the crystallographic texture of the underlying bulk material. The results showed that AFM is promising technique for the quantitative characterization of the surface structure of oxide layers in the initial stages of oxidation processes.
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