The Effect of Rotary Degassing Treatments with Different Purging Gases on the Double Oxide- and Nitride Film Content of Liquid Aluminum Alloys

Gyarmati, Gábor; Vincze, Fanni; Fegyverneki, György; Kéri, Zoltán; Mende, Tamás; Molnár, Dániel

doi:10.1007/s11663-021-02414-0

Cited by 9 publications

(4 citation statements)

References 53 publications

(69 reference statements)

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“…By observing contraction cavities created during the casting process, we managed to document the spatial structure of the silicon crystals of the Fe 5 Si 3 intermetallic phase. This type of analysis on surfaces of contraction cavities brings about a series of interesting results, which show oxygen inclusions [22], the participation of graphite "pushed out" of the metal bath [15], titanium carbides (TiC) [32], TiAlSi intermetallic inclusions [33], and bifilm defects [34].…”

Section: Discussionmentioning

confidence: 99%

Crystallization of Intermetallic Phases Fe2Si, Fe5Si3 for High Alloyed Cast Irons

Stawarz

2023

Crystals

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This paper presents the results of laboratory tests related to high-alloy silicon cast iron (HSCI). These materials are corrosion-resistant and commonly used in cathodic protection systems as protective electrodes. Due to their high fragility, alloys with increased Si content are not suitable for producing elements exposed to dynamic loads. This paper analyzes the crystallization process of silicon alloys (with Si content between 23% and 25%) using thermal and derivation analysis methods. The tests also included an extended analysis of chemical composition. The metallographic tests included scanning electron microscopy with an EDS system, and the phase composition was determined using X-ray diffraction. As a result of the tests, the warp components were identified, the primary share of which are intermetallic phases of the Fe5Si3 type. Moreover, single silicon crystals were found. The test results allowed for clarification of the temperature range of the transition of the Fe2Si phase into the Fe5Si3 phase and the determination of characteristic points of the crystallization process (TSolidus i TLiquidus). Furthermore, bifilm-type inclusions were identified in the alloys. We also managed to present the silicon crystals and Fe5Si3 phases in a spatial layout via observation of the surfaces of contraction cavities using scanning electron microscopy.

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Section: Discussionmentioning

confidence: 99%

Crystallization of Intermetallic Phases Fe2Si, Fe5Si3 for High Alloyed Cast Irons

Stawarz

2023

Crystals

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“…The solubility of hydrogen in aluminum is significantly lower in the solid than in the liquid state. For this reason, it is generally assumed that during solidification, hydrogen is excreted from the solution and forms hydrogen pores in the form of molecular gas H 2 [ 18 ]. Hydrogen pores cannot be formed by homogeneous or heterogeneous nucleation during solidification of aluminum alloys.…”

Section: Introductionmentioning

confidence: 99%

Aluminum Melt Degassing Process Evaluation Depending on the Design and the Degree of the FDU Unit Graphite Rotor Wear

et al. 2022

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One of the most important indicators of casting quality is porosity. The formation of pores is largely conditioned by the presence of hydrogen in the batch and subsequently in the melt. The gasification of the melt is the primary factor increasing the porosity of casts. This paper addresses the issue of reducing the melt gasification by using FDU (Foundry Degassing Unit) unit. The gas content in the melt is evaluated by determining the Dichte Index depending on the geometry and the degree of the FDU unit rotor wear. For experiments performed under the operating conditions, three types of graphite rotors with different geometries are used. The extent of melt gasification and the Dichte Index are monitored during the rotor wear, at a rate of 0%, 25%, 50%, 75% and 100% rotor wear. Secondly, the chemical composition of the melt is monitored depending on the design and wear of the rotor. It is proven that the design and the degree of rotor wear do not have significant effect on the chemical composition of the melt and all evaluated samples fell within the prescribed quality in accordance with EN 1706. With regard to the overall comparison of the geometry and wear of individual rotor types, it has been proven that, in terms of efficiency, the individual rotors are mutually equivalent and meet the requirements for melt degassing throughout the service life.

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“…Campbell [ 30 , 31 , 32 , 33 ] estimates a bifilm population of 10 6 to 10 9 m −3 in an average aluminum melt. If we assume, that each pore is initiated by a bifilm, the authors’ previous results [ 34 ] of the computed tomographic (CT) analysis of reduced pressure test (RPT) samples suggest a bifilm population of around 6·10 7 m −3 (60 in 1 cm 3 of the sample) in a highly contaminated melt. However, this could be an underestimate, as was highlighted by Tiryakioğlu et al [ 35 ], because there could be bifilms that fail to open up and inflate into pores during the solidification of RPT samples.…”

Section: Introductionmentioning

confidence: 99%

Grain Refiner Settling and Its Effect on the Melt Quality of Aluminum Casting Alloys

Gyarmati

Bogoly²,

Stawarz³

et al. 2022

Materials

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Grain refiner particles, which are intended to induce the formation of fine equiaxed grain structure during the solidification of aluminum alloys, are prone to settling during the holding of the liquid metal, which phenomenon can affect not only the grain size but the spatial distribution of the double oxide films in the melt. In this study, the settling of Al3Ti inoculant particles, as well as its effects on melt quality and grain refinement, were studied. During the experiments, the Ti-concentration of a liquid Al-Si-Mg-Cu alloy was increased to 0.3 wt.% by the addition of Al-10%Ti master alloy at different melt temperatures. Particle settling and grain size evolution were studied by quantitative metallography, while the interactions of grain refiners and bifilms were investigated by scanning electron microscopy (SEM). The evolution of melt quality was assessed by the computed tomographic (CT) analysis of reduced pressure test (RPT) samples. It was found that effective grain refinement was only realized when the introduced blocky Al3Ti particles were dissolved and re-precipitated in the form of (Al,Si)3Ti at a lower temperature. Without dissolving at higher holding temperatures, Al3Ti particle settling has taken place within 10 min. The settling of (Al,Si)3Ti particles improved melt quality by the aided sedimentation of bifilms in the melt.

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The Effect of Rotary Degassing Treatments with Different Purging Gases on the Double Oxide- and Nitride Film Content of Liquid Aluminum Alloys

Cited by 9 publications

References 53 publications

Crystallization of Intermetallic Phases Fe2Si, Fe5Si3 for High Alloyed Cast Irons

Crystallization of Intermetallic Phases Fe2Si, Fe5Si3 for High Alloyed Cast Irons

Aluminum Melt Degassing Process Evaluation Depending on the Design and the Degree of the FDU Unit Graphite Rotor Wear

Grain Refiner Settling and Its Effect on the Melt Quality of Aluminum Casting Alloys

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