Characterization of the double oxide film content of liquid aluminum alloys by computed tomography

Gyarmati, Gábor; Fegyverneki, György; Mende, Tamás; Tokaŕ, M. Z.

doi:10.1016/j.matchar.2019.109925

Cited by 42 publications

(33 citation statements)

References 26 publications

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“…This technique is a relatively new melt quality assessment method, for which a detailed description is given in Ref. 8. The CT scanning of the test pieces was realized with a GE Seifert X-Cube Compact 225 kV apparatus with an acceleration voltage of 135 kV, and a tube current of 0.8 mA.…”

Section: Melt Quality Assessmentmentioning

confidence: 99%

“…5,6 The most common and, in fact, the most deleterious inclusions are the socalled double oxide films or bifilms, which have a significant impact on the structure and properties of cast alloys. [7][8][9][10][11] The formation of these defects during the liquid metal handling and processing of aluminum alloys is mostly inevitable, as any disturbance of the melt surface can cause the entrainment of the surface oxide layer. Hence, copious amounts of bifilms are introduced to the melts during typical foundry activities like melting, alloying, fluxing and pouring.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15][16][17][18][19][20][21] Besides that, bifilms can easily open up and inflate into pores because of the hydrogen diffusion into their inner gas atmosphere and the local pressure drop in the mushy zone caused by the shrinkage during solidification. 7,8,[22][23][24][25][26] These negative effects highlight the importance of good liquid metal quality control via efficient melt treatments, which aim the reduction in inclusion (especially bifilm) and solute hydrogen content of the molten alloys.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Rotary Degassing Treatments on the Melt Quality of an Al–Si Casting Alloy

et al. 2020

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In order to produce cast components, which meet the quality requirements of the automotive and aerospace industries, the control of liquid metal quality prior to the casting process is essential. Rotary degassing is the most commonly used melt treatment method in the foundry industry, which can effectively reduce the inclusion and solute hydrogen content of the metal. This procedure is often combined with fluxing, which allows more efficient inclusion removal during melt processing. In this study, the effects of rotary degassing treatments executed with and without flux addition on the melt cleanliness were compared. The quality of the molten metal was characterized by the microscopic inspection of K-mold specimens, X-ray computed tomography of reduced pressure test samples, and by Density-Index evaluation. The inclusions found on the fracture surfaces of K-mold samples were analyzed with energy-dispersive X-ray spectroscopy. Based on the results, rotary degassing coupled with flux addition can be an effective inclusion and solute hydrogen removal technique that can significantly improve melt quality. On the other hand, rotary degassing executed without flux addition can increase the inclusion content of the melts. This can be attributed to the chemical reaction between the liquid alloy and the N 2 purging gas during the degassing process. It was also found that inclusion content highly influences the tendency to porosity formation.

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Section: Melt Quality Assessmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Effects of Rotary Degassing Treatments on the Melt Quality of an Al–Si Casting Alloy

et al. 2020

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“…It is extremely important to realize the cause of poor casting quality before buying expensive additives for metal improvement and waste money on defective castings. In many works, researchers explain that the design of a proper gating system, the way that liquid metal is poured into a mold, and melt treatments are important factors that affect a casting’s quality [ 1 , 2 , 3 , 4 , 5 , 6 ]. Most of this research is based on Professor John Campbell’s bifilm theory [ 6 , 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

“…Dispinar D. et al [ 1 ] and G. Gyarmati et al [ 2 ] explained that the bifilm content in the melt is much more important than the dissolved gas content such as hydrogen, which has always been considered to be the major source of defects. They proved that with proper degassing, bifilm inclusions can be eliminated from the melt, and regardless of the hydrogen content, aluminium castings without defects can be manufactured.…”

Section: Introductionmentioning

confidence: 99%

Bifilm Inclusions in High Alloyed Cast Iron

Stawarz

Dojka

2021

Materials

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Continuous improvement in the quality of castings is especially important since a cast without defects is a more competitive product due to its longer lifecycle and cheaper operation. Producing quality castings requires comprehensive knowledge of their production, crystallization process, and chemical composition. The crystallization of alloyed ductile iron (without the addition of magnesium) with oxide bifilm inclusions is discussed. These inclusions reduce the quality of the castings, but they are a catalyst for the growth of spheroidal graphite that crystallizes in their vicinity. The research was carried out for cast iron with a highly hyper-eutectic composition. Scanning electron microscopy and EDS analysis were used in the research. A detailed analysis of the chemical composition was also carried out based on the spectrometric method, weight method, etc. Based on the obtained results, a model of spheroidal graphite crystallization near bifilm inclusions was proposed. The surface of the analyzed graphite particles was smooth, which suggests a primary crystallization process. The phenomenon of simple graphite and bifilm segregation towards the heat center of the castings was also documented.

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