Observations on the formation of ?-Al5FeSi phase in 319 type Al-Si alloys

Samuel, A. M.; Samuel, F. H.; Doty, H. W.

doi:10.1007/bf01159327

Cited by 129 publications

(114 citation statements)

References 7 publications

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“…This view is also supported by Samuel et al, 76 who found that strong linear relationships were obtained between dendrite arm spacing (DAS) and the average B-platelet length for alloy Fe levels ranging from 0.5 to 1.5 wt%. In an earlier study, Samuel et al 59 also reported that the cooling rate influences both the formation and size of the B-platelets in the alloy, with hardly any p-platelets being observed in the microstructure obtained at the highest cooling rate (corresponding to a dendrite arm spacing value of 15|im). As the cooling rate decreases, the B-platelets are observed in relative abundance.…”

Section: Effect Of Cooling Ratementioning

confidence: 99%

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Paramètres métallurgiques contrôlant l évolution microstructurale dans les alliages de fonderie Al-Si-Mg et Al-Si-Cu

Liu¹

2004

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With their characteristics of low specific gravity, low melting point, excellent castability and good corrosion resistance, aluminum-silicon (Al-Si) alloys are extensively employed in automotive applications. Castings produced from these alloys range from transmission cases and intake manifolds to more critical components such as engine blocks, cylinder heads and wheels.Two of the most popular commercial alloys used in such applications are the A356 and 319 type alloys, belonging to the Al-Si-Mg and Al-Si-Cu alloy systems. The casting quality and properties are determined by the quality of their microstructure, controlled by various parameters such as the dendrite arm spacing (DAS -as determined by the solidification rate), the degree of eutectic Si modification and grain refinement, and the amount of microporosity, intermetallics and inclusions observed in the microstructure. Among these, solidification rate is the most important, as it directly or indirectly affects almost all the other microstmctural parameters.Modification of the eutectic silicon morphology from its acicular, flake-like form to a fibrous form is usually carried out through the addition of strontium (Sr) to improve the alloy ductility. Intermetallics commonly present in these alloys are the P-AlsFeSi and a-Al 5 (Fe,Mn) 3 Si2 iron intermetallics, sludge, Mg2Si and, in the case of 319 alloys, the copper intermetallic, CuAl 2 . Due to its brittle, platelet-like nature, the P-AlsFeSi iron intermetallic can be quite deleterious to the alloy properties, as can the presence of porosity, particularly in terms of surface quality and soundness.The aim of the present work has been to investigate the metallurgical parameters controlling the microstmctural evolution of Al-Si-Mg and Al-Si-Cu alloys, through a study of the microstmctural characteristics of directionally solidified A356 and 319 type alloys as a function of iron content, Sr addition (~250 ppm), and cooling rate. The iron levels selected varied from 0.12 to 0.8 wt pet, and cover the range of Fe levels found in commercial casting alloys. The use of an end-chill mold provided different cooling rates along the height of the same casting, with DAS values that varied from ~23 to 85 |^m, corresponding to levels of 5, 10, 30, 50 and 100 mm above the chill end.The effects of these variables on the precipitation of the P-Al 5 FeSi phase, the characteristics of the a-Al dendrite stmcture, eutectic silicon modification, and porosity formation were examined in detail. Various techniques were used for microstmctural characterization and phase identification, including optical and scanning electron microscopy, electron probe microanalysis coupled with energy dispersive X-ray (EDX) and wavelength dispersive spectroscopy (WDS) facilities, and thermal analysis. An image analyzer was used in conjunction with the optical microscope for quantification purposes.

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Section: Effect Of Cooling Ratementioning

confidence: 99%

“…Samuel et al 59 found that the beneficial effect of Sr modification was manifested through its influence on the fragmentation and dissolution of the p-AlsFeSi needles. The strontium 53 was observed to "poison" the sites where "sympathetic nucleation" of the P-iron needles occurred.…”

Section: Sr Additionmentioning

confidence: 99%

Paramètres métallurgiques contrôlant l évolution microstructurale dans les alliages de fonderie Al-Si-Mg et Al-Si-Cu

Liu¹

2004

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“…70 Peyman et al phase of iron mold cast Al-6Si-3.5Cu-l.0Fe alloys. 71 Samuel et al 72 studied the effects of strontium on formation of the /?-Al 5 FeSi phase in 319 alloys. According to these researchers, the addition of strontium acts as a poison on the nucleation site of the /5-needles, thereby reducing the number of sites ultimately available for nucleation.…”

Section: Modificationmentioning

confidence: 99%

Effects of metallurgical parameters on the decomposition of л-AlFeMgSi phase in AL-SI-MG alloys and its influence on the mechanical properties /

Elsharkawi¹

2011

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“…Gustafsson et al 21 observed that the morphology of the P-AlFeSi phase is altered to Chinese script with chromium addition in an Al-7% Si-0.3% Mg alloy containing 0.52% Fe. Similar observations have been reported by Granger.…”

Section: Effect Of Other Elementsmentioning

confidence: 99%

“…In Al-Si cast alloys the presence of iron, even in small amounts, can decrease the alloy ductility considerably, due to precipitation of the (3-AlFeSi phase (details about p-AlFeSi will be discussed later) in the form of intercepted platelets. 21 The P-AlFeSi platelets act as stress raisers, which contribute to the brittleness of materials. Common sources of iron pick-up in foundry processing are from melting equipment and from remelted scrap castings.…”

Section: Iron Intermetallics In Al-si Cast Alloysmentioning

confidence: 99%

Effets des intermétalliques de fer et des porosités sur les propriétés de traction et d impact sur les alliages de coulée Al-Si-Cu et Al-Si-Mg

Ma¹

2002

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Aluminum-silicon (Al-Si) alloys are an important class of materials that constitute the majority of aluminum cast parts produced, due to their superior properties and excellent casting characteristics. Within this family of alloys, Al-Si-Cu and Al-Si-Mg cast alloys are frequently employed in automotive applications. The commercially popular 319 and 356 alloys, representing these two alloy systems, were selected for study in the present work, with the aim of investigating the effect of iron intermetallics and porosity on the alloy performance. This was carried out through a study of the tensile and impact properties, these being two of the important mechanical properties used in design calculations. Iron, through the precipitation of second phase intermetallic constituents, in particular the platelike P-AlsFeSi phase, is harmful to the alloy properties. Likewise, gas-or shrinkage porosity in castings is also detrimental to the mechanical properties. By determining the optimum alloying, melt processing and solidification parameters (viz., Fe content, Sr modification and cooling rate) required to minimize the harmful effects of porosity and iron intermetallics, and studying their role on the fracture behavior, the fracture mechanism in the alloys could be determined.Castings were prepared from both industrial and experimental 319.2, B319.2 and A356.2 alloy melts, containing Fe levels of 0.2-1.0 wt%. Sr-modified (-200 ppm) melts were also prepared for each alloy Fe level. The end-chilled refractory mold used provided directional solidification and a range of cooling rates (or dendrite arm spacings, DAS) within the same casting. Tensile and impact test samples machined from specimen blanks sectioned from the castings at various heights above the chill end provided DASs of 23-85um. All samples were T6-heat-treated before testing. Tests were carried out employing Instron Universal and Instrumented Charpy testing machines. Optical microscopy, image analysis, SEM and EPMA techniques were used for microstructural and fracture analysis.The results show that the highest cooling rate (23 urn DAS) is the most significant parameter controlling the size and distribution of the P-AlsFeSi phase and porosity in the unmodified 319.2 and A356.2 alloys. Sr modification is more effective in reducing the Pplatelet size at low Fe levels, but increases both porosity volume fraction and pore size significantly. The Mg-containing B319.2 alloy shows reduction in the P-platelet size due to its partial transformation into AlsFeMgsSiô Chinese script particles. In the Sr-modified alloys, increase in the P-platelet size is still observed at some cooling rates. Porosity volume fraction and pore size also decrease with Mg addition.

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Observations on the formation of ?-Al5FeSi phase in 319 type Al-Si alloys

Cited by 129 publications

References 7 publications

Paramètres métallurgiques contrôlant l évolution microstructurale dans les alliages de fonderie Al-Si-Mg et Al-Si-Cu

Paramètres métallurgiques contrôlant l évolution microstructurale dans les alliages de fonderie Al-Si-Mg et Al-Si-Cu

Effects of metallurgical parameters on the decomposition of л-AlFeMgSi phase in AL-SI-MG alloys and its influence on the mechanical properties /

Effets des intermétalliques de fer et des porosités sur les propriétés de traction et d impact sur les alliages de coulée Al-Si-Cu et Al-Si-Mg

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