The Effect of Solidification Time on the Mechanical Properties in a Cast A356-T6 Aluminum Alloy

Boileau, James; Zindel, Jacob W.; Allison, J.

doi:10.4271/970019

Cited by 47 publications

(33 citation statements)

References 6 publications

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“…This is in accordance with the results of the work of Boileau et al 153 on A356-T6 alloys. Also, more linear relations were obtained in the modified C alloy, indicating that the p-platelet size has a direct effect on ductility than in the alloys A andB.…”

Section: Alloy A3562 (Alloy C)supporting

confidence: 83%

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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Section: Alloy A3562 (Alloy C)supporting

confidence: 83%

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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“…Alternatively, with the addition of Cu, the lowest mean DAS decreased to 22 μm. This was attributed to the undercooling effect [11][12][13] achieved by increasing Cu content. The addition of Cu resulted in ner α-Al formation, which helped restrict the growth of primary Si and intermetallic phases 14,15) .…”

Section: Methodsmentioning

confidence: 99%

“…The basic microstructure of the alloys consisted of primary α-Al dendrites with eutectic Si and intermetallic particles distributed between the α-Al dendrites to form a periodic cell pattern repeated across the metallographic surface. The DAS for a given alloy composition decrease with increasing solidi cation rates [11][12][13] . In this study, the lowest DAS value for gravity die casting was 22 μm in an Al-6.0mass% Si-2.8mass% Cu alloy, as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Effect of Microstructure on High Temperature Mechanical Properties of A319 Casting Alloy for Automotive Cylinder Heads

Kim

Jeong

2016

Mater. Trans.

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A quantitative study has been conducted to evaluate the relationship between microstructural features such as secondary DAS (dendrite arm spacing), eutectic structures and the mechanical behaviors of A319 casting alloys. Depending on the cooling rate affecting the primary and eutectic microstructure, the storage elastic modulus measured by DMA (dynamic mechanical analysis) increased with decreasing DAS, with a concomitant increase in the tensile strength and elongation at RT and also high tempertures. Contrarily, the thermal expansion coef cient increased with increasing temperature, but did not vary with microstructural changes. The hardness of the eutectic phase increased with increasing DAS due to the enlarged size of the eutectic particles, whereas the hardness of the primary phase was similar regardless of DAS, owing to the precipitates that formed during heat treatment. The increase of both of LCF (low cycle fatigue) and HCF (high cycle fatigue) lives with decreasing DAS was observed, mainly due to homogeneous deformation owing to the ne size of eutectic silicon and Fe intermetallic particles. The results of fractography observation showed that ner α-Al and eutectic phases were effective to the resistance of fatigue crack initiation and propagation due to the shorter crack path along the secondary particles. The LCF lives increased with increasing test temperature according to the Cof n-Manson relation due to the larger elongation. On the other hand, an analysis of the fatigue lives with the hysteresis loop energy, which consists of both strength and elongation, showed that the fatigue lives were normalized with an alloy of the same strengthening mechanisms regardless of the test temperature. DMA analysis demonstrated that the mechanical properties of the Al 2 Cu precipitate hardened alloy were maintained at temperatures greater than 250 C, whereas degradation in the mechanical properties of the Mg-containing alloy occurred at 170 C due to coarsening in the precipitation phase of Mg 2 Si.

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“…It was found that, while fatigue life was sensitive to the maximum pore size, no relationship between pore size (as observed on random metallographic surfaces) and fatigue life was obtained. Boileau et al 63 found that porosity had a more profound effect on the fatigue life of the A356-T6 alloy. Samples with internal porosity had an approximate ten-fold decrease in fatigue life compared to porosity-free samples.…”

Section: Effect Of Porositymentioning

confidence: 99%

“…Boileau et al 63 showed that a three-fold decrease in fatigue life of A356-T6 was observed when the solidification time increased from 40 seconds (~30 jam DAS) to 1290 seconds (-90 |im DAS).…”

Section: Effect Of Solidification Timementioning

confidence: 99%

Paramètres contrôlant la précipitation et la dissolution de la phase CuAl2 du cuivre dans les alliages d'aluminium de type 319 et leurs influences sur la performance /

Li¹

2003

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The Effect of Solidification Time on the Mechanical Properties in a Cast A356-T6 Aluminum Alloy

Cited by 47 publications

References 6 publications

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

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

Effect of Microstructure on High Temperature Mechanical Properties of A319 Casting Alloy for Automotive Cylinder Heads

Paramètres contrôlant la précipitation et la dissolution de la phase CuAl2 du cuivre dans les alliages d'aluminium de type 319 et leurs influences sur la performance /

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