Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition

3D Atom Probe Tomography Study on Segregation of Yttrium in Modified Al-Si Alloys

“…This behavior correlates with the findings of Li et al 11 for Na modification but is in contrast to those of Srirangam et al 7 for Sr modification. Srirangam et al 7 noted segregation of Sr within the eutectic Si phase with no indication of enrichment at the interface, whereas Li et al 11 noted Na enrichment at the interface between eutectic Si and eutectic Al in Na-modified Al-Si alloys. It is therefore indicative that the phase where the additional element segregates does not necessarily indicate the modification potential of the element.…”

“…The authors further noted that the concentration of Al within the eutectic was approximately four times higher in the modified alloy when compared with the unmodified material, which further supports the hypothesis that Al and Sr are incorporated together into the Si phase in the form of nanometer-sized phases. Li et al 11 investigated the segregation of sodium (Na), another well-known modifier, in Al-5Si alloy. They noted that similar rod-like and particlelike structures formed.…”

“…Atom probe tomography (APT) has been used by several researchers to look into the segregation of the modifying element within Al-Si alloys. [7][8][9][10][11][12] Past studies have explored the application of Y as a modifier of Al-Si alloys. Researchers used varying amounts of Y, between 200 ppm and 6000 ppm, and observed that, in presence of Y, the Si eutectic forms a refined plate-like morphology rather than a fibrous one.…”

Cluster formation at the Si/liquid interface in Sr and Na modified Al–Si alloys

“…However, both cases highlight the interaction between the modifier and Si. Furthermore, APT shows that Al is present in all defects [16], even when the defect is only one atomic monolayer [18].…”

“…Recent investigations have revealed that Al forms segregations with Sr or Na in the Si eutectic phase [16][17][18]. The presence of Al in combination with the modifier was not considered in previous theories when explaining the origin of the modification [5,11].…”