Probing the local atomic structure of Sr-modified Al–Si alloys

Twin-controlled growth of eutectic Si in unmodified and Sr-modified Al–12.7%Si alloys investigated by SEM/EBSD

“…5b 2 ). The present result suggests that the morphology modification of eutectic Si crystals occurs at the growth stage, being realized through ''poisoning'' of twin re-entrants as proposed and verified recently by many investigations [1,18,24,25,36]. The Sr modifier can be considered to restrict further growth of eutectic Si crystals associated with the original {1 1 1} twinning planes, which is in accordance with the restricted TPRE growth mechanism [12].…”

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.…”

“…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

“…That is, over a distance of a few nanometres in front of the growth front, the local concentrations of Sr and Al are sufficiently high to allow for the formation of atomic clusters of compounds. Recently, Srirangam et al [29] showed that the local coordination environment of Sr in Al-Si alloys is consistent with the formation of SrAl2Si2 clusters in the eutectic phase supporting the concept that nanometer-sized clusters can be formed in these alloys. According to the classical homogenous nucleation theory clusters of this size are subcritical, , and the local ordering in the melt would be that of fluctuating clusters.…”